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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
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.
regulator successfully increased my beginning (COLD) voltage from 13.8
volts to 14.4 volts. But the adjustable regulator could not increase amperage capability for 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 HOT voltage output could drop by more than ONE VOLT!
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.
CAN COOLING DUCTS BE INSTALLED IN A VOLVO 240?
Yes, I guess if you're determined enough. There isn't any room behind this 240 alternator below for a shroud or duct, so it would require some work.
But if that oil filter is re-located, there may be room for something like this cooling shroud below.
This shroud is Porsche PN 96410640302.
Volvo (Bosch) 55 Amp versus 100 Amp
Alternator Size Comparison
Here's the bigger 100 amp Bosch alternator
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 the 1990s. I simply wanted
something bigger than what I had, since in
I was using up the capacity of the
original 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
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
I put this info together many, many years ago for my
own 240 uses. I thought I would share it here.
10 x 925 mm
2 needed. 1976-83 240. Also PN
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 belt as a pair: 973537.
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
13 x 1075 mm
1977-84 240. Also 12.5 x 1075 mm.
AC to PS
10 x 850 mm
AC to PS
11.9 x 835 mm
Crank to PS (no AC present)
10 x 938 mm
Crank to AC
13 x 925 mm
1976-84 240. Also PN 978678.
Crank to AC
13 x 975 mm
Crank to AC
13 x 938 mm
<<< 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 a 240 Turbo. That
brass 45 degree fitting came standard on a 240 Turbo, but there the
bigger alternator still hit the sender with that fitting.
<<< So generally the oil pressure sender needs to be re-positioned to make
room. Sometimes finding the room for it need some new ideas, 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 dealt with the cramped space a bit differently. I mounted a remote sender after I have some bad experiences with other options This option 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 ANY BRASS ELBOW, but this would require some planning to get the alternator EVEN 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 below it. 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.
What about a DENSO?
Here's the Nippon Denso alternator in a 240. It has become popular to install this smaller casealternator 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 theoil pressure sender with this more compact alternator.
Denso alternators found in Volvos are usually 80 Amp or 100 Amp. They
look similar, but you'll notice some 80 Amp units have a 6 mm lug for
the big red cable. 100 Amp units will have an 8 mm lug.
INCREASING 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 very 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
INTRODUCTION OF THE MECHMAN ALTERNATOR
This installation was in 2010
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 or if I turned on the air conditioning. I had begun
using a big Ford electric puller fan, starting with a Ford T-bird fan and eventually getting to a Lincoln Mark
VIII fan that pulls up to 40 amps at full speed.
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 a temperature reading from my exhaust manifold (AT IDLE) a short distance from my alternator.
WHY DOES CHARGING VOLTAGE DROP SO MUCH
WHEN AN AUTOMOTIVE ALTERNATOR GETS HOT? (SPOILER: It's about the WARRANTY) 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
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 told them about my low idle voltage. I was assured
the custom unit I was buying 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.
ahead: The 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 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 learned that Mechman no longer offers CUSTOM FIT alternators like
the one I bought below. It was customized (machined) to fit a Volvo red block. BUT, I have since found there are STILL excellent solutions to make a universal high-output alternator fit your Volvo. I've added info that I hope helps. CLICK HERE.
Here's the Mechman alternator from 2010 compared to the Bosch 100 amp I was using. The Mechman used a large case GM Delco style housing that has been slightly modified to
fit in the factory Volvo mounting location (while also using a few spacers). I
was told this Mechman unit was a one-off 170 amp alternator 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.
Similar Volvo conversions have been done using GM AD244 and GM DR44
late model truck alternators. The reported benefit is excellent
output at idle, which is something the old Volvo Bosch unit don't do
well. More about the modifications Mechman did can be found HERE.
Here's what the above Mechman unit looked like installed in my car.
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 big ground was a bit
different on this alternator. 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 caseunderneath 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 from the alternator directly to
the battery. You can see the results of numerous tests in the
above mentioned installation thread. I still
experienced a significant COLD-to-HOT VOLTAGE DROP using this
alternator, but ultimately it was the best result so far for any alternator I had tried.
