Water pump identification

[Mark A.]

I have a water pump I am trying to determine if it is a corvette pump or not. It is a #3869328. Date code is B-18-8. Anyone know what this is out of? Also what year is the date code? Thanks for helping. Mark

[Joe L.]

Re: Water pump identification

I have a water pump I am trying to determine if it is a corvette pump or not. It is a #3869328. Date code is B-18-8. Anyone know what this is out of? Also what year is the date code? Thanks for helping. Mark

Mark-----


Well, we know the number is not 3869328 for 2 reasons:

1) There never was a waterpump of casting number 3869328

2) GM #3869328 was a blue vinyl seat back upholstery for a 1965 Corvette.

Anyway, I believe the number you're referring to is GM #3859326. Casting numbers are very often difficult to discern correctly.

The GM #3859326 casting was used for 65-67 Corvettes with small blocks using EXTERNAL bypass as well as certain other 66-68 Chevrolet small blocks using external bypass (L-79 Chevelles/Chevy II and Z-28 Camaro).

The casting date on the one you refer to is either February 18, 1968 or February 18, 1978. I believe the 3959326 casting was out-of-production by February 18, 1988, but it's possible it was still being produced at that time.

All examples of the 3859326 used on Corvettes or the other Chevrolet models I mentioned had the upper bypass fitting drilled and tapped for 1/2" NPT. Later SERVICE versions of the casting are tapped for 3/4" NPT since these castings were also used for SERVICE for certain trucks that used the larger fitting.