V-belt dimensions needed

[Mike G.]

The belts for my '65 300hp with PS and A/C are:
Alt: 3847710 PS: 3874424 A/C Compr: 3849085

My searching for the dimensions (top width & length) has turned up nothing that I'd want to rely on. Even the 53-82 parts catalog is basically no help on pre-67 cars.

Anyone out the have a Captain Midnight Decoder Ring for these OEM belts?? Just need top width and length. ()

ps: for now, don't want to go with the "correct" restoration belts for a couple of reasons.

[Duke W.]

Re: V-belt dimensions needed

They should be in the AMA specs, which are available from GM at no charge.

Duke

[Wayne M.]

Re: V-belt dimensions needed

The belts for my '65 300hp with PS and A/C are:
Alt: 3847710 PS: 3874424 A/C Compr: 3849085

My searching for the dimensions (top width & length) has turned up nothing that I'd want to rely on. Even the 53-82 parts catalog is basically no help on pre-67 cars.

Mike -- just in case you didn't have any luck with the AMA specs, here's what I have in my '65 P&A30 (and others found in '66 & 67) P&A30's:

3847710; 3/8" wide by 53_1/4" long
3874424; 3/8" wide by 36_1/2" long
3849085; 15/32" wide by 56_3/4" long

[Duke W.]

Re: V-belt dimensions needed

Be aware that many GM service belts are not always the same as what the plant installed. In many cases they may be wider/longer than OE.

This cost me two lower radiator hoses on my Cosworth Vega before I figured out the problem. I finally determined that the GM service belt was wider/longer than the OE belt, which resulted in the alternator having to be moved to near the limit of its travel to achieve proper tension, and this caused the belt to intermittently impinge on the bottom of the lower radiator hose, wearing a divit. The aftermarket keyed off the GM service, not OE data, so they were/are all wrong, too.

I finally took the original belt to an auto parts store that had a tool to measure belt length, and found a Dayco belt that was effectively an exact match of the OE belt's width and lenth - no more problems.

I bought a belt in a price leader line called "Dynaflex", which is made by Dayco and is a plain V-belt without those hideous "teeth" on either the inside or outside, and it's at least as durable as OE.

If you don't have a known original belt to measure, then the AMA specs should tell you the dimensions of the OE belts. Don't rely on service belt data in the P&A catalogs because the dimensions may be different - even for the earliest available service belt. GM consolidated service belts without a specific engineering review for each application - shame on them!

All the GM and aftermarket parts catalogs still show the "bad" belt for the Cosworth Vega.

Duke

[Mike G.]

Thanks Wayne

Turns out I didn't have any luck trying to locate the AMA spec.s.

So your info really helped me out. The aftermarket belts that I've turned up as being the closest:

3847710: Gates 7535 (.41 x 53.5)
3874424: Gates 7365 (.41 x 36.5)
3849085: Dayco 15570 (15/32 x 57.0) or 15565 (56.5) top-cog style

For the 3/8" top width, did not find the needed lengths. I expect the Gates .41's will work fine on my 300hp L75.