Water Pump Date Code Format

[Mark E.]

Re: Water Pump Date Code Format

Mark------

Generally, yes. However, it would be possible to use a 3992077 casting and use the 65-70 bearing assembly (i.e with 5/8" pilot) and the 65-70 hub pattern or a dual pattern hub (the hub OD was the same or nearly the same for 65-70 and 71-74). So, as far as I know, the factory could have used the 3992077 casting to make up a 1965-70 pump.

Possible. But I've never seen a 2077 with the small hub, and it sounds like you haven't either.

The JG says they're out there. It's questionable the '70 fan would fit on the larger hub. I have an aftermarket large hub clutch and the '70 fan does not fit over it. So the 2077 pumps used in '70 probably have the smaller hub unless a different fan is also used.

This is my speculation since I have not seen this.

[Joe L.]

Re: Water Pump Date Code Format

Possible. But I've never seen a 2077 with the small hub, and it sounds like you haven't either.

The JG says they're out there. It's questionable the '70 fan would fit on the larger hub. I have an aftermarket large hub clutch and the '70 fan does not fit over it. So the 2077 pumps used in '70 probably have the smaller hub unless a different fan is also used.

This is my speculation since I have not seen this.

Mark------


I have seen 3992077 pumps with dual pattern hub and 5/8" pilot. However, I've yet to see one with a 1970 date. Since there were no 1971+ applications I know of, and certainly no passenger car applications, for a short leg pump with small bolt circle and 5/8" pilot, I have to assume these pumps originated as SERVICE pumps for 1965-70 Corvette applications. Or, they went through a commercial rebuilding operation and were, thus, converted to a "one-size-fits-all". With the simple addition of a 5/8" to 3/4" bushing, usually supplied with the rebuilt pump, these pumps can be used for either 1965-70 Corvette applications (bushing unused) or 1971-74 Corvette applications (bushing used).

Fan blade assemblies do not, of course, mount to the water pump hub. However, I know of no GM fan clutch that will mount a pre-1971 fan blade assembly and have a large bolt circle hub. There are now 1971+ GM fan clutches with dual bolt pattern hubs which will mount to 65-70 waterpump hubs. But, these fan clutches all require a 1971+ fan blade assembly.