Volvo 240 Alternator Page

2 4 0 T U R B O . C O M
D A V E ' S V O L V O P A G E

240 Alternator Mod Page
and my Mechman Installation

UPDATED: September 10, 2024 CONTACT

D O M A I N S

Send me an email if you have questions or can contribute to any info here.
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Alternator Idler Pulley Bracket
BASICS: How Do Alternators Work?
Poor Charging Bosch Alternators	Denso Alternators can be fitted	Denso Alternators INCREASING VOLTAGE
Mechman GM Alternator #1 First Install 2010	Mechman GM Alternator #2 2nd Install 2019	BOSCH Alternators INCREASING VOLTAGE
V-Belts Can Fail if you over-tighten	Fixing V-BELT SLIP	GM Delco Alternator Wiring and INCREASING VOLTAGE
Installing an ACCURATE VOLT METER
LARGE POWER CABLES	240 V-Belt Size Chart	AGM Batteries
Alternator IDLER PULLEY Project Details	Why not a SERPENTINE BELT?
Fitting a UNIVERSAL High-Performance Alternator into a 240

For details on the development of this project , scroll down or CLICK HERE.

240 Alternator Idler Pulley Bracket for 240 red block B21/B23/B230
for use with a high-performance alternator.
CLICK HERE for Alternator Idler Pulley Project Details

Installation guide: CLICK HERE

Questions? After you read this info feel free to CONTACT me with any questions: CLICK HERE.

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Here's a short video of this idler pulley bracket in action during my early prototype testing phase. I ran the prototype for 5,000 miles to fully test for any problems. Then later I swapped to a production bracket, which has nearly 15,000 miles with great results.
https://www.youtube.com/watch?v=-O9fC3fR4ac

BELT SLIP RESISTANCE NOTE:
After installing this on my 242, I tested the belt slip resistance by putting socket wrenches on the CRANK BOLT and on the ALTERNATOR PULLEY NUT and I applied torque to see which one would slip first. Doing this test before with the stock setup demonstrated almost NO grip on the alternator pulley. Testing with this new configuration showed that the ALTERNATOR pulley now actually had MORE GRIP than the crank pulley. Think about THAT!
This is a big change!

Some Basics: How does an Alternator Work?
Here's an entertaining video
https://www.youtube.com/watch?v=zfGm0gZhgCc

What to Do about your Old
Under-Charging Volvo (Bosch) Alternator

Here's an interesting video of the complete restoration of an old Bosch external fan alternator.
https://www.youtube.com/watch?v=eLgjyJBvYs4

And here's one that's show you a pretty good partial rebuild of a 1988 Volvo external fan alternator.
https://www.youtube.com/watch?v=6o_OrF2S_UA

How about a video showing how to remove your 240 Alternator?
https://www.youtube.com/watch?v=A72pWPYm8yo

Improving the Charge with a BIGGER/BETTER Alternator

SO, WHY WOULD YOU NEED A BETTER ALTERNATOR?
My 1984 242 Turbo originally came with a modest Bosch 55 amp alternator . Can someone explain why such a non-significant alternator was used? A non-turbo 240 got a 70 amp alternator.

In stock form, that tiny 55A alternator was barely adequate from the beginning. Like most small Bosch alternators, it suffered from a significant voltage drop when a moderate load was placed on it, especially at idle (although raising the idle to about 1000 rpm did help). And it also suffered from an even larger voltage drop when it got hot (and of course it sits next to the turbo).

The Volvo B21 (red block) engine was not originally designed to have a turbocharger when it was designed in the early 1970s. The turbocharger was added much later. I guess the Volvo engineers did the best they could. Options are few if you have a flame thrower next to your alternator, unless you want to move the flame thrower or move the alternator. They did neither.

Moving the alternator away from the turbo heat, like Volvo did in a 740, may be simpler for some people. I'll discuss that topic later in this page.
INSTEAD I decided to deal with the alternator in the ORIGINAL 240 LOCATION to see what improvements could be made.

ADJUSTABLE REGULATORS (for BOSCH ALTERNATORS)
Many years ago installing an adjustable voltage regulator helped me live with the poor charging situation by bringing up the OVERALL VOLTAGE OUTPUT, but an adjustable regulator can only do so much for a light-duty alternator.
An adjustable regulator successfully increased my beginning (COLD and NO-LOAD) voltage from about 13.5 volts to 14.4 volts. But the adjustable regulator cannot increase AMPERAGE capability and it cannot overcome a HIGH-TEMPERATURE voltage drop that's so damned common with Bosch alternators.
HOT voltage output can DROP by as much as ONE or TWO VOLTS in an old Bosch alternator!

You can read more about the reasons why your alternator has a high-temp voltage drop HERE.

WHAT HAVE OTHER CAR MAKERS DONE TO ADDRESS A HOT ALTERNATOR PROBLEM?
Porsche 944 Turbo
In the mid-1980's PORSCHE ran into a similar problem when they added a turbo to the 944 to make the 944 Turbo. There was not enough room on the exhaust side to add a turbo. There was barely enough room for a manifold. So where did the turbo go??? Have a closer look below.
This 4 cylinder engine is similar to the Volvo engine in that the intake manifold is on the LEFT and the exhaust manifold is on the RIGHT. Unlike Volvo, the Porsche engineers found NO ROOM on the exhaust side to add a turbo. Instead, they ran a pipe from the exhaust manifold, UNDER THE ENGINE, all the way to the intake side and put the turbo under the intake manifold just a few inches behind the alternator! Crazy stuff.

You can feel fortunate there were no German engineers working on the Volvo turbo engine design.

I had a discussion with a Porsche 944 Turbo owner about heat-related voltage drops. Porsche engineers did some extra work to try reducing the heat by adding a LARGE AIR DUCT to bring fresh air into the back of the alternator. This likely helped during highway speeds, but heat was still always a big problem. I don't know if Volvo engineers thought about this, but they would have had a difficult time doing something similar, unless they moved the OIL FILTER first.

CAN COOLING DUCTS BE ADDED TO A VOLVO 240 ALTERNATOR?
Yes, if you're determined enough . . . . I think it would be a great idea.
But there isn't really any room behind this 240 alternator below. Adding a shroud or duct would require relocating that oil filter first.

So if the 240 oil filter was to be re-located, maybe there could be room for something like this low-profile cooling shroud.
This shroud is Porsche PN 96410640302. I have not tried doing anything like this. If you're inspired to try it, please let me know.

Volvo (Bosch) 55 Amp versus 100 Amp
Alternator Size Comparison

The above photos show a size comparison between a Bosch 55 amp (240 Turbo) and a Bosch 100 amp (740).

Here's the bigger 100 amp Bosch alternator above that I installed in my 242 many years ago (circa 2004).
Before I owned my current 242 Turbo, I did the same installation on my old '84 245 Turbo way back in the 1990s.
I simply wanted something with more amperage, since in both cars I was using up the capacity of the 55 amp alternator and getting poor voltage, especially at idle. This Bosch 100 amp unit came from a later 700 series Volvo I found in a salvage yard. Installing one of these was a popular mod and usually helped somewhat.

HIGHER IDLE SPEED
Since even a bigger 100 amp Bosch alternator may have trouble keeping good voltage at IDLE, you also may want to consider raising the idle speed. An idle speed of about 1000 rpm can help.
The new belt size I used for the Bosch 100a unit was typically about 10 x 950 mm or slightly longer (original 240 belt size was 10 x 925 mm)

140 Amp Bosch Alternator
Wes B. sent me a photo of his alternator, which he installed in his 240. It's a Bosch 140 amp Volvo unit he bought from Ebay seller BNR Parts ebay.com/bnrparts. He has reported that it's performing well and it maintains a hot idle at 14.2 volts.

Volvo 240 Accessory Belt Sizes
Information on factory 240 accessory V belt sizes used to be easier to find, but it seems to have mostly disappeared from many useful sites.
I put this info together many, many years ago for my own 240 uses. I thought I would share it here.

ACCESSORY	Volvo PN	Size	Notes
Alternator	958352, 966908	10 x 925 mm	2 needed. 1976-83 240. Also PN 977260.
Alternator	973536, 973538	10 x 918 mm, 10 x 920 mm	2 needed. 1984-93 240. Also 9.5 x 918mm may be used in most cases. PN for these 9.5 x 918 mm belts as a pair: 973537.
			NOTE for all 240 Alternators: If you're upgrading to a larger alternator which will need more room, such as the Bosch 100A unit, you might try using size 10 x 950 mm or up to the maximum size of about 10 x 975 mm.

AC to PS	967114	13 x 1075 mm	1977-84 240. Also 12.5 x 1075 mm. PS with integrated reservoir.
AC to PS	973535	10 x 850 mm	1985-90 240 with remote PS reservoir.
AC to PS	973535	10 x 850 mm	1991-92 240 with integrated PS reservoir.
AC to PS	977759	11.9 x 835 mm	1993 240 with integrated PS reservoir.

Crank to PS (if no AC present)	966909	10 x 938 mm	1977-89 240.

Crank to AC	967103	13 x 925 mm	1976-84 240. Also PN 978678.
Crank to AC	979631	13 x 975 mm	1985-92 240.
Crank to AC	979277	13 x 938 mm	1993 240.

Here's a good video from iPd on Volvo V-Belt Basics and Identification.
https://www.youtube.com/watch?v=wsJ0ROAv6U4&t=138s

MAKING SPACE FOR THE BIGGER OIL PRESSURE SENDER
Since the Bosch 100 amp alternator case is physically a lot BIGGER than the old 55 amp alternator, it causes interference with the large 2-wire oil pressure sender found in a 240 Turbo. That brass 45 degree fitting came standard on a 240 Turbo, but the bigger alternator still hits this sender with that adapter unless you can swing the alternator outward farther.

