Technical SBC Water pump bypass port????

I have a gen 1 327. There is a bypass port on the pass side of the water pump. The port on the block is not drilled through to the water jacket. Does anyone know why there is this unused port?

 

Thats for a heater hose

 

Are you talking about this hole below the mounting bolt?

 

It's not a heater hose connection. The hole is about 3/8" dia. and it's located just under the water pump mounting bolt holes on the pass side. There is a port on the water pump that matches up to this port. The hole on the block is a blind hole. It's not drilled into the water jacket.

 

Yes Jim. It's the hole just under the mounting bolt holes.

 

It’s to bypass the thermostat when it’s closed. Some SBC used a bypass hose out the top of the pump instead of the port. I just drill 3 holes in the thermostat to allow for bypass in your situation.

 

Something to do with truck engines? as mentioned, there's a fitting on the top of some water pumps, used as a bypass on trucks, and for the surge tanks on 60s Vettes.

 

The Z/28 302 and the hi-perf 327's used a bypass.
My 327.

 

If you buy a gasket set for a SBC the is one of the gaskets for this style by pass. If the block doesn’t have it you cut off that section of the gasket.
If the block has it you must get the proper water pump or true up the hole and use a cup style freeze plug. With it there is no need to drill holes in the thermostat as this will cause the engine a slower heat up time…or choice.

 

Never seen a SBC without that hole, but that don't mean a thing.

 

I believe Vortec blocks don't have the bypass hole.

 

Yeah...NOT...a heater hose connection !
Too small, no threads...

Mike

 

I've seen a restored, 2nd gen Corvette fuely with a bypass hose up top.

Gary

 

This may help.

Keep in mind that ‘vortec’ heads don’t have the ‘flow port’ in them that feeds this bypass hole, so if you slap vortec heads on your pre 86 block you will need to use the intake to water pump bypass.

 

Back in the mid 60's when I was the truck mechanic's helper at a Chevy dealer, the water pumps came with a small plug to block that hole if the engine had a by-pass hose.