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240 Alternator Mod Page

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Bosch Alternator
Denso Alternator
Mechman Alternator Upgrade
Belt Failure
Belt Slip

Alternator Idler Pulley Project Details
Fitting a Universal High-Performance Alternator

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

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

Installation guide: CLICK HERE

 
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2 4 0    A L T E R N A T O R    M O D    P A G E
What to Do about your Old Under-Charging Volvo 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




2 4 0    A L T E R N A T O R    M O D    P A G E
Improving the Charge with a Bigger/Better Alternator
 
WHY WOULD YOU WANT OR NEED A BETTER ALTERNATOR?
My 1984 242 Turbo originally came with a modest Bosch 55 amp alternator. In stock form, it was barely adequate from the beginning and like most light-duty Bosch alternators, it suffered from a significant voltage drop when a moderate load was placed on it, especially at idle.  And it suffered from a larger voltage drop when it got hot (and of course it sits close to the turbocharger). 

The Volvo B21 red block engine was not originally designed to have a turbocharger. The turbocharger was added much later and I guess the Volvo engineers did the best they could. Not much can be done if you have a flame thrower next to your alternator, unless you want to move the flame thrower or move the alternator. 
Moving the alternator may be easier for some people.  I'll discuss that topic later below. 
For now I'm dealing with the alternator in the ORIGINAL LOCATION
and we'll see what improvement can be made.



Installing an adjustable voltage regulator helped me live with this situation by bringing up the overall voltage output, but an adjustable regulator can only do so much. The adjustable regulator successfully increased my beginning (COLD) voltage from 13.8 volts to 14.4 volts.  But the adjustable regulator could not increase amperage capability of the small alternator and it cannot overcome a high-temperature voltage drop (except of course in part by increasing the overall beginning cold voltage setting). The voltage output could drop by more than a volt when the alternator became HOT.

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




WHAT HAVE OTHER CARS MAKERS DONE TO ADDRESS THE HOT ALTERNATOR PROBLEM?
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. 
This engine is similar to the Volvo engine in that the intake manifold is on the left and the exhaust is on the right.  Unlike Volvo, the Porsche engineers found NO ROOM on the exhaust side to mount a turbo. Instead, they ran a pipe from the exhaust manifold, UNDER THE ENGINE, all the way to the left side and put the turbo under the intake manifold right behind the alternator!  Crazy stuff.
You can feel fortunate there were no German engineers working on the Volvo turbo engine.
     
I had a discussion about similar heat-related voltage drops with a Porsche 944 Turbo owner.  Porsche engineers did something extra to reduce the effect by adding a large cool air duct to bring air into the back of the alternator. This likely helped during highway speeds, but it was still always a big problem.
Volvo engineers would have had a more difficult time doing something like this, since the oil filter was in the way.





Volvo (Bosch) 55 Amp versus 100 Amp Alternator Size Comparison
    
Here's the bigger 100 amp Bosch alternator BELOW that I installed in my 242 many years ago (circa 2003). Before I owned this car, I did the same installation on my old '84 245 Turbo way back in 1997. I simply wanted something bigger than what I had, since in both cars I was using up the capacity of the original 55 amp alternator and getting poor voltage, especially at idle. This 100 amp unit came from a later 700 series Volvo I found in a salvage yard. Installing one of these was a popular mod back then.
The belt size I used for the Bosch 100a unit was in the range of 10 x 925 mm to 10 x 950 mm.





Volvo 240 Accessory Belts
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
966908
10 x 925 mm
2 needed. 76-83 240. Also PN 977260.
Alternator
973538
10 x 918 mm
2 needed. 84-93 240. Also 9.5 x 918mm.



NOTE for all 240 Alternators: If you're upgrading to a larger alternator which will needs 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
77-84 240. Also 12.5 x 1075 mm.
AC to PS
973535
10 x 850 mm

85-92 240.

AC to PS
977759
11.9 x 835 mm
93 240.




Crank to PS (no AC present)
966909
10 x 938 mm
77-89 240.




