[allenga]

Hi Guys, looking to put a by-pass valve in, want to keep coolant flowing while bypassing heater core. Want it to be cable operated or manual.

I am only seeing plastic valves in US. China sellers on eBay have metal ones.

Anyone go with a metal or plastic by-pass. Experiences?

Thanks!

[lust4speed]

Here's my opposing viewpoint. Pontiac originally took the heater inlet hose off the manifold crossover at the front of the engine which is the best place to have the warmest coolant for the heater core. Then they decided that they could save 30" or so of hose on every car by tapping off the rear of the passenger head. Considering that the stock heater nipple is reduced down to a 1/4" hole and the course through the heater core reduces flow even more, not much volume is robbed from the main cooling flow back-to-front across the head. The fact remains that any coolant removed at the back of the head is that much less available for cooling the head, and this bypassed coolant ends up going directly back into the water pump bypassing the radiator. Using a standard 3/4" NPT to 5/8" hose brass adapter that comes with the aluminum heads and has no restriction, a massive amount of coolant will be diverted from its cooling function that will loop around and not go through the radiator until subsequent passes when it mixes with flow that isn't diverted.

On my drag car there are simple pipe plugs in the heads, and my street car has manual shutoff valves on each heater hose to keep heat out of the interior during the summer.

If Pontiac was worried about any sort of symmetry they would have robbed both heads of coolant, but that would have at least negated any savings on the shortened hose. Sometimes the reason engineers do things is to satisfy the bean counters...

[Tom Vaught]

Outstanding Explanation Mick.

Pontiac really screwed up on that change.

I have mentioned dyno testing on a Ford Engine with the same water to heater strategy and it was well documented that the head flow on the passenger head was robbed by the rear pick-up point for the heater core inlet.

Very uneven coolant temps trying to cool that head with the right front of the head begging for more water flow to cool the head/combustion chamber area.

Tom V.

[dlloyd]

So if I am understanding this correctly I should be able to restrict the flow or shut off the flow back to the water pump from the head. I am bypassing the heater core and going directly to water pump on my 65 GTO.

[leeklm]

Also curious of anyone has used an electric 12v solenoid for their shutoff valve? Would be handy to just flip a switch!

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