Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

[Joe R.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

It looks like Leif's C/S has three standard pulleys with no gaps between them. While James' C/S has two deep pulleys behind a standard PS add on pulley with a gap/spacer in between.

Correct?

Let's keep in mind that Leif's car is a '67. I think it is well established that for 1966-67, the C2 L79 equipped with *both* A/C and PS used a full set of standard-groove pulleys. What seems odd about this is that otherwise, the L79 got deep-groove pulleys. My theory, as described in previous posts, is that GM found that the deep-groove pulley set placed the PS pump pulley too far forward for reliable frame clearance with normal production tolerances.

What has always been confusing to me is the 1965 setup for an L79 with *both* A/C and PS, which is what the OP was describing. From this discussion, I think we have learned that for 1965, GM used a deep-groove pulley set for the first two belts (the water pump pulley grooves), but combined that with rather unique (and now rare) standard-groove pulleys for the crank add-on pulley and the PS pump pulley. The resulting stack-up on the crank had no gap between the double crank pulley and the PS add-on pulley.

The photos of James' crank pulley setup do not look like what I would expect to see. I would expect no gap between the double pulley and the add-on pulley. My guess is that on James' car, the double crank pulley is standard-groove, which makes it less wide than the corresponding deep-groove pulley on the WP. From the photos, I can not tell whether the add-on crank pulley is standard-groove or deep groove.

[Joe R.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

Thanks Joe! Very helpful.

I understand the same width belt is used in standard and deep groove pulleys. This places the top of the belt below the top of the deep groove pulley for more control at high RPM. Is this correct?

I haven't paid close attention, but I also believe the standard groove pulleys seem to be the same width. Maybe others can comment about this.

But if this is the case, why are different width belts specified? For example, I think all the pulleys on my '70 LS5 are standard groove (and the same width) yet two belt widths are specified (15/32" for WP and AC; 7/16" for alt and PS; ).

So this means the top of the 7/16" belts appear lower than the 15/32" belts (which looks a bit funny). Is this correct?

Is this because wider belts are specified for higher loads (in this case, the WP and AC have higher loads, so they use a wider belt than the alt or PS)?

Hi Mark:

I'm not sure why GM specified different belt widths for certain locations. On my '67, the A/C belt is specified to be wider than the others. My guess is that GM felt the wider belt was necessary to support the load of the A/C compressor, but that is just a guess.

[Mark E.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

I think it is well established that for 1966-67, the C2 L79 equipped with *both* A/C and PS used a full set of standard-groove pulleys. What seems odd about this is that otherwise, the L79 got deep-groove pulleys. My theory, as described in previous posts, is that GM found that the deep-groove pulley set placed the PS pump pulley too far forward for reliable frame clearance with normal production tolerances.

Is redline lower for L79s with AC, compared to L79s without AC? If yes, maybe Chevy decided deep groove pulleys are unnecessary.

[Joe R.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

Is redline lower for L79s with AC, compared to L79s without AC? If yes, maybe Chevy decided deep groove pulleys are unnecessary.

For the 1967 Corvette L79 (and I believe other C2 years as well), the redline was the same regardless of whether the car had A/C or not.

I have heard that for the C3 LT1, GM did have a problem with the A/C belt coming off, and this was responsibe for a delay in A/C being available with the LT1. My understanding is that GM "fixed" the problem by lowering the redline when the LT1 was equipped with A/C.

[Mark E.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

For the 1967 Corvette L79 (and I believe other C2 years as well), the redline was the same regardless of whether the car had A/C or not.

I have heard that for the C3 LT1, GM did have a problem with the A/C belt coming off, and this was responsibe for a delay in A/C being available with the LT1. My understanding is that GM "fixed" the problem by lowering the redline when the LT1 was equipped with A/C.

That's why I wondered if this was the case with L79 and AC.

[Neal K.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

FWIW...my '67 with C60 and PS.

Leif, although my 67 L79 with P/S and A/C is in storage and I can't recall all of the pulleys I do recall that the alternator pulley is a deep grove pulley. In your photos it looked to me like your alternator pulley has a standard grove. I think the assembly guide calls for a different pulley with P/S and A/C. I used that pulley. Your input will be appreciated.
Neal

[Joe L.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

Leif, although my 67 L79 with P/S and A/C is in storage and I can't recall all of the pulleys I do recall that the alternator pulley is a deep grove pulley. In your photos it looked to me like your alternator pulley has a standard grove. I think the assembly guide calls for a different pulley with P/S and A/C. I used that pulley. Your input will be appreciated.
Neal

Neal------


If your alternator pulley is a deep groove for the L-79 with C-60 and N-40 application, then it's either non-original or a factory mistake. I don't even see how it would align with the other pulleys you should have.

