Discussion Forum - Northstar Chevelle Club

jim larson · 2K+ Club

What is best problem free 66 BBC alternator belt?

Jon H · 1K+ Club

Jim, I wouldn't be as worried about the type of belt used, as I would to make sure you have deep groove pulleys which are less likely to throw a belt.

jim larson · 2K+ Club

Jon H wrote:
Jim, I wouldn't be as worried about the type of belt used, as I would to make sure you have deep groove pulleys which are less likely to throw a belt.

In 66 they used a one pice pulley/. fan. Maybe the L78 used a deep pulley I will have to check into that.

Bobs_Place · Vice President

Jim

I used AC Delco belts. Seem to be good, I do have a belt chirp, maybe a harder compound.

Lost in the 60s · President

Back in "the day", the Dayco top cog was the only belt I could keep on my LS5/6 at high rpm. The cheap belts will stretch until they break or fly off.

jim larson · 2K+ Club

all the so called good belts won't fit, they all seem to have a width of 0.41 as opposed to the 0.375. as a result they don't fit down in the groove of the factory pulleys and are just a tad bit short. So its back to the cheap belt with save over all circumference. I will have to check that two cogged belt.

jim larson · 2K+ Club

Found the Dayco product . Dayco says to use 15495; but who knows if it will fit? Specifications say width is 0.44 and circumference looks like it will work. Amazon says it will not fit the chevelle. Who Knows? But free returns.

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-- Edited by jim larson on Monday 27th of April 2020 08:40:34 AM

-- Edited by jim larson on Monday 27th of April 2020 08:41:40 AM

Lost in the 60s · President

15495 is the P.S. belt.
The alt belt you need WITHOUT factory A/C is 15565
With factory A/C is 15560
This is right from the Dayco website.
Must be a pulley size difference as the belt for A/C is 1/2" shorter than without.

Bobs_Place · Vice President

Mitch you are correct, both pulleys are different.

Without A/C water pump runs almost 1 to 1 with the crank.

With A/C the water pump run about 20% faster than the crank.

jim larson · 2K+ Club

Hey guy I just realized that this morning. I do need the PS belt because as that got thrown along side the road and is long gone. I will also buy the alternator/ fan belt and use the one I just put on as a space in the trunk ( If I don't forget to take it and the tool kit along). Thanks

Also you can't just throw on a deep groove pulley as the center line is different and then you have to use other pulleys and belts.

One guy on TC made kind of a belt retainer out of a carriage bolt and piece of copper pipe slide over the bolt which would be mounted to the alternator bracket to keep the belt from being thrown. I bet I would get a couple of "what that".

-- Edited by jim larson on Tuesday 28th of April 2020 07:05:30 AM

Lost in the 60s · President

Bobs_Place wrote:
Mitch you are correct, both pulleys are different.
Without A/C water pump runs almost 1 to 1 with the crank.
With A/C the water pump run about 20% faster than the crank.

Interesting, so for people having slow speed/idle issues with overheating, the use of the smaller A/C pulley to move more coolant may help ?

67ss · 1K+ Club

There is this option though not cheap and it looks like it requires deep groove pulleys according to the seller.

https://www.ebay.com/itm/Idler-Pulley-Assembly-1965-66-Pass-L-72-425-HP-1966-Chevelle-L-78-GM-3765393-/303510128813

jim larson · 2K+ Club

67ss wrote:
There is this option though not cheap and it looks like it requires deep groove pulleys according to the seller.

https://www.ebay.com/itm/Idler-Pulley-Assembly-1965-66-Pass-L-72-425-HP-1966-Chevelle-L-78-GM-3765393-/303510128813

I WOULD THINK SOMEONE COULD MAKE SOMETHING LIKE THAT. OR JUST A BRACKET THAT BOLTS TO THE BLOCK/HEAD WITH A BOLT OR BOLT AND PULLEY TO CONTROL THE BELT. For the time being, I will make sure I have a 1/2 wrench and a spare alternator belt. It kind of a hassle to change the PS belt, so I would have to apply a little more effort to steer the car.