Crank to AC
967103
13 x 925 mm
76-84 240. Also PN 978678.
Crank to AC 979631
13 x 975 mm
85-92 240.
Crank to AC 979277
13 x 938 mm
93 240.




<<< Since the Bosch 100 amp alternator case is physically BIGGER than the old 55 amp alternator, it causes interference with the large 2-pole oil pressure sender found in turbo 240s.  That brass 45 degree fitting came standard on 240 Turbos.


<<< So generally the oil pressure sender needs to be re-positioned to make room.  Sometimes finding the room for it is difficult, but if the alternator can be swung out further from the engine (with longer belts) you can be successful. <<< THESE PICS are from some other 240, not mine, but it shows how tight the space is for the oil pressure sender when a big alternator is put in there.


Ultimately, I dea
lt with the cramped space a bit differently by trying a remote sender installation.  It actually worked very well.
Here's a thread that goes over this in more detail:
https://forums.tbforums.com/showthread.php?t=192788



<<< If you can find enough room, the ultimate position for this sender is shown here, WITHOUT THE BRASS ELBOW, but this would require some planning to get the alternator further away from the engine and/or a smaller alternator is needed.


<<< 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 moves the belts TOO CLOSE to the alternator mounting bracket. 

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, which I used.  That belt is about 25 mm longer than factory.



2 4 0    A L T E R N A T O R    M O D    P A G E
What about a DENSO?
<<< Here's the Nippon Denso alternator in a 240.  It has become popular to install this smaller case alternator found in later 700/900 models. It's physically smaller than the above 100 amp Bosch. These Densos can be found in 100 amp or higher capacity. They perform pretty much the same as a large Bosch alternator at idle. The positive benefit is that they do fit better.

There is usually more room for the oil pressure sender with this more compact alternator.
Here's a page devoted to rebuilding a Denso alternator with more pics: https://www.volvoclub.org.uk/faq/ElectricalDensoRebuild.htm
And a discussion thread on Servicing a Denso Alternator:
https://forums.turbobricks.com/showthread.php?t=349853




2 4 0    A L T E R N A T O R    M O D    P A G E
INTRODUCTION OF THE MECHMAN ALTERNATOR
2010 Installation
In 2010 I decided that the 100 amp Volvo Bosch alternator was no longer going to cut it.  The biggest problem was how it charged at idle. When running the air conditioning (with a big electric primary puller fan and dual condenser fans), voltage was suffering badly at idle and much worse after the alternator started getting HOT. I had begun using a big Ford puller fan, starting with a Ford T-bird fan and eventually settling on a Lincoln Mark VIII fan that pulls up to 40 amps at full speed.
More on this big fan setup can be found in my
Electric Fan Page HERE.

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! 
Also this situation was forcing me to set the idle speed higher than it normally should be to help keep voltage from going through the floor.
Here's an IDLE SPEED temperature reading from my exhaust manifold a short distance from my alternator.

WHY DOES CHARGING VOLTAGE DROP SO MUCH
WHEN AN ALTERNATOR GETS HOT?

You've noticed how much voltage drops when your alternator gets hot, right? This is not something that car alternator manufacturers want to talk about.  The reason is that automotive alternators are specifically engineered so that they reduce output when they get hot.  This is because heat is an enemy to an alternator and it can be a common reason for failure.  So alternator engineers designed their alternators to have the best chances of surviving the WARRANTY PERIOD.  Engineering them to reduce output when they get hot is the answer to that. So there's really not much else you can do with a standard automotive alternator if it's getting hot and dropping voltage. Volvo did add a thin heat shield for the 240 Turbo.  It probably helped a little. This is not as big a problem in cars where the alternator is on the opposite side from the exhaust or turbo, like in the Volvo 740 or 940.



In 2010 I was introduced to Mechman high performance alternators by a Turbobricks member.  I then talked with Mechman and I was assured that the custom unit I was buying would improve voltage at idle. Mechman didn't have a Volvo alternator on the shelf, so they custom tailored a GM Delco style alternator to fit the Volvo.
Skipping ahead: The Mechman alternator did improve charging at idle and overall output was much better, but it STILL suffered from a 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.
 
