[veet66]

There was a thread about installing a round piece of stock and drilling a hole in it to be installed into the heater hose to prevent the heater core from cracking under pressure.

Does anyone remember what size was the round stock? which hose to install it into? 3/4 or 5/8 hose? What size hole in the round stock do I drill into it?

Thanks,

[Tom Vaught]

The restrictor needs to be about 5/16" inside diameter. The outside diameter needs to be approximately 5/8" or slightly larger as the restrictor needs to fit snugly into the hose that goes to the inlet of the heater core from the rear nipple in the head.

Tom Vaught

[veet66]

Thank you Tom, that is what I needed.

[grivera]

Does anyone know if the heater control valve in a Vintage Air system will function as a restrictor?https://www.vintageair.com/instructi...New%20Kits.pdf

[grivera]

I moved/asked same question to the cooling section

[Cardo]

Isn't there already a flow restrictor in the nipple from the head to the heater core?

[grivera]

Originally Posted by Cardo

Isn't there already a flow restrictor in the nipple from the head to the heater core?

This is my Firebird which has e-heads. They don’t accept the factory style nipple.

[Tom Vaught]

Originally Posted by Cardo

Isn't there already a flow restrictor in the nipple from the head to the heater core?

.

Most of the nipples that people assume have a flow restrictor, in reality have
a "deflection device". The "deflection device" changes the direction of flow slightly but does not REDUCE the pressure spike cause by the massive increase
in the flow going to the inlet of the heater core.

Only way to do that is to reduce the "flow area" of the supply hose vs the inlet chamber volume in the heater core. (reduce the pressure spike).

Imagine getting hit with a normal Garden Water hose vs a Fire hose.
Pressure/force is much higher with the larger hose at higher pressure.

Ford Police cars now have this mod in all of their heater systems due to
repeated "out of service" heater core issues.

The info for the "mod" was just passed around to the Ford Guys.

Tom V.

[Dick Boneske]

The need for a restrictor in the heater core circuit is mainly a '64 and earlier issue- for Tri-Power, two barrel, and four barrel A bodies and big cars. There is no restrictor in the coolant circuit to the heater core on any of these cars. Any spirited driving increases the pressure inside the heater core, and often results in a leak.

My '64 GTO. when new, had multiple heater core failures. I remember replacing the core in 10 degree weather, and several times with less severe weather. Regardless of weather, it's not a pleasant job. After a few fixes, I left the one firewall nut under the fender off, so I wouldn't have to struggle next time.

After these failures, I figured out a simple fix for the problem. The smaller 5/8" hose is the inlet to the heater core. The fix is to take a piece of round stock, metal or plastic, about an inch long. Drill a 1/4" hole through the center. Install the round stock inside the 5/8" hose, either at the nipple on the intake manifold or at the inlet to the heater core..

I have never had a heater core failure after making this fix.

[hgerhardt]

Originally Posted by grivera

This is my Firebird which has e-heads. They don’t accept the factory style nipple.

No, those brass fittings that come with the E-heads do not have restrictors, but it's easy to make a restrictor with a 1/4-5/16" hole to press-fit into the fitting.

[Dick Boneske]

“No, those brass fittings that come with the E-heads do not have restrictors, but it's easy to make a restrictor with a 1/4-5/16" hole to press-fit into the fitting.“

You are correct. The aftermarket heads have no provision for heater circuit flow restriction. This is also true of many ‘65 and newer stock heater hose nipples that are press fit to the cylinder head. The factory did put a brass “deflector” in the nipple, but it’s likely not many remain in place.

The simplest way to protect the heater core is as I described above—a piece of 5/8” diameter round stock—either metal or plastic, with a 1/4” hole through the center. This can be stuffed into the 5/8” hose at either end.

I have a few feet of plastic 5/8” rod. I will send a piece with the hole if you pay shipping. Just PM me. Problem solved!

[grivera]

Thank you - PM sent

[grivera]

You can disregard, in a separate thread about Speedmaster heads 74Grandville said he found a suitable restrictor at Home Depot. I bought it and installed it today. Thanks for the offer - Will

https://www.lowes.com/pd/Hillman-2-C...B&gclsrc=aw.ds

[wolf]

I tapped the supplied heater hose fitting and screwed in a brass hex pipe plug. Then drilled out the center to I think 1/4".

[lust4speed]

I also put the restriction in the heater hose nipple. Problem with the restriction in the hose is the next person replacing the hose probably won't have any idea that there is something in the hose. Putting it in the nipple pretty much insures it will be around as long as the head. I like to put it in from the head side since there is more meat in this area.

[Tom Vaught]

What you did will work just fine on heads with a threaded head.
Plus the Restriction inside the nipple assures that the pressure spike will never leave the head and damage the heater core.

The insert in the hose is a simple quick way to protect the heater core but your idea, if you had access to the proper machines
to make the brass insert and press it in the nipple it IS a better fix.

Tom V.