Heater Core, Inlet/Outlet?
 

I just stuck a 350 in my '60 F100 and up until now, have had the heater fitting in the manifold looped back into the fitting on the water pump. It's time to hook it all back up and I'm wondering if the heater core inlet and outlet are specific (directional) or if it doesn't matter which hose goes onto which fitting.

I wouldn't think it matters but I don't want to find out the hard way.

Thanks.

Well, it won't blow anything up, but hose placement will dictate how well you heater works and wear on the core.

The inlet nipple is the lower one and the exit nipple is the upper. This forces the coolant flow to fight gravity to flow and forces any air out of the core.

The heater inlet (lower) is supplied by the outlet on the intake manifold, and the heater core outlet (upper) routes back to the water pump stem.

Thanks Julie...

Now I know I hooked mine up bassackwards in my 53.' Oh well, sumthin else to change.

Howie

Wow, now I had THAT all bassackwards, too. I assumed the pump fitting would have been the pressure side supplying flow to the core.

Thanks AGAIN, Julie!

Nope, the separate water pump tube is a bypass of the thermostat that allows coolant to flow out of the manifold through the heater and get recirculated into the engine when the thermostat is still closed keeping coolant stationary in the engine - warming up until it reaches operating temperature!

So you get hot water right off the engine to the heater and then it gets sent right back into the engine to warm up some more.

Thus you'll get hot coolant to the heater core long before the radiator ever sees any.