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
IDLER PULLEY


      UPDATED: October 16, 2024        CONTACT    
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Alternator Idler Pulley Bracket Fixing BELT SLIP
Why not a
SERPENTINE BELT?
Alternator IDLER PULLEY
Project Details HERE

Broken BOLT in block

For more 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. 
IN STOCK
240 Steel Idler Pulley Bracket with
black powder coat.  Price: $129.00
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AVAILABLE FOR PURCHASE WITH ABOVE BRACKET.
Grade 10 Bolts Set (3 pieces): M8 x 1.25 x 75 mm long, high strength Grade 10. Set of 3. Washers included. $5.00

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AVAILABLE FOR PURCHASE WITH ABOVE BRACKET.
Steel Spacers Set (3 pieces): 1.5 inches long. Seamless steel. $10.00

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I began this project in 2019. 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 over 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!



Why is there BELT SLIP
Incurable Belt Slip during High Load.
The 240 original alternator design doesn't offer enough BELT WRAP (belt to pulley contact) for an alternator that can pull 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 capability for those belts, it's just going to slip. Adding a higher amp alternator make this problem worse.
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.
 
 
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. 

COMMON 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: 
turbobricks.com/b21-b230.323223/.
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.



  It was time to seriously deal with the
BELT SLIP PROBLEM
After installing my new Mechman alternator in 2019 (The Mechman is in the photo below right) I found I needed more belt grip. This was an immediate problem when running the AC and cooling fans.
This is the reason for developing this
ALTERNATOR IDLER PULLEY PROJECT.

Photo below showing how a 240 ALTERNATOR looks with stock POOR BELT WRAP:
 
So my idea to FIX BELT SLIP was to design an IDLER PULLEY (technically a back-side idler pulley). My goal was to significantly increase belt wrap on the 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. I probably had faster water pump wear too. 
And so far all of these negative "concerns" appeared to be based on opinion, not actual experience. Other than for industrial machines, I have not found ANYONE who has attempted this. 
So if this concerns you, wait and see how this turns out.


Here's my original concept introducing 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 BELT 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, but it's an interesting project.  This guy made a 7 part video project on all the work he did to get all these accessories to work using one serpentine. 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.
"
A single V-belt  or 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 like the 740 really be good enough for a high output alternator? 
 
I think NOT.  Some cars may be different, but I can tell you that I have tried just one belt with my idler pulley setup. 
Even with really good belt wrap I've found ONE BELT will NOT BE ENOUGH with an alternator as strong as mine. I discovered this when I had a mismatched pair and only one of the belts had full grip.



PROTOTYPE BRACKET TESTING BEGINS
INITIAL IDLER BRACKET DESIGN
   
Test Engine 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 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 BELOW) .   

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 up to 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 range of movement for belt installation or adjustments. And a very 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 his 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's 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 Test Engine B230:
 
I wanted this new bracket to be able to use the factory 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 the 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 prototype steel bracket made.
STEEL PROTOTYPE BRACKET #1:


 
I had this 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 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.
  In my case the spacers used 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).
Bolt length will be different if you use spacers with a different length.

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


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

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 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 first 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 durable enough 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 info about 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. Some have side flanges, which I liked.  And even fewer are WIDE ENOUGH for TWO V-BELTS (I think it should be well over 1 inch (26 mm) wide). This one is 30 mm wide. 

The majority of the pulleys that Dayco offers are grooved pulleys, which are designed for a grooved or ribbed 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. 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 a SINGLE 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 choose that.  

I had 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.  So I tested this using Gates belts for over 5,000 miles, my conclusion is it worked OK, but it WILL eventually cause some wear damage to the beltMore details and photos below CLICK HERE.
MY CONCLUSION:  Grooves should be avoided. More below.
Dayco Pulley Guide PDF: daycoaftermarket.com/PULLEY-DIMGUIDE.pdf
Dayco Main Page: https://na.daycoaftermarket.com/en/


A WIDER DUAL BEARING PULLEY is available.

I have not tried this one. If I did try this, 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 choose this pulley and still want to use an 8 mm bolt in the center, you would need to buy some center bushings which can be tapped into the holes to reduce it to 10 mm. More about these 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 beltMore details and photos below CLICK HERE.
CONCLUSION:  Grooves should be avoided.

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


Steel Prototype MODIFIED and fitted to Test Engine B230:

After initial testing, I decided to make an adjustment to the position or height of the idler pulley. 
I ra
ised 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.
After this, I then did long term testing (more than 5000 miles) with this configuration in my 240.


Here's the modified steel prototype bracket installed for long-term road testing in my 240 with 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.
If this bracket looks a little different, YES, this prototype was modified before settling on this configuration.
  
Belts in this photo: GATES METRIC-POWER XPZ 1120
These are 1120 mm in length, 10 mm wide. They have a cog on the bottom.
VERDICT:
This idler
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.
 HOWEVER, since I think the grooves will eventually cause more damage, I don't recommended using a grooved pulley.
  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 other belts.
DIFFERENT BELTS (B230 test engine pictured).

  I bought a set of the belts shown here to test as an alternative. 

USING the STEEL PROTOTYPE BRACKE
T

 
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 little 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 PAIRI 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 belt 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 unless you want to drill out a hole and use a 17 mm 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 (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 a Mechman PN B8206240B, which is an all black GM version with 240 amps.



