326 w/p

[Gary P.]

Do all original 326 and 609 W/P come with only 4 holes for the fan. Or do some come with 8 holes.

[Alan D.]

Re: 326 w/p

All the original one's I have seen (although limited number) have 4 holes. My understanding is that the multi hole units were later for convenience of re-builders.

[Joe L.]

Re: 326 w/p

Do all original 326 and 609 W/P come with only 4 holes for the fan. Or do some come with 8 holes.

Gary------

I doubt that any '609' waterpumps used in PRODUCTION ever had anything other than "4 hole" hubs. It's also unlikely that any '609' pumps once sold in SERVICE ever had anything other than "4 hole" hubs, either. That's because while these things were available in SERVICE or used in PRODUCTION there was no application I know of that used the large bolt circle mounting pattern. So, there would have been no need for "dual pattern" ("8 hole") hubs.

The '326' is a different story. While most PRODUCTION waterpumps using this casting were probably fitted with "4 hole" (small bolt pattern) hubs, a large number of '326' castings waterpumps were sold in SERVICE for many years and way beyond the time that this pump was used in PRODUCTION. These SERVICE "326' pumps usually have the dual pattern hubs. Some very old NOS examples from the mid 60's might not, though. Could some original '326' pumps used in PRODUCTION have the dual pattern hubs? I'd say it's remotely possible but unlikely since I don't think there were any applications which used the large bolt circle pattern during the time the '326' pumps were being used in PRODUCTION. The last year that a '326' pump was used in PRODUCTION for any Chevrolet model was 1968 and their use for that model year was very limited. However, if any dual pattern hubs were used in PRODUCTION, I would say that 1968 would be the most likely year.

[Terry M.]

Re: 326 w/p

Not quite what you were looking for, but just another stick in the ground:

My 1970 LT1 Trim tag date January 29 (A29) has a #3782608 water pump, Casting date: L 12 9: December 12, 1969. It has never been off the engine since the engine was assembled at Flint on January 14, 1970. It has 8 holes on the flange -- both the large and small diameter bolt patterns.

It is of course just one data point, but one you can take to the bank.