66 427 "284" Water Pump Bypass Fitting

[Peter M.]

I purchased a restored 284 BB water pump which was void of heater and bypass fittings. The heater fitting simply screws in to the threaded orifice while the bypass has a pressed in pipe fitting.

The bypass orifice has pipe threading in it which surprised me since I thought all 284 pumps had a press fit pipe for the bypass. Do you think this was a modification from some previous rebuilder or do some known original pumps have threaded bypass fittings ??

[Joe L.]

Re: 66 427 "284" Water Pump Bypass Fitting

Peter----

I have several NOS "284" waterpumps [none for sale], including a few with 1966 and 1967 casting dates. All of these use the pressed-in style bypass fitting. As far as I know, the "284" pump casting was designed for use with the pressed-in style fitting and I doubt that GM would have produced any finished pumps with this casting and threaded fittings. When GM switched to threaded fittings, they changed the casting (and casting numbers) partially for the reason of accomodating the change to the threaded by-pass fitting.

So, I would expect that this pump was modified by some previous owner/rebuilder. If the press-fit style bore were damaged in any way such that a press fit fitting would no longer seal, then the only way to salvage the casting would be to tap it for an NPT fitting.