Installation Guide
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 early style TENSION ADJUSTER BRACKET.  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 to about 1984.  The bracket is always mounted behind the alternator mounting ear. This is the same as bracket #3 in the bracket assortment photo below. Volvo PN 1276128.

This later tension adjuster bracket below has a tension adjusting bolt. This type of bracket was found in B230F equipped 240s beginning in 1985.  This is bracket #4 in the bracket assortment photo below. It's Volvo PN 1346365.  It appears that the Volvo diagram below is INCORRECTLY showing this bracket installed BEHIND the alternator mounting ear.  The correct factory way is shown in the photo below showing it in FRONT of the alternator.
  
At least one person using my idler pulley bracket has used a LATER style tensioner mounted BEHIND the alternator.  You can see a photo HERE.
I have NOT yet personally tried fitting one of these later style brackets in my car or in my tests. If you have used this with one of my idler brackets, please let me know the details.



Here's a photo BELOW 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 (1985 and later 240).
Source: turbobricks.com/1981-245-alternator-adjuster.356867/




LATER BRACKET UPDATE: I have acquired the below style tension bracket and when I have some time I'll be experimenting with it to see how well it fits my alternator with the idler pulley bracket.  I think it should do ok.
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. 
This is Volvo PN 1346024 acquired from iPd.


The PULLEY I ultimately continued using is Dayco 89516.  I chose this one because it has dual bearings and fits perfectly.  I don't think dual bearings is a requirement, 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 Dayco 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 this one 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/

BOLTS
The bolts I used below were M8 thread
(M8 x 1.25) that I pulled from my spare bolt bin. I think the length of that pulley bolt BELOW is about 50 mm. The length of this bolt won't be standard, because there are a few different pulleys you could choose from. I spaced the pulley away from the bracket using a couple washers and it has about 1/8 inch clearance or less from the bracket.
IMPORTANT:  I strongly recommend using LOCKING NUTS here.  Normal fasteners can vibrate loose over time and that would not be good. And if one of these vibrates loose, accessing it without disassembly will be pretty hard. So use a lock nut and it'll treat to nicely.  There are many choices for a good lock-nut. If you're using M8 bolts like this, the lock-nuts pictured below are these from iPd: https://www.ipdusa.com/products/11455/.
       

ENGINE BLOCK THREAD DEPTH
I checked both my B230 and my B21 engine blocks to see how deep the threads are for the three alternator bracket bolts.  Both blocks had holes that were about 15 -16 mm deep. I measured by smearing a little grease on the end of a new bolt (BELOW PHOTO) and threading it all the way in until it reached bottom. Keep this thread depth question in mind during your installation.

In my opinion, you should try to get at least 10 mm of bolt thread inserted into the block during your installation. Just be sure your bolts are not be so long that they bottom out before becoming tight. If a bolt length 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) with M8 washers (as pictured below).  NOTE: 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 offered here.

But if you use your own bolts and you only have Grade 8 bolts, the
y 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.

SHORTER SPACERS:
BELOW PHOTO:
I received some feedback from a customer who used shorter spacers: 1 1/8 inch spacers instead of 1 1/2 inch.  He wanted to add a little more clearance to some 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 I used, then you should change your bolt length.



OPTIONS FOR PULLEY AND TENSION ARM HOLE POSITIONS
I designed the final version of this bracket to have many options for the mounting locations for the pulley and tension arm.
The current positions that I use for my 240 are:  Pulley Hole #2 and Tension Arm Hole A. 


These images BELOW 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 below).
   

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 seem to 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). 
GETTING MATCHED BELTS.
Keep in mind that these should be matched in length and width. Some places might 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 if you think it's needed, 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 after I got a set that were not matched.
www.summitracing.com/15440

Alternate Belts: DAYCO 15435 43.5 inch (1105 mm)
Web B. told me he used the Dayco 15435 1105 mnm belts when he installed this idler bracket. A shorter belt like this will swing the alternator a little closer toward the engine. It's possible that you'll lose some room to push the alternator close to the engine when you're installing these belts.  It could make installation a little harder.


.
INSTALLING, POSITIONING, AND ALIGNING THE NEW BRACKET

BELOW left photo: Working from under the car . . . With the alternator and original bracket removed and out of the way, I first position the new pulley bracket against the engine block over the mounting holes. I loosely thread 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 me on the head when I let it go.  Plus it helps a lot when I'm inserting the stock alternator bracket, spacers and longer bolts one-by-one while I have only two hands.  You can then remove that short original bolt after getting one of the long bolts started through the factory bracket and spacer and into the block.
 

PULLEY 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 to 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 yet. Then the final step is pushing the alternator against the engine and then push the belt over the idler pulley. Then I do the same for the second belt.
 
 
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 below.
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 USING AN EARLY TENSION BRACKET
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.
 



Can this bracket be used to eliminate the problem of a BROKEN BOLT in the block?
YES it can.

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. His use of this bracket was a little different than usual, but if experimentation works, I'm all for it.



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 is 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 (at 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. And if you're really observant, you'll notice Tyler placed the spacers between the block and the idler bracket, instead of between the idler bracket and factory alternator bracket.  If it works, it works. It offers more possibilities.



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