Mr. Joe Lucia, Could You Help Me Verify Some Part Numbers?

**Joe L.** · May 6, 2020, 05:02 AM

Re: Mr. Joe Lucia, Could You Help Me Verify Some Part Numbers?

Originally posted by Russ Trotter (15044)

Joe,

I am working on an early 1968 427/435hp with A.I.R., body build date: Sept. 5, 1967.

This car is missing the entire A.I.R. system, and I wanted to replace it (and some other parts) with all of the
original part numbers. I already have a restored A.I.R. pump. My sources are the "1968 Corvette Assembly Manual" and the "Corvette Parts Book".

A.I.R. Pump Pulley .... #3925522
Water Pump Pulley .... #3883235 or #3848904
Water Pump "Add-on" Pulley ... #3765427
Water Pump ... #3977630
Fan Clutch ... #3916141
5-Blade Fan ... #3740523 or #3883235
Crankshaft Pulley ... #3850838 or 3860010

I pulled the crankshaft pulley the other night, and it's not even a Corvette P/N,
although it did come off of a Chevrolet big block. I'm not sure that the 5-blade
fan is stamped with a part number.

Any help you can provide would be appreciated.
Thanks for all you do!

Russ Trotter
NCRS #15044

Russ-------

A.I.R. Pump Pulley .... #3925522---this is correct; discontinued without supersession in October, 1979

Water Pump Pulley .... #3883235 or #3848904-----1st design used 2 groove pulley GM #3848904 with 1 groove add-on pulley GM #3883235. 2nd design used 3 groove pulley GM #3888366 with no add-on pulley. 3883235 was discontinued without supersession in July, 1984. GM #3848904 was discontinued in September 1972 and replaced by GM #3995641

Water Pump "Add-on" Pulley ... #3765427------ 3765427 not used; this is a small block pulley; see above

Water Pump ... #3977630----This part number did not even exist in 1968. Waterpump used was GM #3876173 or 3927564. No matter which as both are identical, these numbers appear nowhere on the pump and both use casting GM #3856284 (which is cast on the pump). Both waterpumps were discontinued in 1969.

Fan Clutch ... #3916141-----Most likely this was the fan clutch used. It was discontinued about 10 years ago. Later production MIGHT have used GM #3937771 which is an entirely different configuration. It was discontinued in February, 1980 and replaced for SERVICE by the 3916141.

5-Blade Fan ... #3740523 or #3883235----3740523 is a spacer, not a fan. It MAY have been used with 1st design waterpump pulleys. 3883235 is the 1 groove add-on pulley, not a fan blade assembly. Fan blade assembly used was GM #3888366. This is a 5 blade assembly with no part number stamped on it. It was discontinued in April, 1971 and replaced by 7 blade fan GM #3955182

Crankshaft Pulley ... #3850838 or 3860010----GM #3850838 is a small block crankshaft pulley not used on big blocks. GM #3860010 is the harmonic balancer used for your engine, not a pulley. The pulley used for your engine was supposed to be a stamped steel pulley of GM #3921923. However, I believe that most, if not all, 1968 L-71 were fitted with a cast iron pulley of GM #3863108. Both of these pulleys are functionally interchangeable. Both are discontinued.

I do not know when 1st design pieces changed to 2nd design.

**Russ T.** · May 6, 2020, 11:46 AM

Re: Mr. Joe Lucia, Could You Help Me Verify Some Part Numbers?

Thanks Joe for your invaluable assistance.
Some of these parts are getting pretty expensive, and I
want to be sure that I'm buying the correct ones.

Russ Trotter

**Joe L.** · May 6, 2020, 08:44 PM

Re: Mr. Joe Lucia, Could You Help Me Verify Some Part Numbers?

Russ------

One thing to keep in mind: the 1968 1st design 2 groove waterpump pulley was 5.89" OD. The 1968 2nd design 3 groove pulley was 5.5" OD. This means that the 2nd design pulley drives the waterpump and fan at a faster speed for any given engine speed. The faster speed and consequent better cooling is not a bad thing for a big block Corvette.

Mr. Joe Lucia, Could You Help Me Verify Some Part Numbers?

Mr. Joe Lucia, Could You Help Me Verify Some Part Numbers?

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