Pulley Part Number

[Jimmy G.]

I need help to identify a pulley GM part number 3991425. Looks like a smog pulley but not in my knowledge bank. Any help appreciated

[Michael H.]

Re: Pulley Part Number

Jim,

Joe Lucia usually takes care of all the part number questions but it looks like he's taking the night off. Your 3991425 is a water pump pulley and is listed in group 1.062 as fitting 71-75 all with 350. It may also fit some 76 and later cars but my book only goes up to 75 so I'm not sure.

[Joe L.]

Re: Pulley Part Number

Jim and Michael-----

Yes, GM #3991425 is a waterpump pulley. It's a single groove, AIR pump drive pulley. It is used in PRODUCTION for most, but not all, 1971-81 Corvette applications with AIR. It "sandwiches" onto the front of a GM #3991423 or 3991424 waterpump drive pulley and was never used for any "stand-alone" application, at all.

It was replaced by pulley GM #14023158 for 1982 PRODUCTION applications and that pulley also became SERVICE for all previous 3991425 applications when the 3991425 was discontinued from SERVICE in January, 1982.

As far as cars go, all of the aforementioned pullies are Corvette-only pieces. They were not used for other applications, although there is a slight possibility that they may have been used for some MD/HD truck applications.