I began thinking there might NEVER be a real solution for a 240 Turbo with the alternator on the 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.

I did this first custom Mechman alternator installation in 2010. 
I began a discussion thread in Turbobricks back when I did this, which helped me solve some issues. 
That thread is here:
https://forums.turbobricks.com/showthread.php?t=215613.


UPDATE NOTE: In August 2019 I learned that Mechman no longer offers CUSTOM FIT alternators like this one below, which was customized (machined) to fit a Volvo red block.
BUT, there are solutions to make a universal high-output alternator fit your Volvo.
I have added info that I hope helps. CLICK HERE.
<<< Here's the Mechman alternator compared to the Bosch 100 amp. It uses a large case GM Delco style housing that has been set up to correctly fit in the factory Volvo mounting location (while using a few spacers). I was told this Mechman was a one-off 170 amp unit based on the Delco AD230 (1996-2013 GM truck) with a little custom machining to its case so it would bolt up similar to the Volvo Bosch alternator.  More about the modifications they did can be found HERE.



<<< Here's the above Mechman unit installed.

The belt size I used for the Bosch 100a unit was 10 x 925 mm or 10 x 950 mm
I found that I could swing this Mechman slightly further from the engine and the
new belt size used was 10 x 965 mm.


<<< Attaching a ground was a bit different on this alternator.  It didn't come with a ground stud on its case, so the best solution (also suggested by Mechman) was pinching a ring terminal against the case underneath as shown here. It's a good solution as long as that 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 alternator came after I added a dedicated 4 gauge ground cable and positive cable from the alternator directly to the battery.  You can see the results of numerous tests in the above mentioned installation threadI still experienced a significant cold-to-hot voltage drop using this alternator, but it was the best result so far for any alternator I had tried.  


<<< WARNING: Don't use one of these inexpensive disconnect devices on your battery when using a high output alternator like this.  I had one of these disconnect devices on my negative battery terminal.  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 the disconnect knob was creating resistance in the ground cable circuit and the Mechman was sensitive to it.  I tossed it in the trash and made sure my battery ground was more solidly connected.




2 4 0    A L T E R N A T O R    M O D    P A G E
Unintended Side Effects of a High-Performance Alternator:
D E A L I N G   W I T H   B E L T   S L I P
<<< Back to this photo:  Have a  good look at the belts wrapping around that pulley.  There's just a little more than 90 degrees of belt wrap and the actual belt-to-pulley contact patch is small.
This was really not a problem back when the weaker Bosch alternator was in there, but it began to become more of a problem with a high output alternator. 
I found that I needed to tighten the alternator belts much more when adjusting.  Putting too much pressure on these belts can cause problems.  That bolt in the block for the adjusting bracket has been known to break off (it happened to ME) and I have seen a few people with broken water pump pulleys (see thread here: https://www.forums.turbobricks.com/showthread.php?t=323223). Over-tightening can also prematurely wear of your water pump bearings and generally your belts don't last as long as they should. They just wear faster and then they will begin slipping again sooner.
MORE ON THIS ISSUE BELOW.



2 4 0    A L T E R N A T O R    M O D    P A G E
Belt Failure Concerns
More reasons why over-tightening is BAD
<<< This is a 240 crank to AC belt.  It failed in my 242 after about 300 miles of use because I had adjusted it too tight.  The belt didn't actually break.


That long corded string stuff 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 pulley 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 becomes more like a big, soft, stretchy rubber band. 




Update 2019:
Got a NEW Bigger/Better Mechman
UPDATE NOTE: In August 2019 I learned that Mechman no longer offers CUSTOM FIT alternators like this one below, which was customized (machined) to fit a Volvo red block.
BUT, there are solutions to make a universal high-output alternator fit your Volvo.
I have added info that I hope helps. CLICK HERE.
<<< 1n 2019 I installed a new Mechman for the 242.  It's actually physically about the same size as the previous Mechman, but it's much "beefier" on the INSIDE. This is a 170 amp 6 phase HAIRPIN STATOR alternator.  According to the literature below, it's based on a GM Delco CS130D 1998-2002 GM F-body (Camaro). The Mechman part number was B8206170M.

