1972 Corvette Big Block Water Pump Casting # ?

[James W.]

I've got a fairly unmolested 1972 Big Block Coupe (I'm third owner and car hasn't seen the street in some 25+ years - the second owner had it from April of 1973). The water pump is casting # 3992077 with a cast date of E 19 71 - May 19, 1971. The car was built according to the trim tag B27 - September 27, 1971. This pump is for a 1971 big block car according to the 1970 - 1972 judging manual. The casting # for the 1972 big block is 386100. Could the water pump I have be original to the car? I understand the 6 month rule for most cast dated parts, but do to the casting # could I have a replaced water pump? Would this be judged as the incorrect water pump?

Thanks,

Jim

[Patrick H.]

Re: 1972 Corvette Big Block Water Pump Casting # ?

Jim,

As a judge, the first thing I would look at is whether or not your water pump appears to ever have been removed. Are you getting it road-ready and keeping it original? Is it undergoing a full restoration? Does the water pump"appear" to have been factory installed?

Now, having said that, do I think it might be original? Yes. My own 71 small block's motor was built in June of 1971. Yet, my water pump was built in August of 1970. It had never been replaced nor off the car. In addition, the 1971 casting is relatively uncommon, so the "odds" of the right casting but a "bad date" ending up on the car are VERY small. Thankfully the date on a small block's water pump is not noticeable.

So what to do? I would personally leave it alone, or if you are having it rebuilt I'd go ahead with that. I've learned that certain components, like water pumps and alternators, seemed to have a mind of their own when it comes to the 6 month rule.

Patrick

[Joe L.]

Re: 1972 Corvette Big Block Water Pump Casting # ?

Jim------

The GM casting #3992077 waterpump was used for Corvette big blocks for BOTH the 1971 and 1972 model years. If the 386100 was used, at all, for the 1972 model year, it would only have been for very late in the model year. I have no doubt, at all, that the pump that you have is original to the car. In any event, the dates "work". And, as I say, I would contend that the casting number works, too.

For me to believe that the 386100 was used for the 1972 model year I'd have to see one with dates which could be correct for a 1972 model year car. Even then, if they were, say, June or July, 1972 dates, I'd expect that they were destined for a 1973. I think that there's a greater possibility that 3992077 pumps were originally installed on early 73s than the 386100 were installed on late 72s.

[James W.]

Re: 1972 Corvette Big Block Water Pump Casting # ?

Joe and Pat,

Thanks for the info. I'm planning to rebuild the pump since it has been sitting for 25+ years.

Jim