69 belts and pullies

[Bob Lanham]

I asked a question similar to this awhile ago and got several answers about what size belts to use as long as the pullies were original in size. I have a squealing noise that I think may be caused by my belts. I've replaced 2 of the 3 and the noise has decreased a lot, vur I still have some. Before I forget - this is 69 427/390, with AC (not installed), power steering, and the AIR removed.

Someone in the past put a "captive" belt (crankshaft to water pump) that did not go around the idler adjuster. Joe Lucia told me previously that I needed a 34" belt and gave me the appropriate numbers. My question is now do I have the correct pulley? The pulley that mounts on front of the water pump has the number 3889372 BF. It also has an S stamped on the side opposite of the number. Is the pulley correct and will the 34" belt work? The belt I ended up cutting off is around 31" and was pretty tight.

[Joe L.]

Re: 69 belts and pullies

Bob----

Your water pump pulley, GM #3889372, is correct for your application.

With A/C and L-36 your car did not originally use a "captive" fan belt bewtween the water pump and crank pullies. There was an idler pulley located on the left side of the engine that made for an adjustable, "third pulley" in this system. Actually, this idler pulley makes for a much more convenient belt installation than the captive belt. If yours is not there, it means that someone must have removed it. If it were me, I think that I'd replace the idler assembly whether or not you plan to re-install the A/C. These assemblies are available in reproduction, albeit not inexpensively.

If you wish to install the captive fan belt as non-AC cars originally used, you need a 15/32" wide belt of 31-7/8" length. Originally, this belt was GM #3952336, but the only way you will get this size nowadays is to obtain a reproduction belt from Dr. Rebuild or others. If you wish to use a currently available GM SERVICE belt, most of which are 7/16" wide, you will probably need a belt of 32.0" length (GM #9433717) or 32.5" length (GM #9433718). If I said 34" previously, either I was just plain incorrect or I was basing it on some misunderstanding of your application.

[Bob #32271]

Probably my mistake

You originally gave me all of the part numbers and lengths for all of the belts for my car. I probably picked out the wrong number. The car does have the adjuster on it, but the belt was definitely the captive type. It was so tight I have no idea how they got it on the pulleys. Is 32.5 the correct length for a belt to use with the adjuster?

Thanks again for the help.

[Joe L.]

Re: Probably my mistake

Bob------

According to my information, the currently available GM belt to use with the idler pulley is GM #9433720. This is a 7/16" X 33.5" belt. Actually, this does not seem quite long enough to me given the fact that the captive belt is 31.5", but that's what GM says works.

Is the idler pulley currently installed but unused? I can't understand why anyone would go through the trouble of installing a captive belt when the idler pulley was present.

[Bob #32271]

Belt length

I agree that doesn't sound long enough. I don't know how you could get the captive belt on the pulleys if you were Arnold Schwarzenagger. I just bought an el cheapo belt that is 34 1/8". I think it will work OK with the adjuster.

Thanks again Joe.

[Joe L.]

Re: Belt length

Bob------

Captive belts are always a miserable experience to install and they were used on quite a few Corvette models over the years. That's why I don't understand why someone would overlook the idler pulley belt installation and go with the captive belt installation. I could understand it if someone had previously removed the idler pulley, but with the idler pulley just sitting there unused while someone struggles to install the captive belt seems rather insane to me.