This alternator was then custom prepared by Mechman. They had done some minor machining to the case so it would bolt up in the Volvo red block mount similar to a normal Volvo alternator.  It also got a double V-belt pulley.
More on the custom modifications that were done can be found 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 like this with a hairpin stator.

I wish someone had educated ME about hairpin stators BEFORE I BOUGHT THAT LAST MECHMAN!
There's info below that will show you how different a 6 phase hairpin stator looks compared to a normal type.

  So, the hairpin design looks pretty and it looks like it means business,
but does it actually perform better? 
Keep reading.





MECHMAN 6 PHASE PERFORMANCE
6 Phase Explanation
by Matthew Young, Mechman

A standard alternator is generally 3 phase. This means that there are three “legs” of the stator that fire in succession as the alternator spins, A-B-C-A-B-C-A-B-C producing alternating current.


6 phase alternators have two 3 phase stators inside the alternator that are slightly out of phase of one another. The two stators fire in succession like this: A-a-B-b-C-c (the second stator is in lower case). Because they are slightly out of phase with one another, there is a cancellation of electromagnetic harmonics that makes the alternator run more smoothly and more efficiently. This allows for cooler operation, more output from a smaller overall housing, and MUCH better durability.

A rectifier turns the AC current coming out of the stator into DC current. DC current is what is used in an automobile. By passing trough the diodes, half of the AC current is burned off in the form of heat as it is “rectified” into DC current. That heat is what eventually kills alternators. By having TWO rectifier plates, there is much more surface area to dissipate the heat. This is especially important in a high output alternator; as the more amperage the alternator makes, the more heat is generated. Also, by having 12 or 16 diodes (depending on which 6 phase alternator you are talking about) instead of just 6 or 8 diodes in a 3 phase alternator, the heat and electrical load can be distributed more evenly throughout the rear of the alternator housing.


<<< Here are the dyno specs for my new 6 phase alternator, Mechman PN B8206170M.  As you can see it puts out up to 145 amps at idle. 
That sounds impressive but what does that really mean in real life?

It means THIS:  Now, when I first fire the car up cold, the voltage output is 14.8 volts (stable at idle and any RPM). As things warm up, it slowly settles to about 14.7 volts. So then if I start turning on accessories, like EVERYTHING you can think of: AC and high wattage headlights, etc. (and I have 400 watts of lights), guess what.  It STAYS STABLE AT 14.7 volts!  Even when really HOT and at IDLE!

Remember this thing sits pretty close to the turbo, right? 
Still 14.7 volts!  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.


I made a couple short videos.

This one below shows the cold start voltage for this alternator: https://www.youtube.com/watch?v=YPIoiIaRiFc



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



Mechman 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 also has options for adjustable voltage if you need that. I found that it was NOT needed for my installation.
If you're interested in Mechman alternators, you can find them at:
https://www.mechman.com/





2 4 0    A L T E R N A T O R    M O D    P A G E
Up next:  
Seriously Dealing with the BELT SLIP.
ALTERNATOR IDLER BRACKET PROJECT
I began a discussion thread on this project in 2019: https://forums.turbobricks.com/showthread.php?t=350085

CHIEF SYMPTOM:
The 240 alternator design doesn't offer enough BELT WRAP (or belt to pulley contact) for an alternator that can push a heavy load.  Volvo engineers added a second belt to the 240, which makes it better, but when you exceed the grip capacity for those belts, it's just going to slip.




<<< Photo of my B21FT Engine 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, which uses a big Lincoln Mark VIII puller fan and dual condenser pusher fans.

Keep in mind that this awesome alternator holds voltage at 14.7 volts, even under a heavy load.  No other alternator I have ever tried could do that.  The others would just reduce output instead.
An alternator that simply drops voltage or reduces output might not need more belt grip.