So generally the oil pressure sender needs to be re-positioned to make more room for a larger alternator.
Sometimes finding the room for it needs some new ideas, but if the alternator can be swung out further from the engine (with longer belts) you can be successful. But this isn't always possible.

THESE PICS are from some other 240, not mine, but it shows how TIGHT THAT SPACE is for the oil pressure sender when a big Bosch alternator is mounted.

Ultimately, I dealt with the cramped space a bit differently as you can see in this image above. I mounted a "remote sender" after I had some bad experiences with other options, such as trying some adapter fittings which kept cracking from vibration. There's a longer story to this, but the short version is that this remote method actually worked very well for many years.
Here's a thread that goes over the longer version of this story and this mod in more detail:
https://forums.tbforums.com/t=192788

If you can find enough room, the ultimate position for this sender is shown BELOW, WITHOUT ANY BRASS ELBOW or ADAPTER. This would require a way to move the alternator EVEN FURTHER away from the engine.
Or a physically SMALLER alternator might work (i.e: DENSO: Click Here).

A LONGER Belt? Here's how I found there limits to a LONGER BELT.
A longer belt MIGHT have helped this installation by swinging the alternator further from the engine, which would make extra room for that oil pressure sender. But then you find that swinging the alternator further out only moves the belts TOO CLOSE to the alternator mounting bracket below.
A longer belt in this situation means the belt is going to hit that bracket. So the longest belt in this situation is probably going to be somewhere close to the 10 x 950 mm I used. That belt is about 25 mm longer than factory.

Ok then. What about a DENSO?

Here's the compact Nippon Denso alternator in a 240.
It has become popular to install this smaller case Denso alternator, which can be found in some later 700/900 models.
It's physically smaller than the above 100 amp Bosch. These Densos can usually be found in 80 or 100 amp capacity. They perform pretty much the same as a large Bosch alternator at idle.
The most positive benefit is that they do fit better. There is more room for the oil pressure sender with this more compact alternator.

Denso alternators found in Volvos are usually either 80 Amp or 100 Amp. They look similar to each other, but you'll notice the 80 Amp units have a SMALL 6 mm lug for the fat red cable. 100 Amp units will have a LARGER 8 mm lug.

Info for SERVICING A DENSO
Here's a page devoted to rebuilding a Denso alternator with more pics: https://www.volvoclub.org.uk/faq/Denso
And a discussion thread on Servicing a Denso Alternator: https://forums.turbobricks.com/t=349853

INCREASING THE VOLTAGE IN A DENSO

What about increasing voltage output for a Denso alternator like this? It's not something I have tried personally, but there now seems to be some interesting videos on this subject.
Here's one where the author increased output from 14 volts to 14.7 volts.
The video is not in English, but following along is pretty easy.
https://www.youtube.com/watch?v=HRgSHGhcolg&feature=youtu.be

INCREASING THE VOLTAGE IN A BOSCH

This is a video about using diodes to increase voltage in a later (internal fan) BOSCH alternator. It's not something I have tried personally. I've never worked on a BOSCH like this, so I would consider this EXPERIMENTAL. Make sure you read the video description so you have a good understanding before you burn your car to the ground.
https://www.youtube.com/watch?v=2PJ5i9fdbWI

Introduction of the
MECHMAN ALTERNATOR #1
This installation of my first Mechman Alternator was back in 2010**.

**MECHMAN ALTERNATOR #2 was later installed in 2019 and CAN BE FOUND BY CLICKING HERE.

Back in 2010 I finally gave up on trying to make a 100 amp Volvo Bosch alternator work to my satisfaction. Clearly, it was not going to cut it.
The biggest downfall for me was how it charged at IDLE when UNDER LOAD and HOT. When running the air conditioning (with a big electric primary puller fan and a condenser fan), voltage was suffering badly at idle and it became much worse after the alternator started getting HOT. I had begun using a big Ford electric puller fan, first trying a Ford T-bird fan from a salvage yard. I eventually changed to a Lincoln Mark VIII (Mark 8) fan. A Mark VIII can pull up to 40 amps at full speed, but full speed isn't really needed very often. But even a raised idle speed of about 1000 rpm couldn't bring voltage up enough for my happiness.

More info on the big Lincoln Mark VIII cooling fan setup and other electric fan ideas can be found in my Electric Fan Page HERE .

.
My Intro to Mechman
So, in 2010 I was introduced to Mechman high performance alternators by a Turbobricks member.
I then talked with Mechman and I told them about my low idle voltage. I was assured that a custom unit they would send me would improve voltage at idle by offering more amps at idle. Mechman didn't really have a high-performance Volvo-specific alternator, so they custom tailored a GM Delco style alternator to fit a Volvo.

Skipping ahead: The 2010 Mechman alternator did improve charging at idle and overall output was much better, but it STILL suffered from an annoying voltage drop when it got hot. The voltage drop was not as bad as the Bosch though, but I still had to resort to keeping my idle up a bit higher than normal to keep charging voltage from dropping off below 13V when everything was on.
I began thinking there might NEVER be a real solution for a 240 Turbo with the alternator on the hot exhaust side and I thought I might have to eventually move the alternator to the other side of the engine like on the Volvo 740.

SPOILER UPDATE: August 2019
I learned in 2019 that Mechman no longer offers CUSTOM FIT alternators like the one I bought below. It was customized (machined by Mechman) to properly fit a Volvo red block.
BUT, I have since found there are STILL pretty simple solu tions to make a universal high-output alternator fit your Volvo.
I've added info that should help do this. CLICK HERE.

BOSCH ALTERNATOR VOLTAGE DROPS
With the BOSCH 100 amp alternator, the voltage drop between COLD and HOT with a heavy load at IDLE was:
14.4 volts COLD to 12.4 volts HOT.
A FULL 2 VOLT DROP! Unacceptable.
Also this situation was forcing me to set the idle speed higher than it should be to help keep voltage from going through the floor.
Here's a temperature reading from my exhaust manifold (AT IDLE) a short distance from my alternator.

WHY DOES CHARGING VOLTAGE DROP SO MUCH?
(SPOILER: It's ultimately about the WARRANTY)
The reason is that the design of an automotive alternator, specifically the design and efficiency of the copper windings, has a direct effect on the deterioration of current output as temperatures increase. This is partly due to increased resistance in the copper windings as temperatures increase. This deterioration could be corrected by design, however increased current output always increases internal temperatures even more.
Heat is the biggest enemy to alternator long life,
so alternator engineers needed to compromise and they have simply prioritized the designs of alternators to have the best chances of surviving a WARRANTY PERIOD.
Specifically allowing an alternator to reduce output when it gets hot is the answer to that compromise. So there's really not much else you can do with a standard Bosch automotive alternator if it's getting hot and dropping voltage. Volvo did add a thin heat shield for the 240 Turbo. It probably helped slightly. This is not as much of a problem in cars where the alternator is on the opposite side from the exhaust, like in the Volvo 740 or 940.

Isn't there a temperature sensor in an alternator that helps to regulate current output?
With regard to old Bosch alternators that we find in our old Volvos, the answer is NO. There is no temperature regulation in the alternator or in the voltage regulator (except of course the common deterioration of efficiency with higher temps as mentioned above). There are more modern alternators made now, which have internal temperature sensors, but that never existed for the old Bosch units in a 240 or 740.

What about the battery temperature sensor found in some Volvo 740s?
From 1985-87 some Volvo 740s came with a special voltage regulator, which was connected to a temperature sensor mounted under the battery. See the images below. This sensor was there to measure the battery temperature, not the alternator temperature. Additionally, this system did not compensate for high under-hood temps. It was designed to elevate alternator voltage 0.5 volt when it detected extreme cold ambient temps.

FIRST GM MECHMAN 2010 MORE DETAILS

Here's the Mechman alternator from 2010 compared to the Bosch 100 amp I was using up to that time.
The Mechman used a large case GM Delco style housing. This particular alternator had its case slightly modified by Mechman to fit better in the factory Volvo mounting location (while also using a few spacers). I was told this Mechman unit was created as a one-off 170 amp alternator based on the Delco AD230 (which was reportedly in a 1996-2013 GM truck). This alternator is used in vehicles which DO NOT have an ECM or computer controlling alternator charge output.
This unit from Mechman had a little custom machining to its case at a mounting location so it would bolt up similar to the Volvo Bosch alternator.
More about the machining modifications Mechman did can be found HERE.

Similar Volvo conversions have been done using GM AD244 and GM DR44 late model truck alternators. The reported benefit is better output at idle, which is something the old Volvo Bosch unit don't do well.

4-POLE ALTERNATOR PLUG INFORMATION
This alternator will have a 4-pole connector for the regulator. Note: The P-L-F-S pin designations below are also sometimes called P-L-I-S.

This connector can be found fully assembled with wire pigtails as PN 110-12046.
If you need the connector housing only or the terminals and seals separately, search for:
Metri-Pack 4-Way connector, Aptiv (Delphi) PN 12186568.
Female terminal 17-20 AWG, Aptiv (Delphi) PN 12048074.
Wire Seal Aptiv (Delphi) PN 15324976.
Sealing Plug Aptiv (Delphi) PN 12059168.

More info: www.dirtydingo.com/ID=108

Here's what the above GM Mechman #1 (from 2010) looked like installed in my car.

The belt size I typically used for the Bosch 100a was 10 x 925 mm or 10 x 950 mm.
I found that if I could swing this Mechman slightly further from the engine, I could eventually fit a 10 x 965 mm.
The limiting factor was always the lower part of the alternator bracket where you can see the belt getting close.

GROUND CABLE When Using a GM Alternator
Attaching a big ground on this alternator was a bit different that the old Bosch. It didn't come with a ground stud on its case, so the solution (also suggested by Mechman) was pinching a ring terminal against the case underneath as shown here. It turned out to be a good solution as long as that long bolt doesn't tend to loosen over time. I used a good lock-nut on that long bolt to make sure it didn't vibrate loose.