[Joe R.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

Leif, although my 67 L79 with P/S and A/C is in storage and I can't recall all of the pulleys I do recall that the alternator pulley is a deep grove pulley. In your photos it looked to me like your alternator pulley has a standard grove. I think the assembly guide calls for a different pulley with P/S and A/C. I used that pulley. Your input will be appreciated.
Neal

Hi Neal:

Yes, you are correct. I had forgotten this difference when I previously stated the the entire pulley set was identical to the base engine configuration.

The 1967 L79 with A/C *and* PS used the base engine standard groove pulleys for the water pump, crank, and PS pump. However, the alternator pulley was different from the base engine. It was part number 3846180, about 3" in diameter. Note that the diameter was smaller than the standard alternator pulley for the L79, which was about 3.6" in diameter. I think GM wanted to spin the alternator a bit faster on the A/C cars so that it could keep up with the higher electrical load of the A/C.

Regarding Joe Lucia's concern about alignment, I think GM determined that the slight misalignment with the other pulleys was okay because the alternator belt was so long. The benefit was that the deep groove pulley reduced the chances of tossing the belt at high RPM.

A few years ago Mark Gorney published a very comprehensive article in the Restorer regarding pulley sets for 1965-1967 small blocks. I belive this information is now incorporated into the JG.

Attached is a chart that I compiled some time back to compare some of the configurations for 1967. It's interesting to see how GM changed not just the groove width, but also the diameter of the pulleys as they sought to optimize a given configuration. If you look at the line called "Ratio to Crank" you can see the speed of the pulley relative to the crank speed. Note that for the A/C cars, both the water pump and alternator spin faster relative to the crank speed than the non-A/C cars.

[Joe R.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

You are correct 66 thru 68 used the standard groove pulleys, as I stated 65 is a 1 year only pulley configuration. The W/P and C/S pulleys are deep groove while the C/S add on and P/S pulley are standard groove. That is why if you look in the compressor mounting section of the AIM you will see 4 spacers at the mounting points of the compressor that will say "L79 only". This pushes the compressor out 1/4" to make up the difference in the W/P and C/S pulley widths since they are deep groove pulley's. Also in 65 the W/P with A/C pulley is a smaller diameter than the non A/C pulley. I think they did this to speedup the water pump so when the A/C was on the engine cooled better.

Hi Joseph:

Thanks again for your very helpful posting. I have been trying for years to get look at the 3868892 PS pump pulley, but these are very rare. My theory is that GM did not use a full deep-groove pulley set for the L79/C60/N40 because the tripple-groove stackup on the crank pushed the PS pump pulley too close to the frame rail. It seems that you have confirmed that for 1965 they used a standard-groove CS add-on pulley and a standard-groove PS pump pulley, combined with an otherwise deep-groove pulley set. That reduces the tripple-groove CS stackup height just a bit.

My guess is that GM found this still provided insufficient frame clearance over normal production tolerances, so for 1966-67, they threw in the towel and used a full standard-groove pulley set.

Given that the one-year-only pulleys are rare, I thought I would post some info that might help someone trying to find the proper pulleys for their 1965 L79/C60/N40 car. You mention that the the correct 3766987 dual CS pulley is functionally identical to the more common 3858533. I don't have a 3766987 sample, but photos on ebay suggest that the only difference from the more common 3858533 is the appearance of the front face, which would be covered anyway by the PS add-on pulley. So, perhaps the 3858533 can be substituted and will not be detectable in judging.

Moving on the the correct 3827843 CS add-on pulley, your description says that it is a standard-groove pulley that fits correctly inside the 3766987 deep-froove pulley. In my collection of sample pulleys, I have two standard-groove add-on pulleys that fit *almost* perfectly inside the 3858533 dual deep groove pulley. The part numbers are 346290 and 140231153. These two parts nest nicely inside the 3858533 and index well with the two raised collars on the 3858533, but they appear to fall about .050" short of bottoming in the 3585533. A simple .050" shim could be fabricated to resolve this.

