Thread: Another Pontiac for the firebird

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Ah, good point. Which is the source hose? The block rear corner or the water pump? Olds 403.

Originally Posted by firebird77clone

Ah, good point. Which is the source hose? The block rear corner or the water pump? Olds 403.

depends on which pump and rotation. old school was from the radiator and into the block then the heads and then back into the radiator. I'd take a guess that one side of the core goes to the pump and the other side goes to the block.

Originally Posted by firebird77clone

Ah, good point. Which is the source hose? The block rear corner or the water pump? Olds 403.

This vacuum diagram shows the water outlet at the top front, so the pump pulls suction from the radiator, pushing through the block.
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olds-403-vacuum-diagram.png
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Since the main hose flows back to the radiator from the top of the block/intake I think I'd put the valve in the line from the rear corner of the block, with the heater core return to the water pump, and I'd leave enough hose to be able to swap them at the core (if they're both same size), but I think you'll be good.