So my hair-brained idea was to design an IDLER PULLEY (back-side idler) to significantly increase belt wrap around that alternator pulley. 


A back-side idler is NOT normally done with V-belts. Some people will tell you you shouldn't try it.  The main concern seems to be the potential for accelerated belt wear.  Well I already have that with a slipping alternator pulley. Plus so far all of these concerns appear to be based on opinion, not actual experience. 
So if this concerns you, wait and see how this turns out.
Observations and Rationalization: 
There wasn't initially enough room between the crank pulley and alternator for an idler pulley unless the alternator was moved over first. 


A bracket that could also include a mounting point for the upper adjuster bracket would eliminate the need for a new longer custom upper adjuster bracket.

After a careful look, I could see there was actually decent room in my 240 to move the alternator over a few inches.  Nothing seemed to interfere.



2 4 0    A L T E R N A T O R    M O D    P A G E
WHAT ABOUT A SERPENTINE?
This kind of thing below has been suggested.

So let's pause for a minute and I'll explain
why I DID NOT move toward 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 alternator, water pump, power steering and AC using actual RED BLOCK accessories or with a PROPER TENSIONER PULLEY, which is highly recommended.
Sure, you can cobble together some pulley parts from other cars and adapt them, but you will still need a custom crank pulley, or for a B230 you'll need a custom B230 crank dampener (???).  And you will STILL have to make all of the needed bracketry to hold all those idler pulleys and tensioner. 
In the end, will you actually get better belt-wrap on the alternator than I can with my crazy idea?



This has also been suggested:
"Why don't I just give up and change to a 740/940 style alternator mounting?"
There's nothing really 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 and changes to the alternator cable/wires.  The only question I have is about potential belt slip.  Yes, this arrangement offers more belt-wrap on the alternator pulley, but it allows for only ONE belt.
Would that ONE BELT be enough for a high output alternator like mine?



2 4 0    A L T E R N A T O R    M O D    P A G E
P R O T O T Y P E
I D L E R    B R A C K E T    D E S I G N

<<< Test Engine #1 B230: For those who don't have a 240 close by to look at, here's a view of the STOCK alternator pulley belt wrap situation.

Of course the alternator pulley slips.  Why wouldn't it? 
The belt wrap is bad.


  <<< Test Engine #1 B230: So I began playing with a bracket design to hold the idler pulley.  I started with making a prototype out of cardboard (not pictured).  Then I transferred that info to plastic to make the pictured model.  This is PVC plastic I bought from McMaster Carr.  It's easy to cut or grind and can be bent with some heat.  This material made it easy to make adjustments as I test fitted over and over and over on a B230 I had on a stand. The plastic bracket was pretty rigid and easily strong enough to mount an alternator and try out the belts.


<<< Test Engine #1 B230: Here's the plastic prototype bracket mounted on my B230 engine with an idler pulley.  Moving the alternator about 1.5 inches away from the engine did not seem to be a problem in my 240. There was plenty of room. And the nice side-effect is there's a lot more room for the oil pressure sender.


With regard to moving the alternator away from the engine, there is a possibility of interference with original steel oil cooler pipes if your car has them.  I think interference can be avoided.
My 242 lost those pipes years ago when I changed to a remote oil filter and RX7 oil cooler.
 


<<< Test Engine #1 B230: I wanted this new bracket to be able to use the stock top adjuster bracket if needed, so I added a mounting ear for that.


<<< Then 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 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 block when using a stock bracket.  The mounting holes in the block are about 15-16 mm deep and your original bolts use most of that thread depth. The stock aluminum 240 alternator bracket is 15 mm thick and your stock bolts are most likely M8 x 1.25 x 30 mm long.  The 30 mm length is measured not counting the head in case you're curious.

Keep this info in mind when deciding how long of a bolt you'll need if you add an idler pulley bracket and spacers.  In my case the spacers were 1.5 inches long and the idler pulley bracket is 0.25 inch thick, with a combined total of 1.75 inch (44 mm).  So if you used the same size spacers, you would be using bolts with a length of about 75 mm (not counting the head).