The best charging results with this new (2010 Mechman) alternator came after I added a dedicated 4 GAUGE ground cable and positive cable DIRECTLY from the alternator to the battery. You can see the results of numerous tests in the above mentioned installation thread. I still experienced a pretty significant COLD-to-HOT VOLTAGE DROP using this alternator, but ultimately adding these cables provided the best result so far for any alternator I had tried up to this time.

Using enhanced (LARGER) POSITIVE and NEGATIVE Cables .
The latest version I did on my car uses FAT FINE STRAND, high-flex WELDING CABLE. Welding cable uses very small wire strands, making a large, fat cable much more flexible.
Why do you need flexible cable? I'll tell you why.
My first cable version used large, fat normal strand cable. The vibration and flexing of the fat power cable at the alternator eventually broke the cable at the alternator lug after a number of years and many miles, leaving me stranded and calling for a tow truck. Plan ahead and get better cable.

This illustration ABOVE will give you an understanding of the enhanced power and grounds that are recommended with a high-amp alternator. You might consult the manufacturer of your alternator for a cable size recommendation, but be prepared to be told to make them very BIG. I made this illustration above to show the big dedicated cables (POWER AND GROUND) going directly from the BETTER TO ALTERNATOR and a big cable from the BATTERY TO STARTER. The factory used a cable going between the alternator and the starter. This become unnecessary. Using a cable there was convenient for the Volvo factory, but it's better to ALWAYS use cables directly from the battery to the component.

<<< WARNING NOTE: I don't recommend using one of these inexpensive disconnect devices on your battery when using a high output alternator like this. I had one of these on my negative battery terminal back in 2010. After installing the Mechman I began experiencing some strange intermittent momentary voltage drops when the alternator was under load, such as when the AC was on. It took a while to figure it out and it's detailed in the Turbobricks thread mentioned above. It turned out that this disconnect knob was creating higher resistance in the ground cable circuit and the Mechman was sensitive to it. I removed this devise so that my battery ground was solidly connected.

DEALING WITH BELT SLIP
Belt Slip is the Unintended Side Effect of a HIGH-PERFORMANCE ALTERNATOR

Have a good look at the belts wrapping around this pulley. There's just a little more than 90 degrees of belt wrap.
The actual belt-to- pulley contact patch is pretty small. But that's how a 240 is designed. This is not very good and it's why the designers added DUAL BELTS.

This was not really a problem back when the weaker 55 amp original Bosch alternator was there, but it became intolerable with a high output alternator.

I found that I needed to tighten the alternator belts much more and then they usually needed more tightening later as they began to wear. I was putting a LOT of stress on my belts. That can cause problems.

BROKEN BOLT

That bolt on the front of the block for the adjusting bracket has been known to break off (it happened to ME).
I've also heard of a few people with broken water pump pulleys (see thread here: https://www.forums.turbobricks.com/t=323223).
Over-tightening a V-belt is just plain BAD. It can also prematurely wear water pump bearings and generally your belts don't last as long as they should. They just wear faster and then they begin slipping again sooner.

MORE ON THE BROKEN BOLT ISSUE WILL CONTINUE LATER IN THIS PAGE.

Belt Failure Concerns from Over-Tightening.

This was NOT an alternator belt. This was a 240 crank pulley to AC compressor belt.
It failed after about 300 miles of use because it was adjusted too tight. The belt didn't actually break, but it did jump off the pulleys after breaking those reinforcing cords.

That long corded string stuff above was the embedded cord in the top-side of the belt. The cord separated from the belt (or maybe snapped from too much tension) and then eventually unraveled. The belt eventually came off the pulleys and I found it sitting in my belly pan. Most of that corded material ended up wrapped around my AC pulley. Once that corded part separated, the belt lost the ability to stay tight. After losing that corded material, the belt became more like a big, soft, stretchy rubber band.

MECHMAN #2
Updated 2019: I Got a New BIGGER/BETTER Mechman

Wiring a GM Mechman	Increasing Voltage in a GM Alternator
PLFS 4-Wire Plug Info	GM Voltage Regulator

In 2019 I installed a Mechman #2 for the 242.
This one is physically about the same size as the previous Mechman, but it's much "beefier" on the INSIDE.
This alternator came with a 170 amp 6 phase HAIRPIN STATOR.
According to the literature a bit further below, it's based on a GM Delco CS130D (original to a 1998-2002 GM F-body, i.e.: Camaro).
This alternator is used in cars which DO NOT have an ECM or computer controlling alternator charge output.
This Mechman part number was B8206170M (PN B8206 with 170 amps).

The alternator Mechman provided for me was custom prepared by them for a VOLVO.
This means they did some MINOR MACHINING to the case so it would easily bolt up in the Volvo red block mounting location similar to a normal Volvo Bosch alternator. And of course it also got a double V-belt pulley instead of a serpentine pulley, since the 240 uses V-belts.
More on the custom modifications that were done to create this alternator can be found HERE.

UPDATE NOTE about custom Mechman availability: August 2019
In 2019 I learned that Mechman no longer offers CUSTOM FIT alternators to directly fit a Volvo. This customization was done to my alternator. More about this is further down in this page.
So are the custom features really necessary? The answer is NO!
There are great solutions to make a UNIVERSAL high-output alternator fit your Volvo.
I have added info below that will help. CLICK HERE.

Before getting this alternator I had no clue what a 6 PHASE HAIRPIN STATOR was. Now that I know, I'm here to say that if you upgrade to a high-performance alternator, buy one with a 6 Phase Hairpin stator.
There's info below that will show you how different a 6 phase hairpin stator looks and performs compared to a normal 3-phase type.

So, the 6-phase hairpin design looks pretty cool.
. . . but does it actually perform better?
YES IT DOES. Keep reading below.

WIRING a GM Mechman
I've added some information below on how the WIRING is done for this alternator or for ANY GM style alternator with a similar 4-pole plug.

More info below on the P-L-F-S connector.

. Here are a couple ways to connect an alternator like this.
You have undoubtedly heard of 1-wire alternators. Forget what you heard. This is NOT a 1-wire alternator.
A true 1-wire alternator is considered self-exciting and doesn't require an external circuit source to excite charging. The GM CS130D requires an external source to excite it (similar to a Volvo Bosch).
In most OEM systems, this excite circuit is the wire to the dash battery warning lamp. Same with Volvo Bosch. In this example below, a resistor is used in lieu of a lamp.
Note: P-L-F-S plug pin designations are sometimes called P-L-I-S.

Resistor. 470 Ohm 1/2 W Carbon Film Single Resistor.
www.amazon.com/WWNKYZX7ES9QZMTDZ693
The polarity for a resistor is not specific. A resistor can point either direction.
If you're familiar with the old Bosch alternator, it used the red D+ wire from the dash charge warning lamp to excite the charging. The GM CS130D is not very different. This method above is pretty standard for this type of alternator, which uses this the P-L-F-S plug.
With this method above the “L” (Lamp) terminal is connected to switched 12v, with a resistor in-line to reduce current to the regulator. The resistor will offer a similar effect as a warning bulb, except with this method you will not have a dash warning lamp that will illuminate if the alternator fails. Either way, the resistor is important. Many on-line sources say that if you do not use a resistor on this circuit, you may eventually burn up the voltage regulator.
The 12 volt switched source needs to be powered when the key is in the "RUN" position. This will activate the alternator when the engine begins running. It must be a switched circuit, because if a constant 12v circuit was connected, it would eventually drain your battery after the engine was shut off.

ALTERNATIVE using two Excite Circuits

An alternate method of exciting the alternator is shown above. This method offers two redundant ways to excite the alternator. Plus it offers an opportunity to have a normal dash warning lamp if you want one. The lamp used in a dash lamp is normally a very low wattage incandescent bulb (1 or 2 watts). The bulb will offer a small amount of resistance, which will serve protect the regulator in the same way as the resistor method above. The alternator doesn't need very much resistance to excite and a 1 or 2 watt bulb is perfect. Some sources say the minimum trigger to excite might be as low as 1/4 watt.
The only downside to using a bulb to excite the alternator is if it burned out, the alternator may stop charging without warning. Fortunately, this above method also offers a redundant way to excite using the 'F' terminal. The "F: terminal is also connected to switched 12v. No resistor should be used with the 'F' terminal wire.
More info: www.dirtydingo.com/shop/ID=108

.VIDEO: Activation of GM style alternator with P-L-F-S plug.
Here's a video that demonstrates the use of the above 470 Ohm resistor INSTEAD of a bulb.
https://www.youtube.com/watch?v=a3pp448t0U4

Resistor. 470 Ohm 1/2 W Carbon Film Single Resistor.
www.amazon.com/dp/WWNKYZX7ES9QZMTDZ693
The polarity for a resistor is not specific. A resistor can point either direction.

VIDEO: Here's a tricky method designed to BUMP UP VOLTAGE in any GM style alternator that has an 'S' (Sense) terminal.
This method may work for any other alternator which uses an S terminal. This method uses diodes. Mods like this are at your own risk.
https://www.youtube.com/watch?v=qLX-RBcsNrU

In the above video he is using the following resistor and diode below:

Resistor connected to the "L" wire: 470 Ohm 1/2 W Carbon Film Single Resistor.
www.amazon.com/dp/B07QYRRX3L
The polarity for a resistor is not important. It can point either direction.

Optional DIODE connected to the "S" wire: 1N5404 Rectifier Diode 3 amp 400V.
www.amazon.com/BOJACK-Rectifier
The polarity for a diode is important. The silver band needs to point TOWARD the ALTERNATOR.
Here's another video below discussing the above 1N5404 3 amp Diode connected to the 'S' wire where an increase of about 0.3 volts per 3 amp diode is demonstrated (results can vary).
https://www.youtube.com/watch?v=MRoJMv-yMSY

Alternately you may use one or more 1N40001 - 1N4007 1 amp Diodes instead of a 3 amp if you feel like experimenting for different voltage results.
1 amp Diodes are featured in the next video below.

