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Cooling System - Headers vs Manifolds

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madams View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote madams Quote  Post ReplyReply Direct Link To This Post Topic: Cooling System - Headers vs Manifolds
    Posted: Aug/14/2022 at 7:41am
Do headers increase/decrease the heat load on the cooling system?  Seems like not having to cool a big chunk of iron bolted to the head would reduce the heat dumped into the radiator.

Conventional wisdom is that headers raise the under-hood temperature which suggests that the heat is dissipated by the headers rather than making it to the radiator.

Interested in some definitive info on both heat load and under-hood temps
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Aug/14/2022 at 9:23am
  Headers DO increase under hood tempratures.

Headers can make for vapor lock on a hot day.

Headers DO cause performance issues on a hot day.

Headers CAN cause a over heated intake heat (choke) stove at any speed especially idle.

So, the anwser is a bit clouded.

Having run into all the above I say YES, heat loading is greater with headers.

Eliminating the choke heat stove crossover eliminates most of the heat issue
and helps make for a cooler running engine anyway.

I block the heat crossover every time.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mopar_guy Quote  Post ReplyReply Direct Link To This Post Posted: Aug/14/2022 at 10:47am
While I agree with Boris on his observations, I don't think it adds to the cooling system load. I may be wrong but I don't see how it would unless the car is standing still for long periods, or in stop and go traffic where you could get some heat soak but there's still the fan to help push that out of the engine compartment.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 73hornut Quote  Post ReplyReply Direct Link To This Post Posted: Aug/14/2022 at 10:53am
Reduce internal friction by running highest pressure rated oil.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red Devil Quote  Post ReplyReply Direct Link To This Post Posted: Aug/14/2022 at 11:36am
Depends on the conditions where you are measuring.  If headers reduce the fuel consumed at the test point to yeild same power, by increasing efficiency, they should have a net decrease on cooling system heat load.   If they increase fuel consumed, i.e. worse efficiency under the test condition, a net increase.  So it depends.

Effect on ability of cooling system to reject heat is another consideration.   Headers generally have much more surface area than manifolds and radiate more heat.  If the average underhood temperature  increases,  the deta-T across the radiator likely decreases making the cooling system less efficient - especially at lower speeds, idling, stop-and-go traffic.

If average underhood temperature increases, it may also affect intake air temperaure and AFR.  The standard "upgrade" to headers and an open element air cleaner ingesting underhood air isn't ideal.

So lots to consider ;)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote devildog80 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/14/2022 at 3:58pm
Just a thought

I was taught the reason OEM manifold were cast, and not thin steel like a header, was the cast will transfer heat away from the engine best, thereby keeping the engine cooler by simple transference?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BBO UK Quote  Post ReplyReply Direct Link To This Post Posted: Aug/14/2022 at 4:21pm
Modern ceramic coated headers, together with a "wrap" reduce the heat transference under the hood a fair bit from bare metal so some modern technology may come to the rescue for people installing new headers.
Heat transfer from the manifold may also be reduced with an insulating gasket.
I doubt either setup has much effect on overall cooling load, but I`ve no facts to back that up with.
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