<<< WARNING NOTE: 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 high 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.
Unintended Side Effects of a High-Performance Alternator: DEALING WITH BELT SLIP
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.
was not a problem back when the weaker 55 amp 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 and then they needed adjusting
later. I was putting a LOT of stress on these belts and you'll see
below it can cause problems. That bolt in the block for the adjusting bracket has been known to break off(it also 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 is just plain BAD. It 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.
Belt Failure Concerns
More reasons why over-tightening is BAD
This is NOT an alternator belt. This is a 240crank to AC belt. It failed on my 242 after about 300 miles of use because I had adjusted it too tight. The belt didn't actually break, but it did jump off the pulleys.
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 becomes more like a big, soft, stretchy rubber band.
Update 2019: I Got a New BIGGER/BETTER Mechman
UPDATE NOTE: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 excellent solutions to make a universal high-output alternator fit your Volvo. I have added info that I hope helps. CLICK HERE.
In 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 alternator came with a 170 amp 6 phase HAIRPIN STATOR.
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.
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?
6 PHASE HAIRPIN PERFORMANCE
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. As things warm up, it slowly settles to about 14.7 volts. So if I start turning on accessories, like EVERYTHING you can think of: like AC and high wattage headlights, etc., guess what. It STAYS STABLE AT 14.7 volts! Even when really HOT and even at IDLE!
This has never happened to me before!
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.
6-phase alternators are not cheap, but they have
very high quality. Be careful if you begin
looking at no-name or Chinese made
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.
interested in Mechman alternators, you
can find them at:https://www.mechman.com/
If by chance you're playing with GM 130D 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 later. https://www.youtube.com/watch?v=hdK8ZqNvGsc
Seriously Dealing with the
BELT SLIP ISSUE and
ALTERNATOR IDLER BRACKET PROJECT.
CHIEF SYMPTOM: Incurable Belt Slip during Load.
The 240 original 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.
I spent more time that I should have trying different belts and cranking them tighter and tighter. In the end, I STILL HAD BELT SLIP.
Photo of my B21FT Engine Alternator 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 to 12 volts or reduces output might not need more belt grip.
So my idea to FIX BELT SLIP 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 faster belt wear. Well I
already have faster belt wear with a slipping alternator pulley. And so far all of
these concerns appear to be based on opinion, not actual experience or facts.
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 to add 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 be a BONUS and eliminate the need for a new longer custom upper adjuster bracket.
It also eliminates the bolt going into the front of the block that breaks off!
After a careful look, I could see there was actually decent room in my 240 to move the alternator over a bit. Nothing seemed to interfere.
So let's proceed.
WHAT ABOUT A SERPENTINE? This kind of thing below has been considered. First, let's look at how the 850 and 960 serpentine belt was arranged. All of the accessories were designed to be on ONE side.
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 proper pulleys foran 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. And you will STILL have to make all of the needed
brackets to hold those idler pulleys and the tensioner. It can be done, but it would be VERY expensive. In the end, would you get better belt-wrap on the
alternator than with my idea?
This has also been suggested: "Why don't I just give up and change to a 740/940 style alternator mounting?" I don't think there's 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 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 good enough for a high output alternator like mine?
Maybe. Don't know for sure.
P R O T O T Y P E
IDLER BRACKET DESIGN
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-bad-bad.
Early 240 Alternator Mount Detail More original bracket (and tensioning arm) info can be found in the installation guide below.
Test Engine #1 B230: So I started with making a bracket out of cardboard (not pictured). Then I made a prototype bracket in plastic (PHOTO BELOW).
This is 1/4 inch PVC 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 when test fitting over and over on a
B230, which was on an engine stand. The 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 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 also. And the nice side-effect is there's a LOT MORE ROOM for the oil pressure sender.
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 avoided.
My 242 lost those pipes years ago when I changed to a remote oil filter and RX7 oil cooler.
Details about this can be seen in my OIL COOLER PAGE.
