A6 Compressor Pulley Size

[Mark E.]

What's the correct pulley size for the AC compressor on a 1970 454?

An internet search shows 5" and 5 3/4" are possibilities. I also see reference to 5 1/8", 5 1/4", 6" diameter pulleys. I suspect there are two diameters produced, and the other measurements are due to how it's measured. But I'm not sure.

The diameter of my current pulley is 5 1/4", measured outside lip to outside lip. It's just a bit larger than the hub. The larger pulley I sometimes see on cars (aka 5 3/4") is visibly larger than the hub.

Has anyone seen a listing of which cars used the larger diameter? High red line engines?

Nothing found with a search on this forum or the shop manuals.

[Larry M.]

Re: A6 Compressor Pulley Size

Mark:

Larger diameter clutch pulley used on small block SHP solid lifter engines in 64-65 time period. Smaller diameter used for the others. I know of only the two diameters used for the C2 and early C3 cars.

Dom will have the final answer if different.

Larry

[Mark E.]

Re: A6 Compressor Pulley Size

In similar threads, I found https://www.forums.ncrs.org/showthre...or-Pulley-Size

Joe L. says a '69 big block uses a 5" (aka 5 1/8", 5 1/4") pulley. Same for 1970?

Similar threads seems to work better than the search feature.

[Domenic T.]

Re: A6 Compressor Pulley Size

Larry,
Mark & I are in contact with each other on this one as his compressor is on my bench. About all I see are the so called 5 3/4 sizes which are actually a bit smaller than 5 3/4. I think the stock belt that runs the compressor has the answer to this if someone doesn't chime in with their size.

Dom

[Joe L.]

Re: A6 Compressor Pulley Size

Larry,
Mark & I are in contact with each other on this one as his compressor is on my bench. About all I see are the so called 5 3/4 sizes which are actually a bit smaller than 5 3/4. I think the stock belt that runs the compressor has the answer to this if someone doesn't chime in with their size.

Dom

Dom, et all------

From what I can determine, there were only 3 pulleys ever used on Corvettes with axial compressors:

GM #5914724-----used for 1963-64 with high performance. I know nothing about this pulley. It was discontinued without supersession in March, 1971:

GM #5914745-----GM says that this pulley is 5.0" OD; they actually measure 5-1/8". This pulley was used with compressors GM #5910717, 5910706, and 5910741. Possibly others.

GM #6550750-----GM says that this pulley is 5.58" OD; they actually measure very close to that at 5.65". This pulley was used with compressors GM #5910737, 5910738, and 5910740. Possibly others.

There MAY have been another pulley used in the 1974-76 period of GM #6551249. All I know about this pulley is that GM says it was 5-1/2" OD.

[Domenic T.]

Re: A6 Compressor Pulley Size

Joe,
Thanks from me even thou it's Marks thread. What I do know (that I was told) is that the 365 HP had the 6 3/8" OD pulley. All other C2's had what was called the 5 3/4" pulley, which never had a 5 3/4" OD, Somewhat smaller, around 5 11/16 OD. I don't have the 64 manual, but the 65 addresses the LOWER COMPRESSION piston. Now I have seen these in 1970's compressors, the lower dished pistons. They lowered the compression by a 1" X 1/10th inch dish on the piston top. That was most likely to compensate for high RPM along with the largest pulley 6 3/8".
What is odd is that they would push the brake and gas pedal at the same time by using the dish piston that was for high RPM and use a 5" pulley that increased RPM. Now that could be that the BB doesn't reach the SB RPM range? Why not passenger car pistons?
All the professed true Corvette compressors I worked on had the dished piston and the close to 5 3/4" pulley. Wish there was more known about compressors because I see a few places for casting dates that are on the same 6555302 back plate. Some are centered between the inlet and outlet ports and some are under the outlet port with the exception of 63's that are all the way at the bottom of the 6555302, and only have 3 mountings on the back plate instead of 4.

Dom

[Joe L.]

Re: A6 Compressor Pulley Size

Joe,
Thanks from me even thou it's Marks thread. What I do know (that I was told) is that the 365 HP had the 6 3/8" OD pulley. All other C2's had what was called the 5 3/4" pulley, which never had a 5 3/4" OD, Somewhat smaller, around 5 11/16 OD. I don't have the 64 manual, but the 65 addresses the LOWER COMPRESSION piston. Now I have seen these in 1970's compressors, the lower dished pistons. They lowered the compression by a 1" X 1/10th inch dish on the piston top. That was most likely to compensate for high RPM along with the largest pulley 6 3/8".
What is odd is that they would push the brake and gas pedal at the same time by using the dish piston that was for high RPM and use a 5" pulley that increased RPM. Now that could be that the BB doesn't reach the SB RPM range? Why not passenger car pistons?
All the professed true Corvette compressors I worked on had the dished piston and the close to 5 3/4" pulley. Wish there was more known about compressors because I see a few places for casting dates that are on the same 6555302 back plate. Some are centered between the inlet and outlet ports and some are under the outlet port with the exception of 63's that are all the way at the bottom of the 6555302, and only have 3 mountings on the back plate instead of 4.

Dom

Dom------

Well, I suppose it's possible that the 63-64 GM #5914724 was a 6-3/8" pulley. I have no information on it.

Otherwise, if there was a 6-3/8" pulley used on Corvettes, then it was a pulley that was never available in SERVICE. That would be extremely unusual but I suppose it could happen.

According to GM, the 5.0" GM #5914745 was used for most 1964-68 Corvettes.

[Tom L.]

