1973 SB Air Conditioning Belt - Need Some Help

[John S.]

I just ordered a set of GM Restoration fan belts from Quanta, everything was going great until I tried to install the A/C belt. I loosened the compressor and had it pivoted inward as far as it would go (hitting the valve cover) and the belt was not even close to going on. Checked the length of the new belt and it is 58" per Quanta spec. Checked the length of my previous aftermarket belt and it is 59".

Called Quanta and they confirmed that the 58" belt is the only one available A/C belt for SB's in 1973, mine is an L82. They said they make a 59" A/C belt for 1974 but it is slightly wider (.437 vs. .375) and the P/N and date would be incorrect.

I bought this car from the original owner last year and it has turned out to be a very original unmolested car. Has anyone else had issue with a "73 A/C belt ?? Like I said, there was no more adjustment inward, all off the mounting brackets match up with the AIM and the compressor model and date code match up with the rest of the car.

I suppose one or both of my engine pulleys could be incorrect (too large), but the alternator and PS pump belts fit fine. Does anyone have the correct P/N's and/or diameters for the engine and water pump pulleys or any other ideas that might help me out ??

Thanks

[Edward J.]

Re: 1973 SB Air Conditioning Belt - Need Some Help

John, you might be able to put the belt on compressor pulley first then the crank next and then try to slip over the water pump last. Or unbolt fan and remove the pulley off the w/pump studs, then slip belt over pulley and then slip back over studs.

[John S.]

Re: 1973 SB Air Conditioning Belt - Need Some Help

Thanks Ed, I'll give that a try first thing tomorrow AM. I will be very surprised if it works, but never say never.

Thanks again !!

[Jack M.]

Re: 1973 SB Air Conditioning Belt - Need Some Help

The data in the FREE Information Kits from GM (see STICKY) does confirm your A/C belt to be 58.00" x .380" (PDF page #50).
There may be more significant details in the kit... worth downloading and taking a look.

[Harmon C.]

Re: 1973 SB Air Conditioning Belt - Need Some Help

The 59" that is wider would be my choice cause the wider belt would be more like the original in width. If you are having the car judged the 3 or 4 belts have 4 points so one belt with a wrong part number would be .2 deduction so you would be ok.

[John S.]

Re: 1973 SB Air Conditioning Belt - Need Some Help

Thanks for the input guys but after 4 hours my 59" aftermarket A/C belt is back on the car.

Forgot I already had the '73 packet download from the Heritage Center, it confirmed the 58" belt spec but nothing further about the pulleys - Thanks Jack.

Ed's idea of removing the WP pulley almost worked, it was sooooo close to going on !!! If it was 1/2" longer I think it would have worked.

So on to Phase II of the project - while I had the fan and WP pulley off I figured only 4 more bolts and I can have the crank pulleys off to verify P/N's and diameters. Here's what I found and it concurred with the '73 AIM, (measurements were not specified, just reference dims I took with a tape measure while the pulleys were off):

WP pulley 3991424 - page 251 w/C60 A/C - 6 1/8" OD
Main crankshaft pulley 3911013 - page 247 L48/L82 w/C60 - 7 5/8" OD
Crankshaft add-on PS pulley 3751232 - page 247 - 6 3/4" OD

With the pulleys off and documented I returned to the A/C unit and mounts, all three pieces are cast and installed per the illustrations on pages 257 and 261 of the AIM, no adjustment found other than the original pivot and swing of the A/C compressor. The A/C compressor and pulley appear to be original with the correct model number and date code. So what gives !!??

Refusing to give up, I'm back to the 58" belt supplied by Quanta. Took it to three different auto parts store and had it measured. I wouldn't call measurement of the belt with the devices I seen an exact science, but the longest measurement I could get from the three different stores was 57 1/2", kinda sounds like the 1/2" I mentioned above ??

Gave Quanta another call, asked if they had or knew what the manufacturing tolerance might be on this size belt..............ahhhhh, maybe 3/8" or so, we'll measure it when you send it back. So I'm sending it back for their review, very convinced there is nothing wrong with my car.