<<< Test Engine B230 #1: Here's the first test-fitting of the new steel prototype bracket.
You may have noticed that I changed to a different idler pulley in this photo.  There's more info below on this change.


<<< Test Engine B230 #1: A view of the back-side and mounting ear for the top adjuster bracket.




CHOOSING AN IDLER PULLEY
<<< This is the first idler pulley shown in the above pics.  I chose it mainly because I wanted to use a flat pulley with side flanges.  It was not expensive. HOWEVER, I had some concerns about the durability of a pulley that was originally intended for a lawn tractor.  I could not find any specs other than what I have listed here, so I have no real reason for having reservations, except that it might not be designed for a car engine.  So after thinking it over, I decided instead to choose an idler pulley that was probably actually designed for automotive use at high auto engine RPMs, temperatures, etc.


DUAL BEARING PULLEY
<<<
I found this one listed in the Dayco Pulley Guide (PDF link below). So I ordered one.

Dayco offers a good variety of pulleys and the below guide lists a lot of them, but relatively few are FLAT pulleys with side flanges.  And even fewer are WIDE ENOUGH for TWO V-BELTS (it should be more than 1 inch (26 mm) wide). 

The majority of the pulleys that Dayco offers are grooved pulleys, which are designed for serpentine belt systems. 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). I preferred a 10 mm center hole.  It's a good size for a standard sized 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 really would try that.  

Some people have expressed doubts about using a pulley with raised grooves. There was a concern about the back-sides of v-belts running on a grooved surface.  After testing for over 5,000 miles, my conclusion is it worked GREAT.  More details below.


Dayco Pulley Guide: http://www.daycoproducts.com/stuff/contentmgr/files/17/f63f2a9acd46a2fa5140ade7b2423f73/files/dimensional_pulley_guide.pdf



<<< Prototype fitted to Test Engine B230 #1: After initial testing, I decided to make an adjustment to the position 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. Long term testing was done on this configuration.

After installing this, I tested the slip resistance by putting socket wrenches on the crank bolt and on the alternator pulley nut and I applied torque.  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 has slightly MORE GRIP than the crank pulley. This is a big change!


Prototype Bracket Installed for Long-Term Road Testing on Test Engine #2 B21FT:
I installed the bracket in my 240 Turbo for long-term road testing and I put thousands of miles on it with no problems.

VERDICT: This idler has completely SOLVED all belt slip problems. 




WHAT ARE THE EFFECTS OF USING A
GROOVED IDLER PULLEY?

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

The only effect that has been caused by the grooved pulley is found in this photo.  The grooves etched some lines onto the backs of the belts.  This began to appear after only a few miles and after well over 5,000 miles it did not change
. It may look less than ideal, but it did not become a problem.  Changing to a SMOOTH pulley would probably make this go away. I'll be trying one out below.


<<< ALTERNATE BELT TEST (B230 engine pictured): I don't think the lines above made by the grooved pulley will be a problem, but if it becomes unwanted, a switch to this type of belt would probably make it a non-issue.  I bought a set of the belts shown here, but I have not used them yet. 
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 (left side belt in BELOW photo).  This 11 mm width will fit the 10 mm wide pulleys in a 240 just fine.





KEVLAR BELTS
I Found this info while searching, so I thought I would add it here in case it becomes useful to anyone: 
Kevlar / Aramid belts
are created to be stronger than standard v-belts. In a Kevlar belt, the normal polyester cords are replaced with the much stronger Kevlar cords. When using machinery with a back side idler, the belt takes a beating and normal belts can wear out faster. Kevlar drive belts are made to last longer in these situations.
https://www.vbeltsupply.com/kevlar-corded/3lk


SMOOTH SURFACE PULLEY
<<<
So after about over 5,000 miles of very successful testing I decided I would try out a smooth pulley to see how things went. As expected, the smooth pulley did not mark the belts.  No issues.






