Fitting in head for heater core
 

I left the old fitting in the head that plumbs to the heater core when the heads were rebuilt. I understand these have a reducer in the fitting to reduce pressure to heater core. Can I assume this fitting still has that reducer and in good shape? Not sure how these are designed. The heads are on the motor and in car, but just double checking to make sure.

It's not a so much flow/ pressure reducer, it's a thermonic spring that chokes off the flow thru the Heater core until a high enough coolant temp is reached.

Do these things go bad? Can I assume if mine was left in head, it is functional and be fine?

If you put the head in a wash tub, you can hook a hose to a faucet that allows hot and cold water.
If still on the engine use longer hoses.
Rig up a hose that puts water into the passage at the front of the engine and look for flow from a hose attached to the fitting on the rear of the head. cold water first. Does the water flow a minimal amount?

Then turn the hot water on and let it flow thru the head, if the flow increased after a period of time the valve is working fine.

Tom V.

The nicely milled nipples retain the spring but the smooth replacement nipple simply reduces the inner I.D. to a quarter inch with a restriction.

I always thought the spring was compressed flat from coolant pressure flowing through it and restricted flow under higher RPM running. Now I'm going to have to dig out an older style nipple and see if it does expand out of the way with increased temperature.

I learn something new every day.

I assumed that it was a simple reducer, not thermostatically active. Looking forward to Mick's report.

The newer GM "quick coupler" on my pickup is a simple reducer. And I believe that Olds had a plain ol' reducer, too.

The real purpose of that spring is to allow the passenger side Head to warm up just as fast as the driver's side.

That is very true because IF the heads had different thermal conditions during the first 505 seconds of the EPA Emissions Cycle it would have been much harder to pass the dyno emissions test which was standardized in the early 70s.

Ideally you want all of the cylinders to cool the heads the same so that the carb calibrations could be the same bank to bank and not have one side of the engine making more emissions vs the other side.

The 1/4" orifice in the heater line was a fix many years ago that was done by the Ford Engineers after the Heater Cores were being damaged by high speed accelerations on the Mustang Police Cars. That orifice may still be available from Ford.

Some heater manufacturers bent the inlet side heater tube inward in 4 places and made a 1/4th inch "Square" flow area to reduce their warranty issues.

Tom V.

That's interesting. When I check the crossover with my infra red temp gun,(when idling,) the drivers side is usually 10 degrees cooler. I'll check it after a spirited run and see if that changes. The heater connection is one I got from Performance Years and was the one with the restriction. It's different from the one I took out which had the spring.

This motor was on the dyno and temp ran fine, but had no thermostat in at the time. After dyno I put thermostat in. I'm now mainly concerned about my new heater core when I fire this up in car for first time later this month. I can only hope my old fitting has either a reducer or the spring thermo inside.

If you buy a small piece of plastic dowel the same diameter as the heater hose inlet hose inside diameter and make the length 1 inch long with a 1/4" drilled hole in the center you will not need to worry about your new heater core failing under WOT testing.

Insert it about 4inches in the hose and then attach the hose to the right rear water fitting for the heater. Done deal. I have posted this for years on PY. Dick B and others I believe have done the mod. The Ford Motor Company has done the mod on their "interceptor" vehicles.

Tom V.

Here's a picture of the inside of that nipple.

Heated hose reducer Hest Fitting:

i used a copper pipe reducer a few times: Hammered in, and never got loose.
May have a head with Factory reducer: Hose gets in way of maint.


THIS: Prefer the 301 right angle Fitting for best Hester Hose lay.

I checked and the only heater nipple on my shelf is the new style. So while I can supply photos of it, I can't run the test on the old style spring to see how it reacts to heat.

Steve, if you get a chance drop the old one you have in a pan of boiling water and lets see if the spring changes shape. I'm still thinking that the spring is only a buffering mechanism to smooth out any pressure pulses generated.

I think that almost all heater cores came with a crimped in area on the copper inlet tube that should pretty much insure that more coolant can flow out than in, but seems like the engineers wanted a little more insurance to protect the heater core.

Thanks guys.

I will test it out tonight and report back.

Well looking at my nipple closer I think it either may be defective from age ( maybe over heating?) as it all ready extended some what.

None the less I heated it in water and it does show signs of expanding at 130 degrees.

Here's a question, is the long heater hose from the timing cover to the heater core a suction hose?

I'm sorry to hear that. Mine aren't as nice as they once were, either.

Head or intake manifold to heater core = supply side
Heater core to water pump inlet or radiator tank = return side (suction side)

Sometimes heater core hoses are the same diameter, other times the suction hose is larger than the supply side hose.

The cavity behind the water pump vanes has three sources of water to the water pump:
(one passage returns water from the water cross-over to the pump even if the thermostat is closed. The large inlet passage brings cooled water from the radiator, and the third inlet passage to the water pump inlet cavity is the return from the heater core).

All three see negative pressures.

Tom V.

Yes, I should have said heater hose Nipple to have been more precise.

My personal Nipples have been Sun burned a few times, but they still look normal, lol!