POTENTIOMETER METHOD TO INCREASE VOLTAGE
Here's another method designed to bump up voltage output in an alternator with an 'S' (Sense) terminal.
This method uses a 5k Ohm POTENTIOMETER and optional 1 amp diodes. NOTE: Mods like this are at your own risk.
https://www.youtube.com/watch?v=QEIpHnuj6sc

This video above is very brief and explains things rather quickly. I made a diagram below that will help. The 1 amp diodes are optional. He explains that these diodes are in place to offer a default voltage setting that will be ABOVE the normal setting, which only comes into use in case the potentiometer circuit fails. So you could try out one, two or three diodes there to see what that setting would be.

At the end of the above video he says, "This is effectively a $5 external voltage knob, not $80." I think the $80 knob he is referring to is a 5k Ohm potentiometer that is a ready to use device and sold as the Brand X Voltage Control Knob: https://brand-x-electrical.com/ . If you're looking at ready-made control knobs, that might be a solution. Or you could consider one from Coventry Car Audio, which offers a control knob with a voltage display:
https://www.coventrycaraudio.com/. If you use one of these ready-made devices, you'll see in their instructions that you should use the optional relay.

4-POLE ALTERNATOR PLUG INFORMATION
This plug connects to the regulator and would be typically found in a 1998-2002 GM F-body (Camaro), 2004-2005 Buick or Pontiac, and 2001-2006 Cadillac.
Fits alternator part numbers: Denso 104210-3060, 104210-3070, 104210-3300, 104210-4540; GM 15145637, 25697765, 25697766, 25758348, 25759776, 84009369.
Note: The P-L-F-S pin designations below are also sometimes called P-L-I-S.

More info: www.dirtydingo.com/ID=108

DELCO VOLTAGE REGULATOR

If the voltage regulator ever needs to be replaced in this CS130D type Delco alternator, I thought I would add that info here, just in case it becomes useful to you (or me) in the future.
12 Volt, B-Circuit, S-F-L Terminals, 15.0 Voltage Set Point, w/ LRC For Denso Alternators.
Part Numbers: Denso 126600-0030, 126600-0031, GL10031, 104210-330, 104210-454, Transpo IN6003.

Installing an ACCURATE Voltage Meter.
Anyone can install a volt meter. But THIS section will discuss my work in getting a really, really ACCURATE volt meter, after many years of having a NOT so accurate one.
Working toward an extremely accurate volt meter might seem a bit obsessive, but if you've read this page, you can easily come to a conclusion about THAT.
If you have used the factory VDO VOLTS gauge, you know it's not known for being precise or even CONSISTENT.
The below info will detail how I did this project in my 240 and the results. As you'll see I have a few suggestions, but this certainly is NOT the only way to do this. I welcome your comments.

Over the years I've tried a few of these digital meters instead of a VDO volt gauge. The most common ones are like this 3-digit LED meter below. They work fine and can found on-line cheap. I prefer a digital meter anyway. But is a digital meter accurate?

AND this time I wanted to step up to a 4-DIGIT LED DISPLAY (with 2-digits to the RIGHT of the decimal).

THE KEY: A MORE DIRECT PATH FROM THE ALTERNATOR
This 4-digit unit has three wires instead of two wires. You can see the meaning of that third wire in the diagram below. I connected both power wires to power.
Meters like this can be found by searching for 4-digit DC volt meter. Having 4-digits does NOT make this more accurate. What makes it accurate is the more DIRECT path from the alternator to the meter. A typical in-dash volt gauge doesn't have a direct path at all. Not even close (see here about "path"). The factory gauge will have a number of connections between the battery/alternator and the dash. So it suffers dramatically from voltage loss.

The PATH in this diagram above from the alternator to the volt meter is pretty direct. The only thing in it's path is a standard mini RELAY.
Without that relay, the alternator "S" Sense circuit would be active all the time when the car is off. Also the meter would be on all the time. That can drain the battery and it's kinda bad to do that. So the relay is there to activate things when the car is running and to shut it all off when the car is OFF.

The factory path of the wiring for a 240 volt gauge is by using power and ground in the dash. That dash power comes through a number of different wires and connectors between the battery and the gauge. That will cause a voltage drop.
Let's see how complicated the PATH normally gets for a volt gauge in a 240.
Beginning at the battery, there's a wire going to a junction block on the inner fender. From there, a wire goes back to the firewall, into the under-dash area, terminating at a pole on the ignition switch. This is where battery power is switched to ON for things in the dash that don't have full-time voltage. From the ignition switch, another wire runs to the fuse panel. The circuit will then probably go through a fuse (possibly fuse 13), and then a new wire goes to a multi-pin plug near the instruments. From that connector a power wire is shared by several gauges.
CHASSIS GROUND: And using a normal chassis DASH ground is fine for most devices, but it may not provide as clean a path as a direct ground wire from the battery or the alternator.

CONSISTENT READINGS
I mentioned consistency early in this article. Why?
My testing has suggested that volt meter readings can be more consistent when very little load is present, but when load increases, consistency changes, sometimes a lot. We know using power-hungry accessories will pull voltage down in most Volvo 240 systems, but does that always mean the battery or alternator output is being pull down equally. My tests say NO. This type of inconsistency can fool your volt gauge into registering less voltage than your system has at your battery or alternator. This will be more easily explained in a video I'll post here soon.

Here are some photos showing my wiring.
The first image below shows the PLFS plug on my Mechman GM alternator.

The second image below is an Amp AT connector for those same wires as the run to the right fender. The wires then go back to the firewall and into the dash.

This image below is the new 4-digit meter installed at the base of my center dash console. Is that reading 14.77 volts? Yes. That's the actual alternator output.

More coming . . .

MORE GM MECHMAN GENERAL INFO

The GM Mechman I'm using is this one above, PN B8206170M. The '170' in the PN is the amps. The 'M' is a machined finish.

This style alternator is also available in 240 amps and in a BLACK finish, such as the PN B8206240B pictured below.

Note about the alternator POWER OUTPUT lug:
In this photo above you can see the B+ output lug may be pointed to the rear or to the side. I'm using one that's pointed to the rear.
If requested, Mechman offers the option of either configuration.

HAIRPIN STATOR
(This info taken from a MECHMAN page)
6 Phase Advantage

Mechman Elite and S Series alternators employ cutting edge alternator technology not found in other aftermarket alternators. 6 phase hairpin stators make Mechman Elite and S Series alternators fundamentally more efficient than other aftermarket alternators. This new technology and increased efficiency equates to incredible output at extremely low engine RPM, less energy wasted in the form of heat, and more horsepower to the wheels. Also because less heat is being generated, the internal components of Mechman Elite and S Series alternators last longer. This is especially beneficial on turbocharged and/or endurance racing vehicles with high engine compartment temperatures. All Mechman Elite and S Series alternators feature soldered stator and rectifier connections, with epoxy re-enforced stator connections, reducing the chance of vibration failures.

High Pole Count

Mechman Elite and S Series units are built exclusively with precision balanced low-mass rotors that allow them to operate safely at shaft speeds of 20,000+ rpm. This high RPM capability, combined with excellent output at idle, gives the user a much broader operating RPM range, and more flexibility in the size of the crankshaft pulley used. A properly selected Mechman Elite and S Series alternator can even fix low voltage problems caused by using small diameter, or "underdriven" pulley ratios. The higher pole count in the rotor also results in less electromagnetic interference to cause problems with radios and other electronics.

Twin Rectifiers

As a final precaution, Mechman Elite and S Series alternators are constructed with twin high efficiency cooling fans, and twin internal rectifier plates. While other high performance alternators have only one rectifier with 6 diodes. Mechman Elite and S Series units boast 12 press fit diodes with 300% more surface area to dissipate heat. These considerations to cooling airflow and heat dissipation make Mechman Elite and S Series high performance alternators the most durable aftermarket alternators you can buy. If you are experiencing pre-mature alternator failure, intermittent electrical accessory problems, or low voltage at any engine RPM, a Mechman Elite or S Series alternator is the answer!

Parts Comparison: 6-Phase High Output MECHMAN versus 3-Phase
https://www.youtube.com/watch?v=LMB2Rrpz9yg

6 PHASE HAIRPIN STATOR
P E R F O R M A N C E

Here are the dyno specs for this 6 phase alternator, Mechman PN B8206170M. As you can see it puts out 145 amps at idle and 185 amps while cruising.

That sounds impressive but what does that mean in real life?

IT MEANS THIS:
Now, when I first fire the car up cold, the voltage output is ~14.8 volts. As things warm up, it slowly settles to about 14.5-6 volts.
So then what if I turn on accessories, like EVERYTHING you can think of: AC and high wattage headlights, etc.
With the old 100 amp Bosch, this would create a HOT voltage drop of up to 2 volts.
With this Mechman it STAYS VERY STABLE with a voltage drop of up to about 0.2 volts (at the battery), even when HOT and even during hot IDLE!
Alternator voodoo like this has never happened to me before! Certainly never with a Bosch.

ALMOST NO VOLTAGE DROP WHEN HOT!
Impossible you say? I would have doubts too if I didn't see it for myself.
So yes, if you can afford it, buy a 6 phase hairpin stator alternator.

And this video shows the fully HOT alternator voltage when getting a full load.
https://www.youtube.com/watch?v=T5c_6JGEplo

While the above reading may seem deceiving, the actual voltage drop measured at the battery is shown below.

