[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.


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