Reverse Flow a Heater Core? Pros and Cons

[69hurstolds]

Just to clarify heater hose flow directions here- The A/G body Olds V8 heater core equipped with A/C gets it's supply from the 5/8" supply line which is on the passenger side back of the intake. It exits the engine through the flow cutoff valve and then the inlet of the heater core. The 3/4" outlet from the heater core hose normally runs across the intake manifold through the clip next to the choke cover (if equipped) and around the oil fill tube on the front of the engine into the "11 o'clock" intake port to the pump. The "12 o'clock" water pump inlet port accepts the bypass flow for the thermostat. These inlet ports direct the flow coming in to the center front (inlet) side of the impeller. There are 2 outlets to the pump and those are through the ports on each side of the front of the block and through the front cover plate.

5/8" supply side to the heater core.
3/4" outlet side of the heater core.

If you don't believe me, fine. But that's how it was designed to work from the factory. Flip over an Olds V8 water pump and you'll see the radiator inlet hose, and the other hoses flow come in to the front and center of the impeller. AKA the suction side of the pump.

 

[azmusclecar]

But what if you didn't? What if you left it alone for say, I dunno, nearly 40 years? What works for YOU may or may not work for other people. If you're starting in a good place, it's easier to keep it there. azmusclecar is starting out with a car that has sat for Lord knows how many years. So, there's that. Working with an unknown situation here.

I would agree, a backflush couldn't hurt. It's virtually free with nothing but a couple of hose connections to deal with. What's the worse that could happen? If water flows through it, that's a good sign. The thing springs a leak and he has to change it out anyway? Or it just cleans up as best as possible and run it if it holds?

There's also the question of the "air" side that you can't see. Does air blow out the vents strong going through the heater core? If the air side is fouled up, you have to consider that as well.

The air flow quantity seems to be compromised as well...........which I thought maybe was a blend door issue but now that you bring it up...
what good does a hot heater core door if no air can get past the coils to bring it in to the cabin? It still may be a blend door problem, not saying it isn't/

 

[403Olds]

But what if you didn't? What if you left it alone for say, I dunno, nearly 40 years? What works for YOU may or may not work for other people. If you're starting in a good place, it's easier to keep it there. azmusclecar is starting out with a car that has sat for Lord knows how many years. So, there's that. Working with an unknown situation here.

I would agree, a backflush couldn't hurt. It's virtually free with nothing but a couple of hose connections to deal with. What's the worse that could happen? If water flows through it, that's a good sign. The thing springs a leak and he has to change it out anyway? Or it just cleans up as best as possible and run it if it holds?

There's also the question of the "air" side that you can't see. Does air blow out the vents strong going through the heater core? If the air side is fouled up, you have to consider that as well.

For my case, I bought the car when it was 10 years old already, with questionable maintenance. I did it for the 11 years I owned it. Just sharing what worked for me.