In summary, someone who is trying to assemble a correct-looking pulley set for the 1965 L79/C60/N40 could probably use the above, easier-to-find substitutes for the CS stack-up and have a correct-appearing setup for judging.

Unfortunately, I do not know of any functionally identical equivalent to the correct 3868892 PS pump pulley. You could use the common 3770509, but it would sit about 1/4" father back than it should, and the misalignment would be obvious. To use this part, some clever shimming and/or machine work would be required.

[Joe L.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

Hi Joseph:

Thanks again for your very helpful posting. I have been trying for years to get look at the 3868892 PS pump pulley, but these are very rare. My theory is that GM did not use a full deep-groove pulley set for the L79/C60/N40 because the tripple-groove stackup on the crank pushed the PS pump pulley too close to the frame rail. It seems that you have confirmed that for 1965 they used a standard-groove CS add-on pulley and a standard-groove PS pump pulley, combined with an otherwise deep-groove pulley set. That reduces the tripple-groove CS stackup height just a bit.

My guess is that GM found this still provided insufficient frame clearance over normal production tolerances, so for 1966-67, they threw in the towel and used a full standard-groove pulley set.

Given that the one-year-only pulleys are rare, I thought I would post some info that might help someone trying to find the proper pulleys for their 1965 L79/C60/N40 car. You mention that the the correct 3766987 dual CS pulley is functionally identical to the more common 3858533. I don't have a 3766987 sample, but photos on ebay suggest that the only difference from the more common 3858533 is the appearance of the front face, which would be covered anyway by the PS add-on pulley. So, perhaps the 3858533 can be substituted and will not be detectable in judging.

Moving on the the correct 3827843 CS add-on pulley, your description says that it is a standard-groove pulley that fits correctly inside the 3766987 deep-froove pulley. In my collection of sample pulleys, I have two standard-groove add-on pulleys that fit *almost* perfectly inside the 3858533 dual deep groove pulley. The part numbers are 346290 and 140231153. These two parts nest nicely inside the 3858533 and index well with the two raised collars on the 3858533, but they appear to fall about .050" short of bottoming in the 3585533. A simple .050" shim could be fabricated to resolve this.

In summary, someone who is trying to assemble a correct-looking pulley set for the 1965 L79/C60/N40 could probably use the above, easier-to-find substitutes for the CS stack-up and have a correct-appearing setup for judging.

Unfortunately, I do not know of any functionally identical equivalent to the correct 3868892 PS pump pulley. You could use the common 3770509, but it would sit about 1/4" father back than it should, and the misalignment would be obvious. To use this part, some clever shimming and/or machine work would be required.

Joe------


Here are some photos of the GM #3868892 [not for sale], some showing it with a GM #3770509.

DSCN2106.jpgDSCN2108.jpgDSCN2110.jpgDSCN2111.jpgDSCN2112.jpgDSCN2113.jpgDSCN2114.jpgDSCN2117.jpg

[Joe R.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

Joe------


Here are some photos of the GM #3868892 [not for sale], some showing it with a GM #3770509.

[ATTACH=CONFIG]66817[/ATTACH]

Hi Joe L:

Thanks for the great photo comparison with the standard 3770509. In particular, the photo with them facing each other, propped up by the box, seems to confirm my expectation that the 3868892 places the groove about 1/4" farther forward. Can you tell us whether the diameters of the two pulleys are the same? They look quite similar in the photos, but a smaller diameter also helps with the frame clearance problem.

Since GM used the same PS pump on many other GM brands of cars, there are a LOT of PS pump pulleys out there that might come close to the ultra-rare 3868892. I have a few other PS pump pulleys in my collection, but as I recall I have not yet found one that would be a good substitute for the 3868892.

[Joe L.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

Hi Joe L:

Thanks for the great photo comparison with the standard 3770509. In particular, the photo with them facing each other, propped up by the box, seems to confirm my expectation that the 3868892 places the groove about 1/4" farther forward. Can you tell us whether the diameters of the two pulleys are the same? They look quite similar in the photos, but a smaller diameter also helps with the frame clearance problem.

Since GM used the same PS pump on many other GM brands of cars, there are a LOT of PS pump pulleys out there that might come close to the ultra-rare 3868892. I have a few other PS pump pulleys in my collection, but as I recall I have not yet found one that would be a good substitute for the 3868892.

Joe------


When my back feels up to the task, I'll try to dig them out.

[Joe R.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

Joe------


When my back feels up to the task, I'll try to dig them out.