This pulley only comes with a 17 mm center bore.  I have designed this bracket to use a smaller bolt, 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 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 for me though. I just tapped it in with a hammer.
 
Cost was very small for the bushing:
https://www.amazon.com/gp/product/B00AZ0OPPQ/
   


<<< So while the above smooth pulley works fine, I still have a preference for the DUAL BEARING pulley that I started with (DAYCO 89516).  So I decided to modify it.

I used my bench grinder to slowly grind down the raised grooves while the pulley slowly spun on a bolt. So basically I turned this into a smoother pulley. It only took a few minutes.



2 4 0    A L T E R N A T O R    M O D    P A G E
INSTALLATION GUIDE FOR
IDLER PULLEY BRACKET
As you can see here, the new final design for this bracket has been made for a wide range of adjustments for different size alternators, different sized idler pulleys, different positions for the top adjuster bracket, etc. 
The below setup was installed into my 240 Turbo B21FT. 
I spaced the idler pulley on the bracket using a couple washers and it has about 1/8 inch clearance from the bracket.
IMPORTANT:  Be sure to use lock-nuts.  Normal fasteners can vibrate loose over time and that would not be good.
       


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 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 your bolts are close to being too long, you can always add a washer.




HARDWARE: I used 1.5 inch long steel spacers and 75 mm long bolts (M8 x 1.25 x 75) bolts with washers (pictured below).  These bolts pictured are strong Grade 10.  I recommend Grade 10 because of the long length.  If 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 a few different dis-assemblies and re-assemblies. Not a problem.

If you decide on a different length spacer, then you should adjust your bolt length.


The belts I used for this final installation were Gates Metric-Power XPZ 1120, 1120 mm length, 10 mm wide. They have a cog on the bottom. Gates matches belt length so when ordering these in pairs, you will get matching belts.  This seems like a no-brainer, but MOST belt manufacturers DO NOT offer this and I have had frustrating problems before.
https://www.amazon.com/Gates-XPZ1120-Metric-Power-V-Belt-Section/dp/B00CJJJU2O
 


Below left photo: With the alternator removed and out of the way, I positioned the bracket over the mounting holes and inserted a SHORT original bolt into one of the holes.  This was to hold the bracket in place so it wouldn't fall and knock me on the head.  Plus it helps a lot when you're inserting the alternator bracket, spacers and long bolts one-by-one and you have only two hands.  You can remove that short bolt after getting one of the long bolts started.

Before tightening the bolts, pay close attention to the alignment of the idler pulley. It needs to be lined up and pretty close to being CENTERED on the two back rows of the crank pulley. Also the idler pulley should be plumb, or straight vertically.  If you have a short bubble level you can compare the vertical angle of the crank pulley with your set angle of the idler pulley.  Try to make them the same. 
 
Proper V-Belt Tension
Most DIY Volvo owners don't have special belt tension tools.  So my best technique for setting belt tension is the same 90 degree flex method that is demonstrated in the below serpentine belt video.
https://www.youtube.com/watch?v=FMiB3CnZpRc





2 4 0    A L T E R N A T O R    M O D    P A G E
FITTING A UNIVERSAL HIGH-PERFORMANCE ALTERNATOR
JUST SOME RAMBLING THOUGHTS THAT SHOULD HELP.
In August 2019 I learned that Mechman no longer offers custom alternators to fit a Volvo red block. They do, however still offer a wide variety of alternators, but they just don't want to deal with customizing them for a Volvo as you can read about below.


When searching for an alternator, you should look for something with mounting points similar to the original Bosch.  In other words, choose something similar to the below left image as opposed to the below right image.


Keep in mind that the Mechman alternator below on the left (which I installed in 2010) was NOT originally designed to fit a Volvo.  This particular alternator was chosen by Mechman because the mounting points were somewhat close to the Bosch mounting points.  Not precisely close.  Just somewhat close.  After working out the below information, it's my conclusion that there are lots of alternators to choose from which will be a close fit.


