Why intake manifold requires heat.
 

Here is an interesting article helping explain why sustained moderate heating of the intake manifold is beneficial. See the attached link:


Why you need to heat your intake manifold | Langdon's Stovebolt

Yup...it provides a stable environment for the intake system. Using water heat/coolant stabilizes the intake temperature to about the same temperature range that the thermostat provides for temperatures within the engine.

Good find on that article!

Excellent article, and comes up way too often. I'm making this a sticky!

Thanks, AbandonedBronco! :-X22

Well, this is a "one-size-fits-all" solution, but you just might be "solving" a non-problem. Or a seasonal problem.

First, your new aluminum intake manifold sits directly above the hot exhaust manifold. Maybe there's plenty of airflow between the two, but maybe not; in my old '66 Econoline, the "doghouse" engine compartment got quite hot in the summer, stock intake manifold got VERY hot even with the flapper valve in the exhaust manifold wired permanently open, and the carb would vapor-lock in slow traffic.

So I don't think there's a single answer here, even given that we're talking daily-drivers, not racecars. What's YOUR installation, what's YOUR climate? Does YOUR engine actually NEED additional manifold heat for good mpg and driveability when it is fully warmed up? Maybe you only need extra heat for cold start and warm-up. In that case, a modern style air-cleaner with a snorkel-door and hose that draws hot air off the exhaust manifold, and shuts off later, might be all you need. Are you in San Diego or Fairbanks?

I like the idea of a hot-spot created by hot engine coolant rather than one created by much hotter exhaust gases. And you can put a cable-control knob in your dashboard to throttle the hot-spot water flow. We inline-six fans have it good here; running coolant through the exhaust crossover passage in a V-8 intake manifold is a good idea but more trouble to do.

One thing drivers in Fairbanks know, and those of us in the Lower 48 need to learn, is the value of a good 120VAC plug-in engine heater. Especially in winter, and engine heater reduces engine wear and improves mpg. It is the ONLY system that is instantly effective on start-up.

I've looked into electric heat for the intakes, but could never find anything that didn't take an hour or so to come to full temp. I'd love to find something along those lines.


Before I had heat on mine, I do distinctly remember putting my hand on the underside of the intake on a 100° day after driving for two hours, and it wasn't even hot. This is after sitting directly above the exhaust manifolds for two hours. So yes, it's necessary! :D

"One thing drivers in Fairbanks know, and those of us in the Lower 48 need to learn, is the value of a good 120VAC plug-in engine heater. Especially in winter, and engine heater reduces engine wear and improves mpg. It is the ONLY system that is instantly effective on start-up."

I learned the value of engine heaters back in the 70s when I lived in Nebraska. I've used a Kat's tank heater on every carbed vehicle I have owned since then.

Some of the engine heaters are adhesive backed electric pads that you stick to the bottom of an oil pan or tranny or diff. Maybe there's one that can be wrapped around the bottom and sides of an intake manifold.

Again, I said, "What's YOUR installation (climate, etc.)? You have a Bronco, big grille, good airflow. That this is important has been shown over and over in the RV industry, which has lots of problems with engines installed in engine compartments with mediocre airflow, when the same engines don't have these problems in their usual installations in cars. My statement stands:D.
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I wasn't trying to correct your statement. :) Just giving personal account of how the the fuel mixture moving through the intake does indeed cool it down (which is why there's validity in heating the underside of the intake).


As for the engine heaters with the adhesive pads, that's actually what I looked into. It's the speed in which they heat up that's the problem. They're not designed for a quick rise in temp and are very gradual (which is why you leave them on over night). Unless they were left on, it'd be a while of driving before they heated the intake enough to be beneficial.

Do you have a "tank"-type engine heater (heats the engine coolant)? You're in Idaho; you probably know more about these things than I do. That would keep the coolant coil under your manifold warmed, wouldn't it?

Presumably you also have a good air-cleaner with the hot-air intake in the snorkel, yes? Guys who show their pretty rebuilt engines at the car shows don't like those big ugly black factory air-cleaners, and use the little round chrome ones instead. But I think that a modern factory air-cleaner housing (with a K&N filter) with the snorkel that takes in heated air, underhood air, or outside air depending on the situation is one of the best inventions in the history of automobiles.

And not only am I not trying to discourage anyone from adding a hot-spot under their manifold, the first thing I did to my plain, unheated Clifford single 4-bbl manifold was to fabricate and weld a set of coolant passages to the bottom of it. Just sayin' not everyone needs it, and I have a shutoff valve for mine. And an old Sears tank-heater.

See new post, "Wienie Roast Engine Heat" in this sub-forum. Here's another guy with the opposite problem.

With my headers, I had too much heat at the carburetor. It was causing all types of low-RPM driveability problems.

Do you think using the F600 manifold would heat the intake enough to not necessitate using coolant?

Yes it does for a single barrel carb ..

Why would it not for a four barrel?