Again Test Engine #1 B230: I wanted this new bracket to be able to use the stock top adjuster bracket (tensioner arm).
This is why that mounting ear was added.
If you have ever had the bolt for the adjuster bracket BREAK 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.
By the way, here's a video below showing how to repair this broken bolt if this happens to you.
So 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 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 block when
using a stock bracket. The mounting holes in the block are usually about 15-16 mm deep and your original bolts use up 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 bolt 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 new 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).
AgainTest Engine B230 #1: Here's the first test-fitting of the 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 different pulley.
Again Test Engine #1 B230: Here's a view of the back-side and the mounting ear can be seen 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, since it was originally intended for a lawn
could not 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 probably actually
designed for automotive use at higher engine RPMs, temperatures, etc.
DUAL BEARING PULLEY I
found this pulley listed in the Dayco Pulley Guide (PDF link below). So I ordered one. Yes, it's a GROOVED pulley.
Dayco offers a good variety of pulleys and the below guide lists a lot of them, but relatively few areFLAT 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. The concern was about the
back-sides of v-belts running on a grooved surface. After testing
for over 5,000 miles, my conclusion is it worked really well. More
details below CLICK HERE.
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 in my 242.
NOTE: After installing this on my 242, 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 actuallyhas 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.
Yes, this bracket was modified a couple times before settling on this configuration.
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.
The only effect that has been found 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, so stay tuned. I'll be trying one out below.
ALTERNATE BELT TEST (B230 engine pictured):
don't think the lines above made by the grooved pulley will be a
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 as an alternate.
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.
After trying this, I find that I like these belts better because they have more internal reinforcement than the Gates belts.
The belt size I used is 1120 mm long, Dayco PN 15440. I ordered them through Summit Racing ($12 each). Keep in mind that you should buy belts like this as a MATCHED PAIR. Some places will send you un-matched belts if you don't ask for a matched pair. You don't want one belt longer (or
slimmer) than the other. That happened to me. So if needed, you might try to talk
to someone in-person and get them to send a matched pair. Summit Racing did this for me when I called. https://www.summitracing.com/parts/dac-15440
KEVLAR V-BELTS BELTS I
have NOT tried 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 above only comes with a 17 mm center bore.
I have designed the idler 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. I just tapped it in with a hammer.
Cost was very small for this bushing (under $10): https://www.amazon.com/gp/product/B00AZ0OPPQ/
while the above smooth pulley works fine, I still have a preference for the DUAL BEARING pulley that I used before (DAYCO 89516). 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 grinding. So basically I turned this into a much smoother pulley. It only took a few minutes. Worked perfectly.
INSTALLATION GUIDE FOR IDLER PULLEY BRACKET
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 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 ADJUSTER BRACKET (tensioner arm). A particular style is not required. 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 about 1985. This is the same as bracket #3 in the bracket assortment photo further below. Tensioner Arm Volvo PN 1276128.
This SECOND adjuster bracket (tensioner arm) 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.
Tensioner Arm Volvo PN 1346365.
The IDLER PULLEY I chose is Dayco 89516.
I chose this one because it has dual bearings and fits perfectly.
I flattened the grooves to provide a smoother surface for the backs of
the belts to ride on. More details about this pulley can be found HERE.
There is a choice of pulleys. You can also choose a pulley with a smooth surface, but it will not haveDUAL bearings. See that HERE.
bolts I used were M8 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 are these: https://www.ipdusa.com/products/11455/Copper-Flanged-Lock-Nut-CRP-11621711954-948645-124875.
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: 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 and 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.
If you decide on a different length spacer than 1.5 inches, then you should adjust your bolt length.
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.
Gates supposedly matches their belt lengths,
so when ordering these in pairs you should get matching length belts.
https://www.amazon.com/Gates-XPZ1120-Metric-Power-V-Belt-Section/dp/B00CJJJU2O Matched belts seems like a no-brainer, but some other belt manufacturers DO NOT offer
this and I have had frustrating problems before with mis-matched belt pairs.
