Big Block Water Pump info??? (Short)

[kcandc]

I bought a short big block water pump for my 68 396 project and would like to I.D. it.
The casting # is 336100, it may be 386100, but I'm sure it's 336100
The part number on the GM box is 3990993.
Anybody know what this is for??? Thanks, Karl

[bertfam]

I believe the 3990993 number is a new number for the short BB pump. Can't help you with the 336100 number, sorry.

Ed

[My68SS]

An old thread in need of an update. Seems 386100 may have been the actual number and after doing a google, looks to be mentioned in 'Chevrolet by the numbers 1970 - 1975'
My casting - 3856284 which appears correct for 68 396.
What was the original shaft diameter? Mine has a 3/4" size, should it be 5/8"?

[Jerry@CHP]

284 is the correct WP casting number for '68,

Jerry

[My68SS]

Thanks Jerry, do you know what the pump shaft diameter for 68 L34 396 is - 3/4" ?

[Jerry@CHP]

I'll have to check one for you when I have a minute. 

Jerry

[My68SS]

Just a prompt bump for Jerry or anyone on this shaft diameter detail as above

[1968RSZ28]

Hi Rob -

  If I'm reading the drawing correctly in the book "Chevrolet by the Numbers 1965-69" the shaft diameter for water pump casting number 3856284 is .64" which is about 5/8"  (5/8" is .625" to be exact).

Paul

[JohnZ]

The 284 casting was machined in two configurations. The one used on BB Corvettes from '65-'69 had the big bearing, a 3/4" diameter shaft, and a 5/8" pilot with a 3" bolt circle on the hub. Starting in '71, all Corvette water pumps went to a 3/4" pilot and a 3-1/4" bolt circle on the hub.