IDLE SPEED
I've mentioned in a couple places in this page that I've had to increase my idle speed to improve charging. This was a must when I was using a BOSCH alternator and back then I had to keep idle at 1000 RPM.
With a Mechman this can be a subject to pay attention to also, but it's not as big an issue.
Every car is not the same. My 1984 240 Turbo factory idle speed is 900 RPM. I run my car at about 950. That's a bit higher than most normal 240s. Most non-turbos recommend 750 ±50 RPM. I know some MECHMAN users are running their idle below 700-800 RPM, but I think that 700 might be pretty much as low as I would go with a Volvo 4 cylinder and with an alternator like this. You'll find there's a certain RPM threshold where charging begins to drops off if you dip too low, so adjust accordingly.

MECHMAN versus Other Performance Alternators
Mechman 6-phase alternators are not cheap, but they have very high quality. Be careful if you begin looking at no-name or Chinese made high-performance alternators. Mechman made a comparison video showing how cheap some of the fake "high-amp" alternators can be:
https://www.youtube.com/watch?v=j5l4z3b2zHA

Mechman has options for adjusting voltage if you need that. I ultimately found that it was NOT needed for my installation, since my alternator stays put at full voltage under all load conditions.
If you're interested in Mechman alternators, you can find them at: https://www.mechman.com/

CS130D Disassembly, Rebuild
If by chance you're playing with GM CS130D alternators, I found the below video, which details the disassembly and rebuilding of one. I found it pretty interesting and decided to put it here in case it becomes useful for someone.
https://www.youtube.com/watch?v=hdK8ZqNvGsc

Up next:
Seriously Dealing with the
BELT SLIP ISSUE
and the reason for the
ALTERNATOR IDLER BRACKET PROJECT.

CHIEF SYMPTOM:
Incurable Belt Slip during High Load.
The 240 original alternator design doesn't offer enough BELT WRAP (belt to pulley contact) for an alternator which can push a heavy load. Volvo engineers added a second belt to the 240, which makes it better than one belt, but when you exceed the grip capacity for those belts, it's just going to slip.
I spent more time than I should have over the years, trying different belts and cranking them tighter and tighter.
In the end, I STILL HAD BELT SLIP.

Photo above showing how MY ALTERNATOR looked with POOR BELT WRAP: After installing this new Mechman high-performance alternator in 2019 I found I needed a lot more belt grip. This was an immediate problem when running my AC and cooling fans.

So my idea to FIX BELT SLIP was to design an IDLER PULLEY.
(technically a back-side idler)
My goal was to significantly increase belt wrap on that alternator pulley.
A back-side idler is NOT normally done with V-belts. Some people will say you shouldn't try it. Some of those people will also tell you the Volvo engineers knew what they were doing when they made the 240, so you shouldn't try to improve anything. I say the Volvo engineers made a COMPROMISE, which only works (marginally) if you keep your car original and you can be happy with 12.8 volts or less.
The main concern against a back-side idler seems to be the potential for faster belt wear. Well, crap! I already had faster belt wear because I was over-tightening my slipping alternator belts and replacing them way too often to keep fresh grip.
And so far all of these "concerns" appear to be based on opinion, not actual experience. I have not found ANYONE who has attempted this.
So if this concerns you, wait and see how this turns out.
Let's Begin.

HERE'S MY ORIGINAL MOCK-UP CONCEPT WITH AN IDLER PULLEY

Observations and Rationalization:
I found there wasn't enough room for a pulley between the crank pulley and alternator unless the alternator was moved over about 1 to 2 inches.
A bracket (shown above) could also include the BONUS of a mounting point for the upper adjuster bracket. This would eliminate the need for a new longer custom upper adjuster bracket.
This also eliminates the bolt going into the front of the block, which so often BREAKS OFF!
And after a careful look under my hood, I could see there was actually decent room in my 240 to move the alternator over, away from the engine.
Nothing interferes (if you have metal oil cooler pipes, CLICK HERE).
And this provides a lot more room for the oil pressure sender.
Let's proceed.

WAIT! WHAT ABOUT A SERPENTINE BELT?
This kind of thing below has been considered.

First, let's look at how the Volvo 850 and 960 serpentine belt was arranged. All of the accessories were designed to be on ONE side of the engine.
The water pump on this motor is turned by the timing belt, so it's not involved with the serpentine belt.
And here's an observation: the BELY WRAP on this alternator above is TERRIBLE.
So let's pause for a minute and I'll explain why I DID NOT pursue this .
I've seen a few people do variations of serpentine systems in Volvo 240s, but so far I have not seen anyone do it for a 240 with proper pulleys for an alternator, water pump, power steering and AC using actual RED BLOCK accessories OR with a PROPER TENSIONER PULLEY, which is certainly recommended.
Yes, you can cobble together some pulley parts from a salvage yard and adapt them, but you will still need a custom crank pulley (for B21). Or for a B230 you'll need a custom B230 crank dampener (see HERE). And you will STILL have to make all of the needed brackets to hold those idler pulleys and a tensioner.
So yes, it could be done, but it would be VERY expensive.

In the end, after all this work, can you get better belt-wrap on the alternator this way?

Building a custom serpentine system can be mind-boggling. This isn't a Volvo below. It's an interesting project. It's a 7 part video project on all the work this guy did to get all these accessories to work. This photo is from part 7: https://www.youtube.com/watch?v=Sh61f7U9RHc

If you're still thinking about a serpentine and you have a B230, KL Racing has a set of serpentine pulleys that might work, as long as you don't need power steering or AC.
https://shop.klracing.se/sv/artiklar/multiremhjul-sats-volvo-b230-8v.html

This 740 style idea has also been suggested:

Below image from 700 900 Specification D24, D24T, TP30518 pg 117.

"Why don't I just give up and change to a 740/940 style alternator mounting?"
I don't think there's really anything wrong with changing your 240 to the 740/940 style alternator mount. You just need the parts. It requires new mounting brackets, maybe a new 740/940 style power steering pump and new or modified power steering hoses. Plus changes to the alternator cables/wires. The only question I still have is about potential belt slip. Yes, this arrangement offers more belt-wrap on the alternator pulley than a normal 240, but it allows for only ONE alternator belt.

Mechman has an FAQ page: www.mechman.com/faqs/ and they have something to say about BELT SLIP.
"Single V belt and 4 rib serpentine belts will start to slip at about 150 amps worth of load. For minimal belt slip, 240 – 370 amp alternators should not be driven by anything narrower than a 6 rib serpentine or a dual-V belt drive setup ."

So, would that ONE ALTERNATOR BELT really be good enough for a high output alternator?
Some cars may be different, but I can tell you that I have tried using just one belt with my idler pulley setup and I'm 100% certain one belt is NOT BE ENOUGH with an alternator as strong as mine.

PROTOTYPE TESTING BEGINS
INITIAL IDLER BRACKET DESIGN

Test Engine #1 B230:
For those who don't have a 240 nearby to look at, here's a view of the STOCK alternator pulley belt wrap situation. Of course the alternator pulley slips. Look at that belt wrap.
This belt wrap on the alternator pulley is bad-bad-bad.

Stock Early 240 Alternator Mount Detail
More original 240 bracket and tensioner arm info can be found in the installation guide below.

FIRST Plastic Prototype on Test Engine #1 B230:
So I started by making a bracket out of CARDBOARD (not pictured).

Then I made a prototype bracket from PLASTIC (that's the PHOTO ABOVE) .
This is 1/4 inch PVC I bought from McMaster Carr. It's easy to cut or grind and can easily be bent with some heat. This material made it easy to make adjustments when test fitting over and over on an engine, which in this case was on an engine stand. This plastic bracket was pretty rigid and easily strong enough to mount an alternator and try out some belts.

Here's the plastic prototype bracket mounted on a B230 test engine with an idler pulley and belts.
Moving the alternator about 1.5 inches away from the engine did not seem to be a problem. In my 240 there seemed to be plenty of room. That amount of spacing allowed for the alternator to swing for a good adjustment range.
And the nice side-effect is there's now a LOT MORE ROOM for the oil pressure sender.

OIL COOLER PIPES CLEARANCE
On the subject of moving the alternator away from the engine, there is a possibility of interference with original steel oil cooler pipes if your car has them, but I think interference can be fixed if it does happen. I removed those pipes on my 242 years ago when I changed to a remote oil filter and larger oil cooler. Details about this change can be seen in my OIL COOLER PAGE.

In the photos above, the oil pipes appear close to the bottom of the alternator bracket, but probably not so close that they would interfere when the bracket is moved outward. But every car may not be the same, so study your pipes if you have them.

On this 240 ABOVE, owned by Vincent M., a high-performance 240 amp Mechman alternator has been fitted (Mechman PN B8206240B). My idler pulley bracket was installed and the alternator was spaced away from the engine 1.5 inches. The oil pipes in this car were not original to this car. He installed them from used parts. Vincent found them to be quite close to the bottom of the alternator. Some bending of the oil pipes has been done and more could be done to create clearance. The oil pipes are pretty strong and carefully bending them can be done with good results. Otherwise, there are certainly still options to use other oil hoses if needed.
SIDE NOTE: Vincent is using a smooth surface idler pulley found HERE.

WATER PUMP HOSE CLEARANCE
Here a photo below showing the top clearance between my alternator and my water pump hose. It's roughly about 3/4 inch from the alternator at it's closest.

CLEARANCE Between Alternator and Frame
Here a photo below showing the side clearance between the alternator and frame after 1.5 inch spacers were added.

Again, the Plastic Prototype on my Test Engine #1 B230:

I wanted this new bracket to be able to use the stock top adjuster bracket (tensioner arm) that I was using.
This is why I added a mounting ear to the bracket.
The top adjuster bracket on my 1984 car is an early one. A later 240 is different. I'll discuss different tensioner brackets later in the installation section.

If you have ever experienced the bolt for the adjuster bracket BREAKING OFF in the BLOCK (like I have and many others have), then you'll appreciate that the design of this new bracket eliminates the use of that bolt forever.
I have a section in this page on this subject HERE.

