[remy30006]

My original heater core doesn't look bad but it has deposits inside. is there a way to get it flushed out? my engine will be rebuilt and don't want gunk floating through. If its better to replace it, does any body have a recommended brand? They seem to range from about $30 to over $100. Not sure what would make that much difference.
Thank you!

[Tom Vaught]

Whatever you finally come up with, if a new core, do the mod on the inlet side to restrict the slug of water damaging the core or put the 5/16" id restrictor in the inlet line like Dick B did on his car.

Tom V.

[tempest1964]

Tom,
I remember reading about this some time back. Now I am at the point where I need to do it. I searched "heater core restrictor" and couldn't find it. I went to Summit and looked up Mustang heater core restrictor and that didn't work either. Seems like I remember that there was a Mustang part that would work. Maybe you or Dick could chime in.
Thanks,
Tony

[pfilean]

The restrictor is not that hard to make. Has been discussed here many times and a little searching should give several ideas. But doing something is a must. Unless you like soaked carpet and working while standing on your head under the dash.

[tempest1964]

Ok, ok! Lol. As usual, I overthought it. Instead of typing in " heater core restrictor" I just typed in restrictor and there it was. Thanks

[Rich-Tripower]

Why is a heater core restrictor needed?

[GT182]

Remy, I got one for my 66 thru O'Reilly Auto Parts about 3 years ago. Was $39 and change back then and looked just like my original heater core.

Here's a link..... https://www.oreillyauto.com/shop/coo...ttr_10078=Show All.

Part #: 94539 for 65, 66, 67 ac and non ac. I didn't check but possibly for 64 too.
Brass and copper for $43.95 with free shipping.

[Goatracer1]

If you look at the original core you will notice the inlet tube of the core has the opening slightly bent inward from the manufacturer. This is your restrictor.

[tempest1964]

Originally Posted by Rich-Tripower

Why is a heater core restrictor needed?

Rich, there has been a lot written about too much pressure (especially on high performance engines that rev quickly-which send high pressure pulses to heater core) blowing the heater core. Dick Boneske detailed making a plug 5/8 X 1-1/2 long with a 3/8 thru hole to insert in the small hose to prevent the pressure pulses from blowing out the heater core. He recommended brass, aluminum or even plastic. Just not steel- no rust.

[GT182]

I've had no pressure related problems with the one from O'Reilly. And the inlet tube of the core has the opening slightly bent inward like the original. Like I said... I've had no problems with their replacement core.

BTW... save the thick foam 2 hole "gasket" that slips over both tubes to seal the hole in the fire wall, where they go thru it. I could not find a replacement like it anywhere from anybody.

[Tom Vaught]

Originally Posted by tempest1964

Rich, there has been a lot written about too much pressure (especially on high performance engines that rev quickly-which send high pressure pulses to heater core) blowing the heater core. Dick Boneske detailed making a plug 5/8 X 1-1/2 long with a 3/8 thru hole to insert in the small hose to prevent the pressure pulses from blowing out the heater core. He recommended brass, aluminum or even plastic. Just not steel- no rust.

It is not so much a bunch of small pressure pulsations that kill the core but the massive slug of water that fires down the inlet hose when the engine goes to WOT. That TIDAL WAVE of water fires thru the hose like a bullet and smashes into the back wall of the heater core, eventually failing the core. The restrictor blocks some of the water's energy and the reduced flow diameter of the water and then the expansion of the water diameter after the restrictor kills even more of the waters energy.

Ford Cop Cars were killing lots of cores (due to abrupt WOT situations) until "the MOD" was incorporated.

[Jeff Hamlin]

[remy30006]

That is awesome information, I had never heard of the restrictor. Is there a seal that goes behind the heater core in the box or between the heater core and the firewall?
Thank you!

[Tom Vaught]

If you purchased a replacement heater core from GM, after your core failed, then you got the factory "modded" smaller square opening core. About a 1/4" square opening.

If you bought a NAPA core or other replacement core in the 60s/70s, it MIGHT or MIGHT NOT have the "MOD" on the inlet tube of the heater core.
So sometimes you had to do the "MOD" or you just replaced parts and blew out the replacement core in a short period of time too.
I was told about the "MOD" by our Head Mechanic in my Uncle's Pontiac Dealership. Have done the "MOD" on any car that I knew was going to be raced.
Ford Mustang Cop Cars in the 80s got the Restrictor "Mod" after blowing out heater cores based on a suggestion from a Research Guy.
The did not want the techs bending inlet tubes. they wanted a idiot proof (cut the hose, install the restrictor, add clamps) type service fix. It worked too.
Plastic part is no longer in the old Mustang cop car system but probably the part is there for the new modern Ford Police vehicles.
Dick B has posted info on how he makes his plastic restrictors for his cars.

Tom V.

[John V.]

Great info! I've been around a long time and never knew about this issue.

I will check this out on my heater core.

One thing I can add, my early car is using the molded rubber seal as seen in the Illustration for the heater hoses in the Shop Manual, pg 12-5

At some point, the molded rubber seal was superseded by a thicker foam rubber seal.

Here is a thread where the early molded seal mounted externally was discussed vs. the thicker foam seal that was apparently mounted internally.

http://forums.maxperformanceinc.com/...d.php?t=748069

[Dick Boneske]

Based on the aftermarket cores I've seen, I would keep the original even if it costs much more to rebuild it. The new ones are very fragile compared to OEM and they don't fit the housing--all I've seen are too small.

The mention of the restrictor above is critical for a '64. Just take a piece of 5/8" round stock about 1 1/2" long--metal or plastic--and drill a 3/16" hole through the center. Insert it into the smaller of the two hoses at either end. This will ensure the core doesn't blow the first time you "exercise" the engine!!

[tempest1964]

Hey Dick, I thought you posted 3/8 thru hole on another post. Maybe I'm just confused?

[Tom Vaught]

Originally Posted by tempest1964

Hey Dick, I thought you posted 3/8 thru hole on another post. Maybe I'm just confused?

In this thread http://forums.maxperformanceinc.com/...ick+restrictor Dick B said 1/4" hole in the restrictor and gave the other dimensions. Not 3/8" though

Tom V.

[MUSLCAH]

Will this restriction plug ,help with any cooling....as in lower temps ?

[Tom Vaught]

Originally Posted by MUSLCAH

Will this restriction plug ,help with any cooling....as in lower temps ?

Hard to read your question twice.
The mod is designed to remove the slug of water traveling down the hose and impacting on the back wall of the heater core and eventually causing it to fail (leak).

Under normal conditions the heater core would see the same temperature water but with slightly less water flow (so maybe the defroster takes a slight bit more time to un-fog the windshield).

Lower Temps? NO. Only way to get that deal would be to add a A/C Water Control Valve (that stops the heated water flow Normally when the A/C System is on).

Tom V.