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I have a rebuilt water pump on my 64. The number on the pump is 30570 with the letter A below it. Also has the letter M with the letter S below it, inside an elongated circle. I was hoping Joe Lucia could indentify the pumps' application. Thanks, Joe in advance.
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Re: water pump application
Jack-----
What you have there is an aftermarket casting and not an original GM casting. The 55-68 small block Chevrolet waterpump has such a HUGE market (but shrinking) that many aftermarket castings were made for these. In fact, a single "generic" casting would fit virtually all 1955-68 Chevrolet, including Corvette, small block applications as well as 69-70 Corvette. Generic castings for these pumps are still being widely manufactured today.
I expect that the pump that you have has a boss on the top with a drilled and tapped fitting for NPT thread. This fitting is for external bypass and most "generic" pump castings have it. For your application, the fitting may or may not be used, depending upon which engine option that you have. 250 and 300 hp 1964 applications would not use the fitting and it would be plugged with a pipe plug. 365 and 375 hp applications would use the fitting and a short, 90 degree hose would run between the fitting on the waterpump and the front of the intake manifold.
If you have a pump as I described above, it is the "generic" equivalent of the GM #3859326 casting. Most of the aftermarket castings that I've seen very closely resemble this GM casting EXCEPT for "numbers", of course. I feel very confident that yours is one of them. I've never seen a generic equivalent of the small block without external bypass pump casting. I don't think that the aftermarket makes them since the one with the fitting will SERVICE both type of applications.
Depending upon which engine option that you have the following castings would be correct for your car:
250 or 300 hp-----GM #3782608 (no bypass fitting on top)
365 or 375 hp-----GM #3839175 OR GM #3859326 (with 1/2" NPT bypass fitting on top)
If you want to obtain a correct waterpump for your car, rebuilt pumps using the above casting numbers are not difficult to find, at all (except the 3839175).
Most 64 small block waterpumps were NOT dated. The exception was very late 250 and 300 hp with the 3782608 pump.In Appreciation of John Hinckley -
Re: water pump application
Joe, I just wanted to confirm my suspician that the pump is not correct for my engine, which by the way, is the 365 hp. The "generic" pump has been on the car at least 27 years and I want to use the correct one in my restoration. Any suggestions on how to obtain the "right" pump and why is the 3839175 difficult to find? Thanks again.Comment
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Re: water pump application
Jack-----
You can obtain a correct waterpump from many sources. You might try Bill Mock of Bartlesville, OK (has a classified ad in the Driveline), John Pirkle of Augusta, GA, or Goat Hill Classics of Long Beach, CA (advertises in the Driveline). To be completely correct, you will need a 3859326 casting with a 1/2" NPT fitting on the top. These are hard to find, though. You could also use a 3859326 casting with a 3/4" NPT fitting and a special reducing bushing installed. Cleverly and carefully installed, no one will know the difference after the waterpump is painted. The pumps with the 3/4" fitting are MUCH more common than those with the 1/2" tapping. It's not imposible that you could go to your local auto parts store, ask for a rebuilt pump for your application, and get one with this casting number. Ask to look through the pumps that they have on the shelf and you could get lucky.
The 3839175 casting was used from very late 1963 through 1964 on SOME 365 and 375 hp Corvette applications. It was not used on any other applications. Consequently, it's quite rare since not that many were ever made. You'd be best to assume that yours came with the 3859326. It's considered correct for your application so why go making things more difficult for yourself? Plus, at this point, there's absolutely no way to know, for sure, which pump that your car was originally built with.In Appreciation of John HinckleyComment
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Re: water pump application
Once again, Thank's Joe and Jack Humphrey who responded via email.Comment
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