By the way, here's a video below showing how to repair this broken bolt if this happens to you.

https://www.youtube.com/watch?v=Zb9TxJsa1as

Then I had a steel bracket made.
STEEL PROTOTYPE BRACKET #1:

I had a working prototype made by a local metal fab shop using 1/4 inch steel plate.

And I bought some steel spacers.

These particular spacers shown are 1.5 inches long and 7/8 inch in diameter.
PN 4GVD9 from Grainger.com.

Here's a photo showing how much bolt thread usually goes into the Volvo block ( B21/B23/B230) when using a stock alternator bracket. There's about 14-15 mm of bolt thread sticking past the bracket.
The threaded holes in the block are usually about 15-16 mm deep, so your original bolts use up most of that thread depth. The factory aluminum bracket is 15 mm thick at these holes, so your stock bolts are most likely M8 x 1.25 x 30 mm long.
BOLT LENGTH NOTE: A 30 mm bolt length is measured NOT COUNTING THE BOLT HEAD in case you're curious.

Keep this info in mind when deciding how long of a bolt is used if you add an idler pulley bracket and decide to do your own custom spacers. In my case the spacers were 1.5 inches long. The new steel idler pulley bracket is 0.25 inch thick. The combined total was 1.75 inch (44 mm). So if you used the same size spacers as I did, you would be using bolts with a length of about 75 mm (not counting the head).

CAUTION: Always test your bolts in the block to check for the fit. If you think they might they bottom out before the bracket is tightened, you can add a washer or two.

Another photo of the Steel Prototype #1 with pulley on Test Engine B230 #1:

Here's the first test-fitting of the STEEL prototype bracket and pulley.
You may have noticed that I changed to a different idler pulley in this photo ABOVE. There's more info below on this different pulley.

Again, Steel Prototype on Test Engine #1 B230:
Here's a view of the back-side. The mounting ear can be seen here for the top adjuster bracket.

CHOOSING AN IDLER PULLEY

This is the first idler pulley shown in the above prototype pics. I chose it mainly because I wanted to use a smooth pulley with side flanges. It was not expensive, HOWEVER, I had some concerns about the durability of this pulley, since it was originally intended for a lawn tractor. I couldn't find any useful specs other than what I have listed here, so I have no real reason for having doubts, except that it just might not be designed for a car engine. So after thinking it over, I decided instead to choose an idler pulley that was actually designed for automotive use at higher engine RPMs, high temperatures, etc.

DUAL BEARING PULLEY
I found this polymer (plastic) pulley listed in the Dayco Pulley Guide (PDF link below). So I ordered one.
Yes, it's a GROOVED pulley. Keep reading for that.

Dayco offers a good variety of pulleys and the below guide lists a lot of them, but relatively few are "FLAT" or SMOOTH pulleys and some ahve side flanges. And even fewer are WIDE ENOUGH for TWO V-BELTS (it should be more than 1 inch (26 mm) wide), but I think getting one at least 30 mm wide like this one would be best.

The majority of the pulleys that Dayco offers are grooved pulleys, which are designed for a grooved serpentine belt. All of these pulleys have sealed ball bearing centers, but there is a variety of center bore diameters. Some in the catalog have a 10 mm center hole (like THIS one) and some have 17 mm center holes (and a few other center hole sizes are found). I preferred a 10 mm center hole. It's a good size for a standard sized 8 mm bolt.

The majority of the pulleys they offered had ONE center bearing. Very few had DUAL BEARINGS. An automotive grade pulley with a single bearing would probably be just fine for this project, but I decided since something with two bearings was available, I would try that.

There were concerns about using a pulley with RAISED GROOVES. The concern was about the back-side of a v-belt running on a grooved surface potentially damaging the belt. I tested this using Gates belts for over 5,000 miles, my conclusion is it worked OK, but it does eventually cause some wear damage to the belt. More details and photos below CLICK HERE.
CONCLUSION: Grooves should be avoided. More below.
Dayco Pulley Guide PDF: daycoaftermarket.com/PULLEY-DIMGUIDE.pdf
Dayco Main Page: https://na.daycoaftermarket.com/en/

WIDER DUAL BEARING PULLEY

I have not tried this one. If I did I would remove the grooves and make it a smooth pulley.
This polymer (plastic) pulley is similar to the above Dayco 89516, except it's wider and has larger 17 mm center bearing holes. If you chose this pulley and wanted to use an 8 mm bolt in the center, you would need to buy some center bushings that could be tapped into the holes to reduce it to 10 mm. Two center bushings would be needed to pressing into the center. More on those bushings can be found HERE.

There are concerns about using a pulley with RAISED GROOVES. The concern is about the back-side of a v-belt running on a grooved surface potentially damaging the belt. I tested this using Gates belts for over 5,000 miles, my conclusion is it worked OK, but it does eventually cause some damage to the belt. More details and photos below CLICK HERE.
CONCLUSION: Grooves should be avoided. More below.

Dayco Pulley Guide PDF: daycoaftermarket.com/PULLEY-DIMGUIDE.pdf
Dayco Main Page: https://na.daycoaftermarket.com/en/

Steel Prototype modded and fitted to Test Engine B230 #1:

After initial testing, I decided to make an adjustment to the position or height of the idler pulley.
I raised the idler pulley up more in order to increase belt-wrap around the alternator pulley even more than I had. As you can see in this pic, there is now more than 180 degrees of belt-wrap on the alternator pulley.
Then long term testing was done with this configuration in my 242.

Here's the modded steel prototype bracket installed for long-term road testing on Test Engine #2 B21FT in my car.

I installed the bracket in my 240 Turbo for long-term road testing and I put thousands of miles on it with no problems.
If this bracket looks a little different, YES, this prototype was modified a couple times before settling on this configuration.
Belts: GATES METRIC-POWER XPZ 1120
The belts I used FIRST (shown above) were Gates Metric-Power XPZ 1120 . These are 1120 mm in length, 10 mm wide. They have a cog on the bottom.

VERDICT:
This idler has SOLVED all belt slip problems on my 242.

WHAT ARE THE EFFECTS OF
USING A GROOVED IDLER PULLEY?

Installation and testing on the B21FT:
Lets discuss how THE GROOVES affected the belts.

BELTS: GATES METRIC-POWER XPZ 1120
These are 1120 mm in length, 10 mm wide. They have a cog on the bottom.
The only effect that was been found with these belts was some marks caused by the grooves in this photo above.
The grooves etched some lines onto the backs of the belts. This began to appear after only a few miles and then after well over 5,000 miles it did not change much. It may look bad, but it did not become a serious problem with THESE BELTS. Changing to a SMOOTH pulley is a much better idea. I'll be showing that below.

SMOOTHING THE GROOVED PULLEY
There is a smooth pulley available shown further below, but I still have a preference for the DUAL BEARING pulley that I used above (DAYCO 89516). But I concluded it needed to be SMOOTH. So I decided to modify it.
I used my bench grinder to slowly grind down the raised grooves. I allowed the pulley to slowly spin on a bolt while slowly grinding. So basically I turned this into a much smoother pulley. It only took 10 minutes. Worked perfectly.

Trying some different belts.
ALTERNATE BELTS (Engine #1 B230 pictured).
I bought a set of the belts shown here to test as an alternative.
USING the STEEL PROTOTYPE BRACKET

This is a Dayco Top-Cog belt.
It comes as a Top-Cog as shown with a normal bottom 'V' section in 0.44 inch (11 mm) width. This 11 mm width will fit the 10 mm wide pulleys in a 240 just fine.
Note that since this belt is 1 mm wider, it will make the belt ride slightly higher in the pulley groove, which can make the belt seem a bit shorter than a 10 mm belt.

Construction and internal reinforcement images for Dayco Top Cog.
After trying these belts, I found that I liked them because they seem to have more internal reinforcement than the Gates belts.

CAUTION: Make sure to get MATCHED BELTS.

Here's something to be aware of. The belts I tried above are 1120 mm long , DAYCO TOP COG PN 15440. I ordered them through Summit Racing ($12 each). Keep in mind that you need to buy belts like this as a MATCHED PAIR. I had a bad experience with the first order and I got un-matched belts. The belts in the above photo are un-matched because one belt is slight less wide than the other. It meant that only one belt will be tight. This caused a belt slip problem.
Summit Racing corrected this problem right away when I called them and they sent me new matched belts. www.summitracing.com/15440
So if needed, you might need to talk to someone in-person and ask them to send a matched pair.

Also keep in mind that this TOP COG may have changed to a NORMAL COG. More recently I have ordered the same Dayco 15440 part number and they turned out to be normal BOTTOM cog types like this below

SMOOTH SURFACE PULLEY
So after about over 5,000 miles of testing with the grooved pulley, I decided I would try out this smooth pulley to see how things went.
As expected, the smooth pulley worked perfectly. No issues st all.
Ultimately, I went back to the DUAL-BEARING pulley (and I ground the grooves smooth). I just liked the idea of dual bearings better.

Dayco Pulley Guide PDF: daycoaftermarket.com/PULLEY-DIMGUIDE.pdf
Dayco Main Page: https://na.daycoaftermarket.com/en/

PULLEY CENTER BORE: This polymer (plastic) pulley above only comes with a 17 mm center bore. Also it's a little larger in diameter than the other pulleys I tried. The outer diameter is not a problem.
I designed the idler bracket to use a smaller 8 mm bolt, so the 17 mm center hole is too big on this pulley. So I bought one of the below pictured center bushings and installed it into the center of this pulley. These bushings have a 17 mm outside diameter and a 10 mm (0.375 inch) center bore and they are a nice snug press-fit into the center bore of the 17 mm bearing on this pulley. No press was needed. I just tapped it in with a hammer.
Cost was small for this bushing. About $3 to $10: mrmowerparts.com/idler-bushing, amazon.com/B00AZ0OPPQ/, ebay.com/itm/176372873805.
If you're searching, look for a 17 mm x 3/8 inch bushing for belt pulley.

