Which water pump?

I just bought a box of assorted parts. An early model water pump was included (at least it was painted red so I assume it was from an earlier car.) The body of the pump is identical to the pump I took off of the 1972 18V engine except there are two holes on the shaft housing of the 18v engine pump, one of which is blanked off. The older pump has a stamped, metal impeller and the newer one has a cast iron impeller. All things being equal (condition of each pump) should I use the older, lighter pump or the newer, heavier pump.
Thanks

Tim

Edit: The shaft housing on the older water pump is about an 1" longer.

If you're fitting a plastic fan to the water pump you'll need the short nose pump, if you're using a metal fan you should use the long nose pump.

If you're using an electric fan it doesn't matter but I have heard of the stamped impellers falling off the shafts so I'd probably use the one with the cast iron impeller. Of course, as Jon said you'd need the matching pulley for the water pump, a shallow one for the short nose and a deep one for the long nose.

And to maybe confuse matters, but thats not my intention, there are spacers available but I'm not sure if they are for moving the fan fwd or bumping out the pulley on a short nose pump. Someone will know.
RS

Avoid stamped anything that's in rotation. I'd opt for the cast iron. When Quinton Hazel made stamped water pumps for the MGC, life span was expected to be about 6 months....FWIW

http://www.mossmotors.com/graphics/products/PDF/MGBwaterpumps.pdf

Tim. As Jon stated, the pump and the pulley have to match. Your '72 would have probably come with the shorter pump, and it's my preference, as it gives more room to work at the front of the engine.

The alloy bodied pumps with stamped impellor are ok. They work, but I prefer the cast iron impellor.

Installing a used water pump of dubious provenance is a bit like reusing a condom. It might work out ok, but the implications if it doesn't, make spending the money on a new one a good call.

kelvin

The water pump for 65-71 cars measured 4" from the base of the mating surface to the base of the pulley attachment flange. The 72-80 water pump was 3" for that measurement. Both are readily available for around $40-45. Basil

18???? You got to stop at 18????? Lucky!!!!!

Thanks guys. The older pump seems to be in marginally better shape but by the time I fit new spacers or a different fan the cost of a new pump shrinks considerably. And thanks for the condom advice. I think I'll throw away this one I've had in my wallet since 1966.

Tim

LOL!! Tim

cheers