Looking for advice on heater hoses (-65 Valiant, 225).

1. Hot coolant is propelled to the heater core from the upper outlet in the engine.
2. Somewhat cooler coolant returns to the lower inlet.

So far I think there is no argument.

But which is the "in" and which is the "out" on the heater?

When looking at pictures on internet, I've noticed that some have hooked the hot hose to the right (carburator side) and some to the left (fender side) heater connection.

Even my "1965 Plymouth Service Manual" has one picture where the hot goes in on the right side and one where it goes in on the left side (and yes, both pictures refre to the slant-six engine).

My logic says the hot should go in on the right (carb) side, as that seems to be higher up on the heater core. I guess the coolant does flow whichever way you hook it up, but should it not be more efficient if you hook it up the "correct" way?

My logic has been proven wrong before, so here I am, asking the wise people of slantsix.org, what say you?

Maurice

Dose one eat a hardboiled egg starting from the small or large end?

I don’t think it matters. Whatever hose connection looks neatest under hood is the way I would go. Leave heater hoses long enough to make valve cover removal easy for lash adjustments.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Later cars have different size heater hoses.

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Joshua

On my 1965 Barracuda, I have the hot water supply to the heater core going to the left side nozzle (looking towards the firewall). This causes hot water to flow to the bottom of the heater core and return from the top. This flow allows any air in the core to be more easily purged.

Thanks for the input everybody.

Your Barracuda idea about the air getting more easily out sounds good. I never thought of it that way.

I've just blindly followed the traditional "in-on-top" "out-on-bottom" principle seen on liquid-filled radiators (both on cars and in houses). The heater core is small too, so maybe it doesn't affect much the flow rate whicheer way you hook it up. And as you said, it sounds like the air might not get trapped so easily when the liquid exits high up.

My 1965 FSM also shows the heater inlet being the left side nozzle.

On radiators, any air circulating with the coolant will eventually come out in the upper tank. This allows the water pump to circulate cooled and air-free coolant from the bottom nozzle.

It probably doesn't make much difference either way. I had my heater hooked up backwards for many years (decades?) and I only corrected it last year when I cleaned out and rebuilt my heater assembly.