Customer Vincent M. used this smooth pulley in his 240 project. See BELOW PICS. His alternator is Mechman PN B8206240B, which is an all black version with 240 amps.

Installation Guide
for the IDLER PULLEY BRACKET

As you can see here, this bracket has been made for a wide range of adjustments for different size alternators, different size idler pulleys, different positions for the pulleys and different positions for the top tension adjuster bracket, etc.
The below photos show the installation into my my 1984 240 Turbo B21FT.

For my installation I used the below style of TENSION ADJUSTER BRACKET. A particular style is not requi red. You can use any style that you have. This FIRST IMAGE below is the typical bracket found on early B21 or B23 equipped 240s up to about 1985. This is the same as bracket #3 in the bracket assortment photo below.
Tension Bracket, Volvo PN 1276128.

This SECOND tension adjuster bracket type below has a tension adjusting bolt. This type of bracket was found in B230F equipped 240s from 1985-93. This is bracket #4 in the bracket assortment photo below.
Tension Bracket, Volvo PN 1346365.

Here's a photo ABOVE from a TB thread showing an assortment of Volvo tension adjuster brackets that were offered for 240 and 740. The usual 240 brackets shown above are #3 (early) and #4 (later 240).
https://forums.turbobricks.com/t=356867

Here's another view ABOVE of the LATER STYLE 240 TENSION BRACKET (Style #4) mounted in the usual factory location.

UPDATE 2023: I have acquired the below style tension bracket and when I have some time I'll be experimenting with it. This bracket is similar to the #4 later style bracket above, but clearly a bit different on the bushing end. When I complete these experiments, I'll post that info here. Volvo PN 1346024 acquired from iPd.

The PULLEY I ultimately stayed with is Dayco 89516. I chose this one because it has dual bearings and fits perfectly. I don't think dual bearings is a must, but I just like stronger options where there is one.
I smoothed out the grooves on this pulley with my bench grinder to provide a smoother surface for the back side of the belts to ride on. More details about this pulley can be found HERE.

There is more than one choice of pulleys. You can also choose a pulley that already has a smooth surface, but it will not have DUAL bearings. See that one HERE.
Dayco Pulley Guide PDF: daycoaftermarket.com/PULLEY-DIMGUIDE.pdf
Dayco Main Page: https://na.daycoaftermarket.com/en/

The bolts I used below were M8 thread that I pulled from my spare bolt bin. I think the length of that pulley bolt is about 50 mm. I spaced the pulley away from the bracket using a couple washers and it has about 1/8 inch clearance from the bracket.
IMPORTANT: Be sure to use LOCKING NUTS here. Normal fasteners can vibrate loose over time and that would not be good.
There are many choices for a good lock-nut. If you're using M8 bolts, the lock-nuts pictured below are these from iPd: https://www.ipdusa.com/products/11455/.

I checked both the B230 and B21 blocks to see how deep the threads are for the alternator bracket. Both were about 15 mm deep as shown by the grease marking on the below bolt. Keep this in mind during your installation. You should try to get at least 10 mm of bolt thread inserted during your installation, but your bolts should not be so long that they bottom out before becoming tight. If a bolt you choose is close to being too long, you can always add a washer.

HARDWARE TO MOUNT THE BRACKET: I used 1.5 inch long steel spacers and 75 mm long bolts (M8 x 1.25 x 75) bolts with washers (pictured below). The bolt length is measured without the head.
These bolts pictured are strong Grade 10. I recommend Grade 10 because of the long length. Grade 10 bolts are used in the kit here.

But if you use your own bolts and you only have Grade 8 bolts, they should be ok. I tested the prototype bracket for over 5000 miles using Grade 8 bolts. This included several different dis-assemblies and re-assemblies. Not a problem.

ABOVE PHOTO: I received some feedback from a customer who used shorter 1 1/8 inch spacers instead of 1 1/2 inch to add a little more clearance to oil pipes and the results were good. The alternator in this photo is the Mechman B8206240B , which is similar to mine, except it has 240 amp capacity and is BLACK in color.
If you decide on a different length spacer instead of 1.5 inches, then you should change your bolt length.

OPTIONS FOR PULLEY AND TENSION ARM HOLE POSITIONS

I designed this to have many options for the mounting locations for the pulley and tension arm.
The current positions that I am using for my 240 are: Pulley Hole #2 and Tension Arm Hole A.

BELT OPTIONS
GATES METRIC-POWER XPZ 1120
The belts I used FIRST were Gates Metric -Power XPZ 1120. These are 1120 mm in length, 10 mm wide. They have a cog on the bottom.
MATCHED BELTS.
Gates supposedly matches their belt lengths, so when ordering these in pairs you SHOULD get matching length belts.
www.amazon.com/Gates-XPZ1120
Matched belts seems like a no-brainer, but some belt vendors DO NOT offer this and I have had frustrating problems before with mis-matched belt pairs. If a mis-match occurs, it will usually be because one belt it slightly WIDER, which makes it slightly shorter when sitting in a V-pulley groove.

DAYCO 15440 1120 mm
I also tried using the below Dayco Top Cog belts. I liked these belts also because they have more inner reinforcement than most other belts.
The belts I used are 1120 mm long , Dayco PN 15440. I ordered them through Summit Racing ($12 each).
MATCHED BELTS.
Keep in mind that these should be matched in length and width. Some places will send you un-matched belts if you don't specifically ask for a matched pair. You definitely don't want one belt longer (or slimmer) than the other. It has happened to me. So try to talk to someone in-person or by email and ask if they can send a matched pair. Summit Racing did this for me.
www.summitracing.com/15440

DAYCO 15435 43.5 inch (1105 mm)
Web B. told me he used the Dayco 15435 belts when he installed this idler bracket. A shorter belt like this will swing the alternator a little closer toward the engine.

.
POSITIONING AND INSTALLING THE NEW BRACKET

Above left photo: With the alternator and original bracket removed and out of the way, I first positioned the new pulley bracket against the engine block over the mounting holes. I loosely threaded in one SHORT original bolt into ONE of the holes to hold the new bracket in place. This is only to hold the bracket so it doesn't fall and knock you on the head when you let it go. Plus it helps a lot when you're inserting the stock alternator bracket, spacers and long bolts one-by-one while you have only two hands. You can remove that short original bolt after getting one of the long bolts started through the factory bracket and spacer and into the block.

ALIGNMENT

Before tightening the bolts, pay close attention to the alignment of the idler pulley. Check it from below and above. It needs to be lined up and pretty close to being CENTERED on the two rear belt grooves on the crank pulley. Also the idler pulley should be straight, or at about the same vertical angle as the crank pulley. If you have a short bubble level you can compare the vertical angle of the crank pulley with the angle of the idler pulley. Try to make them the same.

INSTALLING BELTS
When I install these belts, here's the technique I use, in case this helps you. This image below is me installing Dayco 15440 belts, 1120 mm. I do this one belt as a time. First I install a belt over the water pump, crank and alternator inner pulley groove, WITHOUT wrapping it around the IDLER PULLEY. Then the final step is pushing the belt over the idler pulley while the alternator is pushed inward. The I do the same for belt #2.

SETTING PROPER V-BELT TENSION
Most DIY Volvo owners don't have special belt-tensioning tools. So my best technique for setting v-belt tension is the same 90 degree flex method that's demonstrated in this belt video.
https://www.youtube.com/watch?v=FMiB3CnZpRc

Or use this image below as a guide for deflection on the longest length. This image is from the 1984 240 7,500 mile maintenance service manual.

Also keep in mind that you should re-check belt tension after a period of use, perhaps after a few hundred miles. Brand new V-belts will often get a little looser after a period of use and I have found that they often need to be re-tightened.

TIGHTENING MY BELTS
Since I use an early style tension adjustment arm, I use a simple pry bar behind the alternator to pull the belts tight before tightening the final bolt. Here's what that typically looks like.

Here's a customer bracket installation which was used mainly to eliminate the Problem of a Broken Bolt in the Block

If you have ever experienced a sheered off bolt in the front of the engine block like this below, this section will concentrate on THAT PROBLEM.

A few customers have asked if they could use this idler pulley bracket to replace the adjuster mounting point where that bolt commonly breaks in the engine block.
The below photos were sent by Tyler W., who experienced MULTIPLE broken bolts there. So he mounted the new idler pulley bracket with spacers for just the purpose of eliminating the need for a bolt in the block.

Tyler originally wanted to try to use the bracket without an idler pulley, because he wasn't using a high-amp alternator. Eliminating the idler pulley may be possible, but Tyler found that the 1130 mm long V-belts he bought created some interference between the belts and part of the original bracket under the belt (near that lower alternator bolt). I believe Tyler might have avoided the use of the idler pulley by using a shorter belt, which I think would probably allow the alternator to tilt upward enough to gain belt clearance away from that bolt.

FITTING A UNIVERSAL HIGH-PERFORMANCE
ALTERNATOR TO A 240

In August 2019 I learned that Mechman no longer offers specially customized alternators made to directly fit a Volvo red block. They do, however still offer a wide variety of alternators, including the same model I bought, but they just don't want to deal with customizing them for a Volvo. It turns out the customizing part was actually pretty minor. I'll show that below in detail. It's not absolutely needed.
So it's certainly still possible to fit a great high-performance Mechman alternator to your Volvo.

When searching for an alternator style you can use, It's my opinion that you should look for something with mounting points similar to the original Bosch. In other words, you might choose something similar to the below LEFT image as opposed to the below right image.

So Mechman chose an alternator configured like this below.
This particular alternator was chosen by Mechman because the mounting points were somewhat close to the Bosch mounting points. Keep in mind that they are somewhat close, not precisely close.
It turns out that SOMEWHAT CLOSE will be just fine for a Volvo.