Re: A6 Compressor Pulley Size

Not sure if this will help but the pulley on my '72 LS-5 is the smaller one. It is NOT the compressor that came from the factory (pulley maybe but I can't say for sure) but the AFTERMARKET belt that crosses over from the GM number fits perfect. When I put my a/c together I wasn't sure about the pulley either. From observations of other cars I've only seen the small pulleys on big block cars. In fact the only early 70's C-3's that I've seen with the larger pulley are '72 LT-1's w/ a/c. I can check the belt size later on if that will help. Good luck!

[Mark E.]

Re: A6 Compressor Pulley Size

Thank you, Joe and Tom.

A photo on page 173 of the current 70-72 JG shows a '71 454 with the small pulley.

Any owners of original 454 AC cars out there who can help?

[Domenic T.]

Re: A6 Compressor Pulley Size

Well,
I guess there is a lot unknown about these compressors back plate casting date location, pulley size and piston CR.
Out of close to 100 C2 compressors Iv'e done close to 100% had 5 3/4" pulleys while the big passenger cars had the 5". Camero and GTO came in with 5 3/4". The 365 327 had the 6 3/8", according to the original owner or owners. LICORVETTE had the 5 3/4 available for their C2's, and I saw the 6 3/8 advertised for about 250.00. The 5 3/4" was about 150.00. Don't see them any more, but have had owners call me for the 6 3/8". I have about 20 or more C3's out with 5 3/4".
We will never know. Try and tell one of the owners there pulley is wrong! Wish I had the old LICORVETTE book. Now this makes me question my sanity. Could have been dreaming and never saw this.
Being that there isn't a judging manual out there that addresses date code casting locations and pulley size, I guess whatever one wants they can have.

Dom

[Domenic T.]

Re: A6 Compressor Pulley Size

Well, my post didn't make it. I talked to LIC and they said they once sold pulleys, but the only one she remembers is the 6 3/8 that was stock on the 64 & 65 327 365 HP. No other info. Called a vendor and they just say 5" on all but can't measure! Called the repo manufacturer and he says he makes the BIG pulley for the 64 & 65 365 HP. He makes them to look original but does not know the diameter! makes them but does not know diameter?
So I say "yep, that's a 5" pulley". So seems that no one has a method or equipment to measure. As far as the manual, you will find the same pics in passenger car manuals as well as vette manuals on common items, so pics are not reliable.

Tom, you said your pulley is the small one. would that be the 5", 5 1/8" 5 1/4", 5 1/2" 5 5/8", or the so called 5 3/4" that was a bit under 5 3/4. The large was 6 3/8".

Mark, you have a 5910740 compressor foil, your pulley is to small, but who cares, it's a 5" somewhere pulley. Your pistons ARE Corvette pistons.

Larry my friend, don't measure yours, if it's original to the car you may find it near 5 3/4 OD.

I need to hide as I have installed the wrong pulley on about 100 compressors and actually believed the owner saying his compressor was original
to the car!
I have a late 71 on the bench with vette pistons that has the 5 3/4" pulley and am shipping a 67 with vette pistons out that he owned since new or near new, 5 3/4 pulley also?
I hate to say this but the compressor is the LEAST known for judging. Those guys don't have the info they need, where do you get it.
I'll stick my neck out here and ask, how can you tell a 63 late from a 73? Not all 70's compressors had the different back plate with the clutch cut out switch! The A6 was on about every car, truck, tractor, and yes on airplanes of their run.

Dom

[Tom L.]

Re: A6 Compressor Pulley Size

Don't feel bad. I've been in the refrigeration business for 30 years. No one cares about us until the food is spoiling, in the case of a/c guys it's the same story. My car, like so may had the a/c removed because it was too much trouble. Those of us that choose to restore high option cars are at a disadvantage.

Since pre-1972 production had a smaller number of cars produced with a/c (especially the desirable high hp cars) I guess the JG authors didn't focus on that. Like anything, if a change has to be made you have to volunteer. Not suggesting it, it's a job. But it's probably the only way. Most don't have the knowledge to deal with these systems, thanks for helping all of those that you have!!

[Mark E.]

Re: A6 Compressor Pulley Size

Thank you, Joe and Tom.

A photo on page 173 of the current 70-72 JG shows a '71 454 with the small pulley.

Any owners of original 454 AC cars out there who can help?

Input from owners of these cars is appreciated.

[Domenic T.]

Re: A6 Compressor Pulley Size

Mark,
At this point...I don't care what size pulleys are on compressors... I have been lied to and am guilty of 99.9% of what I restored. as larry said I have the last word, and that is DONE. No one with a vette has a ruler or tape measure. Scream about door jams and screwed up sealer around the door Wx stripping! No more restorations, I will do A6 compressors without a tag from now on... NO more restorations. Why don't vette owners buy the CHINA made? They are cheap and will last a few years! NOW, I am going to spend time with my family on weekends, and work on my own cars and airplanes. Funny what a glass of wine will bring out of a person.

Dom

[Joe L.]

Re: A6 Compressor Pulley Size

Mark,
At this point...I don't care what size pulleys are on compressors... I have been lied to and am guilty of 99.9% of what I restored. as larry said I have the last word, and that is DONE. No one with a vette has a ruler or tape measure. Scream about door jams and screwed up sealer around the door Wx stripping! No more restorations, I will do A6 compressors without a tag from now on... NO more restorations. Why don't vette owners buy the CHINA made? They are cheap and will last a few years! NOW, I am going to spend time with my family on weekends, and work on my own cars and airplanes. Funny what a glass of wine will bring out of a person.

Dom

Dom------


I would not get too upset about this. This is a forum for learning. If we all put our minds together maybe we can figure this out. That's really the fun of it. This is a hobby, not a religion.

By the way, I am particularly interested in the compressor pulley size for any 1965-68 with L-79, especially if the compressor and components are known-original. There's just got to be some of you out there with such an application that can report on this.