DAYCO TOP COG 15440 1120
recently, I tried using the below Dayco Top Cog belts. I like
these belts better because they have more inner reinforcement than the above
The belts I used are 1120 mm long, Dayco PN 15440. I ordered them through Summit Racing ($12 each). 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. https://www.summitracing.com/parts/dac-15440
POSITIONING AND INSTALLING THE BRACKET
Below left photo:
With the alternator removed and out of the way, I positioned the
bracket against the engine over the mounting holes and I inserted one SHORT original bolt into one of the holes.
This is to hold the bracket in place so it doesn't fall and knock you
on the head when you let loose of it. Plus it helps a lot when you're inserting the
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 through the alternator bracket and spacer.
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
rear grooves of the crank pulley. Also the idler pulley should be
straight, or at 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 your angle of the
idler pulley. Try to make them the same.
PROPER V-BELT TENSION Most DIY Volvo owners don't have special belt tensioning tools. So my best technique for setting belt tension is the same 90 degree flex method that is demonstrated in this below serpentine belt video. https://www.youtube.com/watch?v=FMiB3CnZpRc
Or use this image below as a guide. It's from the 1984 240 7,500 mile maintenance service manual.
FITTING A UNIVERSAL HIGH-PERFORMANCE ALTERNATOR TO A 240
In August 2019 I learned that Mechman no longer offers customized
alternators to directly 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. It turns out the customizing was actually pretty minor. So it's certainly possible to still fit a great high-performance alternator.
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,
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.
they altered the aluminum case at that top 2 inch thick flange by
machining the back surface of that TOP 2 inch dimension, where the adjuster bracket attaches. This 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 it into a Volvo.
Then of course they 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 as 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 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.
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 need to make an adjustment to the 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 to make the alignment better. 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. This made no difference at all.
Is Machining an Alternator Case Really Needed? No! As mentioned above, it's NOT.
did a bunch of measurements and determined that an UNMODIFIED non-Volvo
alternator can be made to fit if the top adjuster bracket (tensioner arm) is MOVED. The
easiest method I know to do that is to install one of my idler pulley
If you choose an alternator which has that thicker Dimension B
(such as a Delco truck or Camaro alternator 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 below shows the top adjuster bracket mounted
in the NORMAL location for an alternator with dimensions similar to the
(Yes, that IS a Bosch in this photo).
Now have a look at this change below. . . .
This is a Mechman. It's possible to mount the top tension 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 at the alternator to
simulate a thicker 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 alternator is possible without a lot of fuss.
Choosing a V-BELT PULLEY
When considering an alternator that you think is reasonably close, the next important thing
to determine is if it can be fitted with a V-belt pulley.
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 size for the crank and water pump pulleys). 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.
The middle pulley is for a Delco alternator using 10 mm V-belts.
The right pulley is for a Delco alternator
13 mm wide V-belts.
The difference does not look large in the
but it could make a difference if you try to use a 13 mm pulley with 10
mm belts. It might be OK, but I prefer the correct pulley V-belt
width. However, if you decide to use a 13 mm belt pulley, let me know how
it works out.
I CUSTOMIZING A V-BELT PULLEY
Since I was a bit obsessive about a good fitting 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 this is how I solved this one.
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). This pulley worked with no issues on that Delco. 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 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, 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. 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 try to fit the above middle 10 mm 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 alternator 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.
The solution I chose was having a 24-1101 (10 mm) pulley custom
machined. This mean that I had the recess cut deeper to reduce the 16.5 mm flange thickness to 12 mm. That solved the problem. The diagram below shows the MODIFIED dimensions for this pulley.
I FOUND THIS ONE LATER Here's a possible alternate
2-groove pulley for 10 mm belts that I found later, but have NOT tried yet.
It has a slightly
larger diameter, but it would be worth trying. I think it would have needed
one or two washers behind it to get the proper spacing out, away from the alternator, since there is
no flange shoulder sticking out on the back side.
This is PN 24-3105 (or 243105). Chrysler PN 5227174 for Chrysler 40/90, 50/120A alternators. Chrysler, Dodge, Plymouth 1987-1989. If you try one of these, please let me know how it works out.