Hi Joe:

Sorry to hear about the back trouble. I'm just recovering from a bout of that myself. No fun at all.

There is no rush on this. I'm just curious about the characteristics of the ultra-rare 3868892 compared to the common 3770509. By my calculations the 3868892 should sit about 1/4" farther forward than the 3770509. It is also possible that GM reduced the diameter a bit to help with frame rail clearance.

Regarding the difference in forward position of the groove, if you get these pulleys out I'd appreciate you taking a look at that dimension too. An easy way to compare them accurately is to grab a couple of sockets that are the same length. Then rest each pulley on a socket, with the pulleys face-up and next to each other. This indexes both pulleys to the surface where they seat on the pump, so you get a direct comparison of the difference in the groove centerlines.

Yesterday I looked through my collection of GM PS pump pulleys. I have one that's about 1/4" forward of the 3770509 but the part number is not visible. I have another that is about 1/8" forward of the 3770509, and when I googled the part number it turned out to be a fairly common Camaro part. I'm away from home right now and can't recall the number, but I can post it when I get home.

My thinking is that if this common Camaro part comes close to the offset of the 3868892, it might be possible to use it with a small shim as a substitute for the 3868892.

All I'm trying to do here is to come up with some alternatives for an unlucky person who has a 1965 L79/C60/N40 and does not have the correct original pulleys. The correct originals are hard to find, and when you do find them they are usually very expensive.

[Joe R.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

Yesterday I looked through my collection of GM PS pump pulleys. I have one that's about 1/4" forward of the 3770509 but the part number is not visible. I have another that is about 1/8" forward of the 3770509, and when I googled the part number it turned out to be a fairly common Camaro part. I'm away from home right now and can't recall the number, but I can post it when I get home.

My thinking is that if this common Camaro part comes close to the offset of the 3868892, it might be possible to use it with a small shim as a substitute for the 3868892.

All I'm trying to do here is to come up with some alternatives for an unlucky person who has a 1965 L79/C60/N40 and does not have the correct original pulleys. The correct originals are hard to find, and when you do find them they are usually very expensive.

Okay, I made some measurements on a pair of OEM PS pump pulleys. Power steering pump pulley number 3860457 is same 5.7" diameter as the common 3770509, but it places the belt groove about 1/8" farther forward (toward the radiator) than the 3770509. Both pulleys are standard groove and have a similar appearance. An ebay search on the 3860457 suggests it was used on Camaros and Chevelles.

By my calculations (not actual measurements because I've never gotten hold of a 3868892 pulley), the 3868892 probably places the belt groove about 3/16" to 1/4" forward of the 377509. So, the 3860457 Camaro pulley helps to make up some of the difference but not all of the difference. To move the 3860457 belt groove further forward, I think a shim washer could be placed on the pump shaft behind the pulley. The only factor that limits how thick this shim can be is that you need to retain sufficient threads to fully engage the nut that holds the pulley on the shaft.

So, this substitution, plus the two crankshaft substitutions that I mentioned earlier, can probably be used to closely replicate the one-year-only pulley set used on the 1965 L79/C60/N40.

[Joe L.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

Okay, I made some measurements on a pair of OEM PS pump pulleys. Power steering pump pulley number 3860457 is same 5.7" diameter as the common 3770509, but it places the belt groove about 1/8" farther forward (toward the radiator) than the 3770509. Both pulleys are standard groove and have a similar appearance. An ebay search on the 3860457 suggests it was used on Camaros and Chevelles.

By my calculations (not actual measurements because I've never gotten hold of a 3868892 pulley), the 3868892 probably places the belt groove about 3/16" to 1/4" forward of the 377509. So, the 3860457 Camaro pulley helps to make up some of the difference but not all of the difference. To move the 3860457 belt groove further forward, I think a shim washer could be placed on the pump shaft behind the pulley. The only factor that limits how thick this shim can be is that you need to retain sufficient threads to fully engage the nut that holds the pulley on the shaft.

So, this substitution, plus the two crankshaft substitutions that I mentioned earlier, can probably be used to closely replicate the one-year-only pulley set used on the 1965 L79/C60/N40.

Joe------


I'm not so sure a shim would work. These 63-74 power steering pump shafts and pulley centers are tapered. It's a slight taper but tapered nevertheless. A shim used to space the pulley forward would cause the pulley not to seat on the shaft.