[1966Lemans]

I recently put one of these on the 3/4 line of my new engine:
https://www.amazon.com/gp/product/B09MQ1J55W/

It seems to be working fine with the flow to the heater core turned off for the summer.

[grivera]

Do you notice a difference?

[dataway]

They added the heater control valve to A-bodies in 69 correct? An actual water valve. On 68's there is no valve, just the air control to stop air flow through the heater core. But yes you still have a hot heater core sitting on the passenger side of the firewall.

[Half-Inch Stud]

Yea, i tuned the duct valve controls for best closure to assure the heat was isolated. ( btw a simple task but i failed at that ).

The real inetrest is to isolate the heater core on 95-97 Towncars because the AC control "malfunctions and blows hot heat while on AC. A digital reset will make AC cold again but some cars keep faulting. Design problem.

[i82much]

Originally Posted by PAUL K

I think one gets more heat through the floor boards from the headers than hot water circulating through the heater core. Plus running the heater on high can help cool the engine down if you get caught in a traffic jam and the temperature starts creeping up.... That's what summer time cruising is all about. Sweeting like crazy with the heat on high, windows down and showing off the Burger King drive thru rough idle camshaft.

been there and done that, running the heater to cool the car down ... good times!

[i82much]

Originally Posted by 77 TRASHCAN

Just put the valves inline, in the heater hoses. Circulate the coolant to bleed the air out, with the valves open. Then just turn them off in the summer.

i'm just trying to figure out if there is any benefit to letting the coolant circulate back into the hose by using a bypass instead of "deadheading" the coolant in the hose?

[1966Lemans]

Originally Posted by grivera

Do you notice a difference?

Not really. I just didn't want my heater core being hot in the summer.

[HWYSTR455]

Yeah, heater core blocking doesn't provide much help, better off insulating the floorboard and firewall. By blocking some of the radiant heat from other sources (than the box) overall you will get a better improvement.

You could insulate the box too, but it really isn't going to help much, not enough to make any kind of noticeable difference anyway.

After driving a while, put your hand on the box, the floor, and the firewall, can see where most of the heat is coming from.

In my bird, I removed the tar paper one time when I did a carpet and driving to the beach one time the side of my sneaker melted to the tunnel. And that was just from removing the tar paper.

Dynaliner (or the like) is not expensive compared to the Dynamat.

You can wrap a section of the exhaust too, but not only is it a pain and cost, it can hold moisture and rot the pipe.


.

["QUICK-SILVER"]

Originally Posted by i82much

i'm just trying to figure out if there is any benefit to letting the coolant circulate back into the hose by using a bypass instead of "deadheading" the coolant in the hose?

Drivers side goes out the front and through the radiator to be cooled.

Drinkers side recirculates back to the water pump and doesn't get cooled.

[HWYSTR455]

Yeah the back of the head hose goes to the heater core, the one from the core goes to the water pump.

So the one that goes to the water pump mixes with cooled coolant and goes back thru the engine. Has little to no effect on engine cooling.

But the added capacity of coolant the heater core supplies does have an impact on overall cooling. How much of an impact is debatable.

As previously mentioned, it does help 'burp' the system tho, along with the cover to intake passage. That is a positive effect, no doubt there.

I removed the vacuum valve on my 71 A-body AC car and it had no noticeable effect on cooling or heating. I now have a Vintage Air setup, which comes with a valve (electric), and did install it as directions outline, but if it ever fails I will omit it. I get 31-32 degrees at the vent.

I got that car with like 68k original miles on it, and the AC blowed so cold, you couldn't run it on high on the highway without freezing you out of the car. Without the valve, it might have made a 2 -3 degrees difference, if that. You could see your breath on a 100 degree day. I don't remember what vent temps were, but it was cold.

I drove that car without AC for a number of years, replaced a part here and there trying to get it to work, and finally gave up and got the VA setup. Drove it with no valve that whole time. Think my problem was a combo of a compressor failure, and 2 dead replacement compressors, with the addition of a failing vacuum control panel. And yes, ran a filter after the original compressor burnout.


.

[grivera]

Damn, Mike - 31-32 degrees? The lowest I recorded on the bird was 36.

[NeighborsComplaint]

Originally Posted by Half-Inch Stud

Didn't GM-Pontiac have 1 vacuum-pot controlled heater valve, like in 69-70 cars?

Yes, all '64-72 GTO's used a similar vacuum actuated heater control valve to adjust the flow of hot coolant through the heater core. The only difference was the manner in which it connected to the heater core and the orientation of the vacuum connection. They will fully shut off the flow of coolant through the heater core if functioning properly.

[b-man]

Originally Posted by NeighborsComplaint

Yes, all '64-72 GTO's used a similar vacuum actuated heater control valve to adjust the flow of hot coolant through the heater core. The only difference was the manner in which it connected to the heater core and the orientation of the vacuum connection. They will fully shut off the flow of coolant through the heater core if functioning properly.

I have a factory air conditioned 1964 Le Mans and there’s no valve of any kind on the hoses going into the heater core. The same on ones with a standard heater, no such vacuum actuated heater control valve.

Maybe later years but not 1964.

[NeighborsComplaint]

Originally Posted by b-man

I have a factory air conditioned 1964 Le Mans and there’s no valve of any kind on the hoses going into the heater core. The same on ones with a standard heater, no such vacuum actuated heater control valve.

Maybe later years but not 1964.

Here is the AC Delco replacement part for 1964 GTO ... if you can modulate the heater temp, then there must be a control valve.

https://www.carparts.com/details/Pon...ll%20-%20Parts

[b-man]

All cable controlled on 1964 GTOs no vacuum, there’s simply a metal elbow on the intake manifold for the heater hose connection. Heater temp is modulated by a cable operated flapper door in the heater box.

1965 GTO did go to vacuum controls.

I’ve never seen a vacuum valve like the one pictured on any of the ‘64s I’ve owned.

It’s listed as a big Pontiac ‘63 and ‘64 piece as well as a ‘63 -‘64 Tempest part so I think their application listings aren’t completely accurate.

[Formulas]

that heater valve doesn't look right at all most of them i have seen on cars like ours did not screw into anything they have a bracket attaching it to the heater a/c box and the heater hose slips on both ends.. i still have one in a parts box saw it a few weeks ago

[Formulas]

had to get into the parts box for another reason saw the valve took a pic.. 1970 Van Nuys 400 Formula With A/C

[JSchmitz]

I installed this one. I intended to play around with the flow to optimize. But haven't touched it.

[chrisp]

Blocking heater core will provide much help as no circulation to core means no heat to the core , may get a bit warm but not hot.

[dataway]

Originally Posted by NeighborsComplaint

Yes, all '64-72 GTO's used a similar vacuum actuated heater control valve to adjust the flow of hot coolant through the heater core. The only difference was the manner in which it connected to the heater core and the orientation of the vacuum connection. They will fully shut off the flow of coolant through the heater core if functioning properly.

I don't believe this is accurate. 68 A-bodies had no device to control flow of coolant through the core, they had a vacuum operated flap that controlled AIR flow through the core. The coolant flow through the core was 100% all the time. In 68 the hoses from the engine go straight to the heater core and back again, no interruptions. In 69 a coolant flow control valve was added in-line on a hose to the core, this valve DID control coolant flow through the core.