The Mechman pictured below is believed to have originally begun as a Delco AD230 for a 1996-2013 GM truck.
The Mechman I installed in 2019 (click here) was originally designed as a Delco CS130D for a 1998-2002 GM F-body car (Camaro). 
So If you buy a Mechman alternator or a high-performance alternator from another company, you can use this information below as a guide to help you find a model that will fit. 
Or just choose something that's made for a 1996-2013 GM truck  or a 1998-2002 GM F-body car (Camaro) and know it can fit.
And remember that I recommend a 6 Phase Hairpin Stator alternator.

Lets discuss the above dimensions. 
Dimension A is the mounting flange for the Volvo alternator bracket, which uses rubber bushings and a long 8 mm bolt.  The Bosch alternator fits just right in that bracket, but as you can see the Mechman dimension is 3/4 inch smaller.  A spacer (or 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 Mechman originally began with this flange being 2 inches thick (Dimension D)Mechman had the case custom machined so this flange was reduced to 1.25 inches thick.  That reduction brought it CLOSE to the same as the Bosch (which is 1 inch thick). This modification worked fine, but as I recall I did make an adjustment 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 to make the alignment better. Ultimately it worked just fine.

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


So . . .  if you choose an alternator which has a thicker Dimension B (such as a Delco truck or Camaro alternator mentioned above), you COULD disassemble it and have the case machined like Mechman did if you like. 
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. 
The second and third image below shows the top adjuster bracket mounted in the normal location for an alternator with dimensions similar to the Bosch.
   


Now have a look at this change below. . . .  If needed, it's possible to mount the top adjuster bracket to the back-side of the idler pulley bracket as shown BELOW. As you can see, I have demonstrated this by inserting a spacer to simulate an alternator flange (Dimension B) with a full thickness of 2 inches, like it was before Mechman had it modified. So just like that, new possibilities emerge for an unmodified Delco alternator.

   


V-BELT PULLEY
When choosing an alternator that you think is reasonably close, the next important thing to consider 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 proper 240 double V-belt pulley is made to fit 10 mm wide belts (same for the crank and water pump pulleys). 
The below photo shows three double V-belt alternator pulleys. The left pulley is for a Bosch (Volvo) using 10 mm wide V-belts. The middle pulley is for a Delco using 10 mm V-belts.  The right pulley is for Delco using 13 mm wide V-belts. The difference does not look large in the photo, but it could make a difference if you try to use a 13 mm pulley for 10 mm belts.



CUSTOMIZING A V-BELT PULLEY

Here's an issue that I needed to deal with when I installed the latest Mechman in 2019. I'm posting this just to show that sometimes unexpected problems come along and can be solved pretty easily.
The above middle 10 mm pulley was originally supplied by Mechman with the first Mechman alternator I bought back in 2010 (
Delco AD230 for a 1996-2013 GM truck). The pulley worked with no issues on that first Mechman.  The part number for this pulley is 24-1101 (or 241101) in case you need it. 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 generally characterized by the 13 mm dimension from the flange to the center of the first groove.

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

The first thing I did was try to fit the above middle 10 mm pulley on the new Mechman. It did actually go on (same 17 mm shaft diameter), however the shaft length on the new alternator was different (shorter) and that made it impossible to use the pulley.  The shorter alternator shaft meant the 16.5 mm flange dimension in the below diagram was a bit too thick and the large nut holding the pulley could not be threaded on fully.

The solution I chose was having a 24-1101 pulley custom machined, cutting the recess deeper to reduce the
16.5 mm flange thickness to 12 mm. That solved the problem.
The diagram below shows the factory dimensions of the 24-1101 pulley.
 


Here's a possible alternate 2-groove pulley for 10 mm belts that I found later, but have NOT tried.  It has a larger diameter, but it might have been worth trying had I found it before having the above pulley modified. I think it would have needed only a couple 17 mm washers to get the proper spacing.
This is PN 24-3105 (or 243105).
Chrysler PN 5227174 for Chrysler 40/90, 50/120A alternators. Chrysler, Dodge, Plymouth 1987-1989.






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