BB Waterpump Hub

[Kevin Whiteley]

I've been looking for a 3856284 BB waterpump for an April 68 coupe on and off. I've seen several, including a D 10 8, available and some have had hubs which have 8 holes. I concluded that 4 are for the small diameter bolt pattern and 4 are for the large diameter (71 - up?) bolt pattern.

However, this doesn't seem to make sense to me. If the large diameter bolt pattern came about in the 71 or 72 model year, why would an April 68 waterpump have a hub which supports the large bolt pattern? Are the 8 hole hubs "correct" for a 68 coupe? Would I be correct in assuming that the original hub was replaced for a "later" type?

I have pictures, but I will have to e-mail them. Thanks

[Joe L.]

Re: BB Waterpump Hub

Kevin-----

Original hubs had only 4 holes. When rebuilders get their hands on these cores, they often change these hubs to the "8 hole" variety in order to make the pumps have wider applicability for a given rebuilder's part number or to reduce the inventory of hub styles they must keep in stock. Also, the 8 hole hubs were often used on original SERVICE waterpumps. SERVICE waterpumps with 1968 casting dates were once-upon-a-time sold by GM (like for 1965 models having a waterpump replaced in 1968).

The additional holes in the hub are a moot point from a judging standpoint. There is no way that they can be seen with the pump and pullies installed on the car.