Then they altered the aluminum case at that top 2 inch thick flange by machining the back surface of that TOP 2 inch dimension. This is where your tension adjuster bracket attaches. They reduced the thickness there from 2 inches to 1.25 inches. There's more detail below, but that machining does NOT really HAVE to be done to fit this unit into a Volvo. I'll show you.
Then of course they also replaced the serpentine belt pulley with a dual V-belt pulley. That's pretty much it for any mods.

The Mechman pictured below left is believed to have originally begun as a Delco AD230 for a 1996-2013 GM truck.
The Mechman #2 that I installed later in 2019 (CLICK HERE) was originally designed from a Delco CS130D for a 1998-2002 GM F-body (Camaro). So If you buy a Mechman alternator or a high-performance alternator from another company, you can use this information as a guide to help you find a model that will fit a Volvo.

Lets discuss the above dimensions.
DIMENSION A is the mounting flange for the alternator to factory engine bracket. Rubber bushings and a long 8 mm bolt (13 mm head) are used. The Bosch alternator fits just right in that factory bracket, but as you can see the Mechman dimension A is 3/4 inch smaller. Spacers were used for the Mechman in my car and you can see that in an image HERE.

DIMENSION B is the thickness of the mounting flange for the top adjuster bracket. This was modified on the above Mechman.
This Mechman originally began with this flange being 2 inches thick (Dimension D). Mechman custom machined the case so this flange was reduced to 1.25 inches thick. That reduction brought Dimension D very CLOSE to the same as the Bosch Dimension B (which is 1 inch thick). This modification worked fine, but as I recall I did still needed to make some sort of adjustment to the top adjuster bracket to deal with the 1/4 inch difference. I think I probably flipped the adjuster bracket 180 degrees or I inserted the rubber bushing on the other side. There are a few tricks like this to make the alignment better on an early bracket. Ultimately it worked just fine.

DIMENSION C is the distance between the two mounting points. The above Mechman is 1/2 inch shorter than the Bosch for Dimension C. This ultimately made NO difference at all.

So, is machining an alternator case really needed?
No! As mentioned above, it's NOT needed.

I did a bunch of measurements and determined that an UNMODIFIED non-Volvo alternator (like a Delco above) can be made to fit very well if your top tension adjuster bracket is MOVED back a bit. The easiest method I know to do that is to install one of my idler pulley brackets, which allows for this very thing.

So if you choose an alternator which has that thicker Dimension B (such as a Delco unit for GM truck or Camaro mentioned above), you COULD go to the trouble of disassembling it and having the case machined like Mechman did. . . . Or if you don't want to do that, and if you are considering using one of my idler pulley brackets, have a look at the below images.

These images above shows the top adjuster bracket mounted in the NORMAL location for an alternator with dimensions similar to the Bosch. So then this configuration worked for me with an alternator that was modified like Mechman did. (NOTE: That's a Bosch 100A in this photo above).

Now have a look at this change below. . . .

This is an early Mechman in these photos ABOVE. It's possible to mount the top tension adjuster bracket to the REAR or BACK-SIDE of the bracket mounting ear as shown.
I have demonstrated this by inserting a spacer at the alternator to simulate a thicker, unmodified alternator flange (Dimension B) with a full thickness of 2 inches, like it was before it was ever machined by Mechman.
So just like that, fitting an unmodified Delco style Mechman or other alternator is possible without a lot of fuss.
And there is STILL a lot of room for the oil pressure sender!

SOME CUSTOMER PHOTOS BELOW.

ABOVE THREE PHOTOS: I received some photos and feedback from a customer who used this Mechman B8206240B alternator, which is nearly identical to mine, except this one has 240 amp capacity and is BLACK in color.
NOTE: This alternator ABOVE was not modified to fit a Volvo. It was installed with the top tension adjuster bracket positioned on the REAR of the idler pulley bracket mounting ear. It fits very well.

Also you can see this alternator has the large OUTPUT LUG pointing to the SIDE, instead of pointing to the rear like mine. Mechman can offer a choice when you place an order.

Also keep in mind that the "CLOCKED" position of the back 4-pole connector plug and output post can be changed or rotated relative to the alternator mounting position.
I discussed this partial disassembly procedure in the following thread beginning at Post #41: http://forums.turbobricks.com/t=350085

V-BELT PULLEYS
When considering an alternator that you think will work, the next important thing to determine is if it can be fitted with a V-belt pulley.
Most alternators for cars made in the last 20 years will probably come by default with a SERPENTINE belt pulley.
V-belt pulleys are widely available for almost any alternator and you just need to make sure there's one available that you can use or there is one that you can customize if a stock one is not available.
The original 240 double V-belt pulley is made to fit 10 mm wide belts.
The below photo shows three different double V-belt pulleys.

The LEFT pulley is an original pulley for a Bosch (Volvo) alternator using 10 mm wide V-belts. This is from an old 100A alternator.

The MIDDLE pulley is for a Delco alternator using 10 mm V-belts. This came on my first Mechman.

The RIGHT pulley is for a Delco alternator using 13 mm wide V-belts. This came on my second Mechman.

The difference does not look very large in the photo, but it might make a difference if use a 13 mm pulley with 10 mm belts. It might be OK, but I preferred to use the correct pulley for the V-belt width if possible. Maybe the different V angle could promote BELT SLIP if it doesn't match perfectly (???). I don't know. I have used a 13 mm pulley before and it seemed ok. If you decide to use a 13 mm belt pulley with 10 mm belts, let me know how it works out for you.

SELECTING A SUITABLE V-BELT PULLEY
Since I became a bit obsessive about a good fitting pulley, this is an issue that I needed to deal with when I installed the latest Mechman #2 in 2019. I'm posting this just to show that sometimes unexpected problems come along and this is how I solved this one.
The above MIDDLE Delco 10 mm pulley (same as this one below) was originally supplied by Mechman with the first Mechman #1 alternator I bought back in 2010 ( based on a Delco AD230 alternator for 1996-2013 GM truck). This pulley worked fine on that early Mechman. The part number for this pulley is 24-1101 (or 241101). It can also be identified as Delco 1846787, 1964758, 1968354, 1970830, or Ford C5AZ-10344-L, C5TF-10A352-K2, C9AF-10A352-C, E4TZ-10344-B, E6SF-10A352-AA, E6SZ-10344-A, GP494, GP617, GP629.
FYI: This type of pulley is also generally characterized by the 13 mm dimension from the back flange to the center of the first groove (refer to the pulley diagram below).

When Mechman shipped the latest alternator #2, which I installed in 2019 ( based on a Delco CS130D for a 1998-2002 GM F-body car), it came with the ABOVE RIGHT Delco pulley, which is made for wider 13 mm belts. That pulley *might* be OK for 10 mm belts, but I was stubborn and decided instead I wanted a proper 10 mm pulley.

The first thing I did was to try to fit the above middle 10 mm Delco pulley (24-1101) on the new Mechman. It did actually go on (the alternator has the same 17 mm shaft diameter), however the shaft length on the new alternator was shorter. It didn't stick out as far. That made it impossible to use that pulley in stock form. The shorter shaft meant the 16.5 mm flange dimension in the ABOVE diagram was a bit too thick and the large nut holding the pulley on could not be threaded on enough. I was getting about 1 turn on the nut. Not good enough.

CUSTOM SOLUTION
The solution I chose was having a 24-1101 (10 mm) pulley custom machined. This means that I had the inner recess cut deeper to reduce the 16.5 mm flange thickness to 12 mm. You can see the difference between this image below and the above one. That solved the problem and allowed me to use the Delco 10 mm pulley. The diagram below shows the MODIFIED dimensions for this pulley.

AND THEN I LATER FOUND THIS PULLEY.
Here's a possible alternate 2-groove pulley I found later, but I have NOT tried fitting one of these.
It's made for 10 mm belts. It has a slightly larger outside diameter, 75 mm instead of 67 mm, but I think it might be worth trying if you would rather not go to the trouble of having a pulley machined/modified. I think this one could possibly be mounted with the addition of one or two washers behind it to get proper spacing out, away from the alternator case, since there is no flange/shoulder sticking out on the back side on this pulley.
This pulley is PN 24-3105 (or 243105). Chrysler PN 5227174 for Chrysler 40/90, 50/120A alternators. Chrysler, Dodge, Plymouth 1987-1989. The center hole is made for the same 17 mm shaft diameter, so I think it may fit with some luck.
If you try one of these, please let me know how it works out.

Here's a good selection of 2-groove pulleys, all machined from cold-rolled steel .
alternatorparts.com/2-groove

AGM BATTERY
For my Volvo I use the below AGM battery.

This is the Super Start Platinum from O'Reilly Auto. The Volvo 240 uses Group Size 34, which uses the above specifications.
An AGM battery means it's constructed using Absorbed Glass Mat, which is superior in design to an old school flooded lead acid battery.
I picked this battery because it's made by East Penn Manufacturing, who has been known for making the revered Deka battery line. I've been very happy with this type of AGM in my cars for many years.

ALTERNATOR CHARGING VOLTAGE
The Mechman alternator I use typically charges between 14.3 and 14.7 volts when things are good and hot and stable. This seems to be OK for this AGM Battery, certainly not excessive. Most high performance AGM battery manufactures warn against overcharging using a battery charger (usually not above 14v). Charging with a battery charger is not the same as ALTERNATOR charging. Most published recommendations for alternator charging are between 13.8 and 14.8 volts, while some will recommend up to about 14.6 volts. Interstate Batteries recommends not over 15 volts for an AGM.
Keep in mind any of these recommendations always comes with temperature variables, so try not to take them as absolute. For example, you can see how recommended charging voltages will change dramatically depending on temperature in XS Power's AGM guidelines. Most guidelines will agree that ALTERNATOR charging below 14 volts is getting close to insufficient for a battery like this.

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