I'll post an update when I get their reply, anybody from Quanta an NCRS member ?? Is there anybody else who is licensed to repro these belts ??

[Edward J.]

Re: 1973 SB Air Conditioning Belt - Need Some Help

John, one more detail is to remove the compressor adjuster bolts completely, sometimes this will let the compressor rest on top of valve cover. I have a 72 L-48 and when I installed a set of aluminum covers this is what I did. and again try the pulley un-bolt if this does not work.

[John S.]

Re: 1973 SB Air Conditioning Belt - Need Some Help

Thanks Ed, but I think for now this one is back in Quanta's court. I have my suspicions that the L82 valve covers are a bit taller than the standard steel covers and do not allow the compressor to pivot in as far, but I have to believe the belt I have is undersize and/or below tolerance. Give me that 3/8" tolerance on the other side of the 58" spec and I'd be a very happy camper !! Perhaps thats why they went to a 59" belt in '74 ??

Not having my car judged until June of next year so no big hurry. Just a bit OCD when it comes to getting things right, but I'm sure I'm preaching to the choir on that one. Thanks again.

[Harmon C.]

Re: 1973 SB Air Conditioning Belt - Need Some Help

Is your original A/C belt the wider size? They set higher in the pulley and look more original than a 3/8 belt and drive the A/C better.

[John S.]

Re: 1973 SB Air Conditioning Belt - Need Some Help

Lyle - my original (aftermarket) belt is a bit wider @ .410", the Restoration belt measured .390". Not a whole lot of difference but I imagine that the aftermarket belt sits a bit higher in the pulley. Really can't compare the fit of the Restoration belt because I was never able to get it all the way on.

The Restoration belt is on it's way back to Quanta, hopefully I can get this resolved with them. My fall back plan is the 3rd Qtr. '74 59" belt, but I certainly hope I don't have to go there, Thanks.

[Paul B.]

Re: 1973 SB Air Conditioning Belt - Need Some Help

John, if you're interested, I have a Quanta belt B-254 for a '75 Corvette #9433769 which says it is ".440 x 58.50" on the belt. Box says effective size 7/16 x 58.50. It's yours if you want to try it. Part # on the belt in white letters says " GM 9433769 HB Gates(in small oval) .440 x 58.50 8136 T1 ".

[John S.]

Re: 1973 SB Air Conditioning Belt - Need Some Help

Thanks for the offer Paul, I'll keep it in mind. Hopefully Quanta can resolve this issue with a belt that will fit, we'll see. Thanks again !!

[Edward M.]

Re: 1973 SB Air Conditioning Belt - Need Some Help

I assume that your A/C compressor has the correct deep groove pulley? I don't recall the exact details, but the pulley on Corvettes was a deeper groove than other GM models of that year.

I'm sure someone can jump in with the details.

[Ralph S.]

Re: 1973 SB Air Conditioning Belt - Need Some Help

In 1983 I changed all the belts on my 1973 L-48 the belts are still on there, the A/C belt is GM9433769 HB 440X58.5 DAYCO 42-3561 the belts were purchased at a local Chevrolet dealer at the time. I am the original owner of this car.

[Edward M.]

Re: 1973 SB Air Conditioning Belt - Need Some Help

So I would like to follow up on this thread. What does it do to the fan belt fit if you have the wrong pulleys at any location.
I have seen so many C3 Corvettes with generic rebuilt A6 compressors that appear to have the wrong size pulley for a Corvette.

Wasn't one of the reasons that you could not get A/C with the LT-1 engine until 1972 is that they engine would throw the compressor fan belts. Didn't Chevrolet put a special deep groove pulley on the A/C compressors for LT-1 engines in Corvettes and Z/28 cars.

I know that the pulley is generally considered "part" of the A/C compressor, and compressors had different part numbers based on applications.

Does this sound right?

This is an A/C compressor pulley that I took off of a 73 base motor car back in 1989. The bearing had seized up.