1964 engine pulleys

[Geoff B.]

I have a 64 L76, no air, and am trying to determine if I have the correct water pump pulley and crankshaft pulley. My water pump pulley is 7 1/8 diameter. The judging guide calls for 7 1/2. Is this correct? I can not find anyone selling a 7 1/2 water pump pulley. Does anyone know where I can buy one?

For the crankshaft pulley the judging guide calls for a 6 3/4 pulley, #3744043, for cars with air, but does not specify a size or part # for non-air cars. Does anyone know what the size is for non-air cars? The one I have has the part number refernced in the judging guide for air cars, so it seems that is not correct for my non-air car, but the judging guide is not very specific on this.

[Wayne M.]

Re: 1964 engine pulleys

I have a 64 L76, no air, and am trying to determine if I have the correct water pump pulley and crankshaft pulley. My water pump pulley is 7 1/8 diameter. The judging guide calls for 7 1/2. Is this correct ? ....

For the water pump pulley, going out on a limb, here, because I don't have a '64 or the '64 books. You should have pulley # 3770245 which is 7_1/8", per GM parts catalogs. The one below is either off a '64 or 5, and has no part # stamped on it. It has its original paint, which I would describe as more gloss than semi-gloss, after wiping vigorously with Varsol on a rag. Notice the distinctive lip where the forward belt groove part was pressed on the cone.

Ignore the reinforcement/spacer -- this pump had it, but I believe not TFP for this pulley application.

[Joe L.]

Re: 1964 engine pulleys

I have a 64 L76, no air, and am trying to determine if I have the correct water pump pulley and crankshaft pulley. My water pump pulley is 7 1/8 diameter. The judging guide calls for 7 1/2. Is this correct? I can not find anyone selling a 7 1/2 water pump pulley. Does anyone know where I can buy one?

For the crankshaft pulley the judging guide calls for a 6 3/4 pulley, #3744043, for cars with air, but does not specify a size or part # for non-air cars. Does anyone know what the size is for non-air cars? The one I have has the part number refernced in the judging guide for air cars, so it seems that is not correct for my non-air car, but the judging guide is not very specific on this.

Geoff------


With one caveat if the car is a later 1964 L-76, I believe the waterpump pulley should be the GM #3770245 as pictured by Wayne. The GM spec for this pulley calls for it to have an OD of 7.1" . The caveat is that, according to the AIM, later 1964 L-76 was supposed to have used pulley GM #3850141. This pulley did once exist but I can find no indication that it was ever cataloged in SERVICE for any Corvette application. The only application I can find is a late 1964-1965 passenger car with 409 application. Might it have been used on late 1964 Corvettes with L-76? Yes, I suppose it MIGHT have been so-used. I have no information on it, though.

The crankshaft pulley should be a 2 groove pulley of GM #3766987. However, it's very possible that your car actually used a GM #3858533. Even though the AIM does not show it, I believe that the changeover from the 3766987 to the 3858533 occurred sometime in mid-to later 1964. In any event, both pullies are functionally interchangeable and virtually identical in configuration. They have a GM spec OD of 6.8" and 2 grooves. Both are "deep groove" pullies.

[Joe L.]

Re: 1964 engine pulleys

For the water pump pulley, going out on a limb, here, because I don't have a '64 or the '64 books. You should have pulley # 3770245 which is 7_1/8", per GM parts catalogs. The one below is either off a '64 or 5, and has no part # stamped on it. It has its original paint, which I would describe as more gloss than semi-gloss, after wiping vigorously with Varsol on a rag. Notice the distinctive lip where the forward belt groove part was pressed on the cone.

Ignore the reinforcement/spacer -- this pump had it, but I believe not TFP for this pulley application.

Wayne------


A very curious thing I've noticed is that the vast majority, if not every, GM specification for pullies calls for them to have the "GM" trademark and part number embossed on them. Yet, I have seen numerous original GM pullies, both PRODUCTION and SERVICE, that had no part number and/or no "GM" embossed on them. The one you picture is a perfect example. The spec of the GM #3770245 definitely requires the part number to be embossed on the pulley and embossed somewhere on the outer surface of the cone section. Yet, none apparently appears on this pulley as well as other pullies of this part number I have seen.

While many, many GM pullies have no part number on them, if there was ever a part that needed to have a part number emplaced on them it would be pullies. Although they failed to require a part number on many other parts, they did specify it on pullies. How the suppliers got away without doing it I can not figure out.

[Geoff B.]

Re: 1964 engine pulleys

Thanks Joe, great info! My car is a Nov. 63 car. Do you have any idea as to why the judging guide lists a 7.5' OD for the water pump pulley? It seems like the only place I can find reference to that size pulley is in the judging guide so I'm wondering if it's a missprint.

[Joe L.]

Re: 1964 engine pulleys

Thanks Joe, great info! My car is a Nov. 63 car. Do you have any idea as to why the judging guide lists a 7.5' OD for the water pump pulley? It seems like the only place I can find reference to that size pulley is in the judging guide so I'm wondering if it's a missprint.

Geoff-----


There are several different "measuring points" for OD on this pulley. The specs are different for each point. In other words, if you measure the OD "between the grooves" you should get an OD greater than that at the rear which is where the pulley is commonly measured. In any event, if you have a pulley configured like the one in Wayne's picture, you have the correct pulley.

[Geoff B.]

Re: 1964 engine pulleys

Ok. Thanks Joe. Do you have any knowledge about the second part of the original question regarding the harmonic balancer pulley?

[Joe L.]

Re: 1964 engine pulleys

Ok. Thanks Joe. Do you have any knowledge about the second part of the original question regarding the harmonic balancer pulley?

Geoff-----


The GM #3744043 pulley was used for some C-60 applications. It's a standard groove pulley and was not used for 1964 L-76 applications. The balancer pulley used for 1964 L-76 applications was either the GM #3766987 or the 3858533 each of which is 6.8" OD.

The GM #3858533 remains available from GM to this day. So does the 3744043, but you don't need that one.

[Geoff B.]

Re: 1964 engine pulleys

Thanks again Joe.