Slant Six Forum :: exhaust manifold heat riser

The intake never "becomes quite cool to the touch" when the engine is running -- it only ever gets warmer. It'll get warmer faster or slower, depending on ambient temperature and operational state of the heat riser, but it will never "become quite cool to the touch".

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

Is the heat riser valve supposed to move when I rev up my engine.

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

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.

Quote:

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

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

Sorry Dan, Kesteb is right.

Gas is treated as a fluid

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.

Author:	ole_blue [ Fri Apr 01, 2005 9:45 am ]
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This sounds like a cool way to get good information. As they say, seeing is believing. By the way, cool pic.

Author:	FrankRaso [ Fri Apr 01, 2005 10:04 am ]
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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.

Author:	SlantSixDan [ Fri Apr 01, 2005 10:33 am ]
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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

Author:	kesteb [ Fri Apr 01, 2005 2:17 pm ]
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Quote: The intake never "becomes quite cool to the touch" when the engine is running -- it only ever gets warmer. It'll get warmer faster or slower, depending on ambient temperature and operational state of the heat riser, but it will never "become quite cool to the touch". 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.

Author:	steponmebbbboom [ Fri Apr 01, 2005 2:22 pm ]
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What about convection of heat and turbulence?

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Author:	SlantSixDan [ Fri Apr 01, 2005 2:31 pm ]
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Quote: The same principles that govern the flow of water also govern the flow of exhaust gases. 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".

Author:	Jeb [ Fri Apr 01, 2005 8:16 pm ]
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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?

Author:	Dennis Weaver [ Fri Apr 01, 2005 8:32 pm ]
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Quote: Is the heat riser valve supposed to move when I rev up my engine. Yep.

Author:	SlantSixDan [ Fri Apr 01, 2005 8:44 pm ]
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Quote: By the way, how do you tell if it is closed or open? 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.

Author:	Jeb [ Fri Apr 01, 2005 8:52 pm ]
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So when I rev up my engine it switches to "heat off", right ?

Author:	steponmebbbboom [ Sat Apr 02, 2005 11:12 am ]
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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.

Author:	SlantSixDan [ Sat Apr 02, 2005 11:18 am ]
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Quote: 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. 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.

Author:	Super6 [ Sat Apr 02, 2005 4:23 pm ]
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Quote: Quote: The same principles that govern the flow of water also govern the flow of exhaust gases. Gimme a break, Kesteb, you're way smarter than "gas and liquid flow by the same principles". 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.

Author:	Dennis Weaver [ Sat Apr 02, 2005 4:31 pm ]
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...either way, with no flap the intake would get either wet or hot. D/W

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Author:	SlantSixDan [ Sat Apr 02, 2005 5:09 pm ]
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Quote: Sorry Dan, Kesteb is right. Sorry, Super6, no he ain't. We're not discussing theoretical fluid dynamics in a straight, round pipe here. Quote: Gas is treated as a fluid Well, yeah. Gas is one kind of fluid. Liquid is another kind of fluid. Quote: 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. 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.