Heater core plumbing

[ImNoSpaz]

I'm probably confusing myself by over thinking.

I have the 7.4 Vortec in the 67 with the reverse water pump. I'm doing the a/c and heater plumbing and am stumping myself on the heater valve. We put the 69? heater control in because it is vac control for the heater, and we didn't want the additional cable.

The water pump has no out/inlet port as others. It has the pad for a nipple or fitting but no threaded hole, but the radiator has a port just below the fill neck.

Here's where I get stuck. If I put the vac heater valve on the small heater core tube and then run it to the radiator, will it work? It will stop flow when A/C is on, but the heater core is still hot. If I put the valve on the larger core tube, it will stop flow (this hose goes to intake manifold) but the core will still be hot...right?

I assume the reverse water pump is just reverse as far as the blades turn, but does not effect the actual direction of flow, right?

I have done a whole lot of things both custom and resto, but have never even thought about heater plumbing other than 1 hose goes to the water pump and the other goes to the intake manifold. My bad and my head is hanging low right now.

[toolboxchev]

I would start with seeing how they are plumbed in the stock vehicles, both the old and your newer vortec.

Problem solving could start with keeping it simple.

[kwmech]

you are correct, the reverse pump does not change the direction of flow. So with that being said, both the water pump port and radiator fitting accomplish the same thing---they are both returns. To feed the core you'll need to come off the corner of the intake either in front or back on the pass side...which ever one is available. So in other words the valve would go on the 'feed' hose, not the return

[ImNoSpaz]

Originally Posted by toolboxchev

I would start with seeing how they are plumbed in the stock vehicles, both the old and your newer vortec.

Problem solving could start with keeping it simple.

Did just that today. Found a 70 c20 and an 80 1500 that were plumbed from manifold and radiator to heater core with the water pump port plugged. Not Vortec though.

[ImNoSpaz]

Originally Posted by kwmech

you are correct, the reverse pump does not change the direction of flow. So with that being said, both the water pump port and radiator fitting accomplish the same thing---they are both returns. To feed the core you'll need to come off the corner of the intake either in front or back on the pass side...which ever one is available. So in other words the valve would go on the 'feed' hose, not the return

Thank you. Will just need to change nipple size on manifold because every heater valve I find is 5/8". We were going backwards apparently