Got a question about waterpumps on SBC's...There are 2 mounting bolt holes on the drivers side but on the passengers side, there are 3 holes. The bottom one is not a bolt hole but is a passage from the block to the input side of the waterpump. Any ideas as to it's purpose? Thanks Fred P

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Fred P.

That is a water by-pass port. I driled and tapped it and installed a threaded plug and then drilled the center of the plug 1/8" to force more water to circulate through the radiator. Every little bit helps on a blower motor.

Joe
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Joe Garcia
http://50chevy.freeservers.com/

Thanks for the info Chevy. I was thinking that but dont understand the factory reasoning behind it. Since I'm gonna need all I can get, I'll probably do that too. Fred P
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Fred P.

Fred, I may be mistaken, but my understanding is that the bypass is there to allow water to move through the pump while the thermostat is closed. ----- If the bypass is closed or restricted, I believe the thermostat should be drilled to allow pressure relief from the outlet side of the pump. This may cause the engine to take longer to warm up to thermostat temperature (in cold climates), but will not affect cooling capabilities.

I agree with Bruce on this. If the water has no where to go when the T-Stat is closed it can actually add heat due to mechanical feriction if I remember my college physics correctly. It wo't hurt a centrifugal pump to run with a closed head though.