1970 Water Pump Hub

[Juliet P.]

What size / configuration is the hub on your original water pump (the part where the pulley bolts up to)? Is it the smaller diameter size where the spacing between adjacent holes (studs) is 1.5" or is it the larger diameter where the spacing between adjacent holes is 1.7"? Does it have a single set of 4 holes in it, or two sets of holes? I'm specifically interested in 1970 small blocks.

My original waterpump is long gone. I pretty sure that I should have the small diameter hub as my pulley appears to be the original. However, I'm uncertain if it should have a single or double hole pattern in it. From Joe Lucia (28 Dec 1999, archives MIA) "Your original water pump pulley should have been GM #3876846 which has now become GM #3995642. It is still available for a GM list price of $44.45." Thought I'd save you some retyping Joe. However if you can add to the singe / double set of holes discussion that would be most helpful.

Thanks, ~Juliet

http://www.1970corvetteregistry.org

[Robert C.]

Re: 1970 Water Pump Hub

There are one set of holes(double sets and slots instead of holes are for universal application). The hole pattern for 70'is smaller in diameter than 71 and 72.

[robert leazenby]

Re: 1970 Water Pump Hub

my 70 has only one set of holes, smaller diameter. However I was just reading yesterday that the 70 service manual (69 copyright) calls for replacement pumps to have two sets of holes for more applications.

[Joe L.]

Re: 1970 Water Pump Hub

Juliet-----

Your original water pump hub had only one set of holes for the pre-71 bolt pattern. PRODUCTION water pumps used previous to 1971 were usually always made this way. However, all SERVICE water pumps of the 55-70 style usually have the dual-pattern. Most commercial rebuilders replace the single pattern hubs with the dual pattern in order to increase part number applicability.

[Clem Z.]

Re: 1970 Water Pump Hub

the pulley flange on water pumps can be replaced with any other flange,all you need is a arbor press. the pump does not have to be taken apart just remove the back plate so you can press the flange back on.

[Clem Z.]

PS

there are 2 different size pump shafts,5/8" and 3/4" diameter so these flanges are not interchangable.