This sounds like a cool way to get good information. As they say, seeing is believing. By the way, cool pic.

I see this topic has come up again and I couldn't help but chime in too. A lot of people seem to be focussed on keeping the intake manifold cool. All carbureted engines are designed to have a a warm intake manifold for the simple reason that only vaporized gasoline can be combusted.

If you are drag racing and need to squeeze the tiniest extra amount of horsepower of your engine, a cold intake will help. For street-driven engines, the hot-spot in the intake manifold is necessary for good drivability. Your engine will run best with the heat-riser (or manifold heat control valve) operating as it was designed.

That's what Chrysler seems to think. I have a 1964 factory service manual in front of me that lists "Manifold heat control valve stuck in heat-on position" as a possible cause for the following:

*Poor acceleration - hot
*Carburetor floods or leaks
*Poor performance - hot
*Poor idling - hot
*Excessive fuel consumption

And "Manifold heat control valve stuck in heat-off position" as a possible cause for the following:

*Poor acceleration - cold
*Poor idling - hot
*Excessive fuel consumption
*Poor performance - cold

Thank you for clarifiy this, I will immediately tell my engine to stop doing that.

But this is easy enough to test. Take a exhaust manifold and stick a hose into an intake port. Turn hose on. Close valve. Where does the water go? Open valve. Where does the water go? Remove valve. Where does the water go?

The same principles that govern the flow of water also govern the flow of exhaust gases.

What about convection of heat and turbulence?

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Only if you're talking about gaseous water and liquid exhaust. In the real world, where the water that comes out of a hose is a liquid and the exhaust that comes out of the cylinder head is a gas, well, the principles are different.
Let's turn your example on its ear: Point a garden hose straight at yourself and turn on the water. First your feet get wet, then your chest gets wet, as the water pressure increases. The water stays in more or less a single stream, cohesively pulled downward by gravity. The only way anything above the height of the (level) hose gets wet is by splash and splatter.

Now stand behind a car with a straight-out-the-back exhaust pipe and have someone start the engine. The exhaust pipe is at a height somewhere between your ankles and your knees, yet you can smell the exhaust (which means some of it's up at nose height!). How can that be? Must be because the exhaust goes out, down, up, left, right, and every which way, a plume rather than a single stream, not obviously subject to gravity.

Gimme a break, Kesteb, you're way smarter than "gas and liquid flow by the same principles".

Is the heat riser valve supposed to move when I rev up my engine. It is not froze up or anything, just runs bad in cold weather and great in hot weather. What I mean by "bad" is that it bogs on acceleration during cold weather no matter how far you drive it. Bog disappears in warm weather. Thinks it may be timing

By the way, how do you tell if it is closed or open?

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Yep.

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If it ain't broke, fix it!

Viewed from the front of the car, the clockwise position is "heat on", and the counterclockwise position is "heat off".

Nothin' but nothin' substitutes for Mopar 4318039AB manifold heat control valve solvent to free 'em up and keep 'em free.

So when I rev up my engine it switches to "heat off", right ?

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

FYI, the heat control solvent has been discontinued; it has been substituted for MP Penetrating Oil. Freeing heat control valves is listed as one of its uses, so I am assuming the formulation is the same, but the application has been broadened to boost sales. It worked very well for me.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Yeah, they're calling it "Rust Penetrant" now, but it still has that same funky "What's *in* this stuff??" smell, still has the same part number (in the US -- different PN in Canada) and still works the same.

Sorry Dan, Kesteb is right. Gas is treated as a fluid when describing flow through an enclosed system. There are differences in how both 'fluids' react to any changes within the system, which are dictated by both the fluid's and the system's properties. I.E Density, viscosity, velocity, pressure, and thermal conductivity. However, they still behave according to the same rules. The only real difference between a gas and a liquid in regards to flow is compressability. Gas can be compressed, liquids for the most part cannot.

Gasses and liquids have their differences, but the same flow principles apply to both.

...either way, with no flap the intake would get either wet or hot.

D/W

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If it ain't broke, fix it!

Sorry, Super6, no he ain't. We're not discussing theoretical fluid dynamics in a straight, round pipe here.
Well, yeah. Gas is one kind of fluid. Liquid is another kind of fluid.
Exactly. And the difference between a liquid and a gas is its density, so this is a fancy way of saying "Gases and liquids are two kinds of fluids which behave differently." You and I agree, as it seems.