Slant Six Forum :: exhaust manifold heat riser

Okay getting back to the riser topic

At whatever times the flapper is opened to the max, it looks to me like the dead space created changes the heat from forced air to radiated. In the meantime theres ambient air pouring in through the carb.

Woiuldn't that actually srve to cool the manifold floor slightly, therefore slightly condensing the intake charge to enhance power?

If true, then a high load situation would tend to magnify this effect?

Man did I ever ask the wrong question. I never in a million years ever thought I would stir up this much emotion about anything. I only removed it because it was frozen up and I couldn't unfreeze it.

...but to call someone dumb or retarded for trying, is just down right cruel and insensitive.

Dude. Read carefully. No one called you or anyone else retarded.

At whatever times the flapper is opened to the max, it looks to me like the dead space created changes the heat from forced air to radiated. In the meantime theres ambient air pouring in through the carb.

Woiuldn't that actually srve to cool the manifold floor slightly, therefore slightly condensing the intake charge to enhance power

I have other questions, but I think I'll keep them to myself for right now or just search the board for previously asked questions.

... I have other questions, but I think I'll keep them to myself for right now ....

I have other questions, but I think I'll keep them to myself for right now or just search the board for previously asked questions.

yeah so I'm rebuilding my front end have always used poly on my 4wd trucks... MJ

yeah so I'm rebuilding my front end have always used poly on my 4wd trucks...even the ones with with IFS!<===========) MJ

Author:	440_Magnum [ Wed Apr 06, 2005 10:24 am ]
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Quote: Okay getting back to the riser topic At whatever times the flapper is opened to the max, it looks to me like the dead space created changes the heat from forced air to radiated. In the meantime theres ambient air pouring in through the carb. Woiuldn't that actually srve to cool the manifold floor slightly, therefore slightly condensing the intake charge to enhance power? If true, then a high load situation would tend to magnify this effect? You're right that when the valve is in the "no heat" position, there is STILL radiated heat and conducted heat because the intake and exhaust are bolted together on an sl6. Even on a v8 with the flapper in the "no heat" position, there is still random shuttling of exhaust gas through the intake crossover passage because the pressures on both banks are never precisely equal. This residual heat serves to keep the incoming air and evaporating fuel from getting so cool that the fuel doesn't vaporize properly. Will the manifold "cool down?" No. Its warmed by radiated heat, but remember that the exhaust is over 1000 degrees F! That is a LOT more heating potential than there is cooling potential from intake air and fuel. Will high-load magnify the effect? Not really. Yes, more cool air comes in and more fuel absorbs its latent heat of vaporization, adding to the cooling, but under load both the volume and temperature of the exhaust gas shoots way up as well. If you run an engine all-out on the dyno, even a tame sl6, the exhaust manifold will eventually glow dull red. A race engine will make it bright yellow. You just can't overcome that kind of heat with room-temperature intake air.

Author:	Dennis Weaver [ Wed Apr 06, 2005 10:32 am ]
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Quote: Man did I ever ask the wrong question. I never in a million years ever thought I would stir up this much emotion about anything. I only removed it because it was frozen up and I couldn't unfreeze it. So, in essence, there is no claimed advantage, only potential disadvantages. Nobody said you commited a crime, if I remember, you asked if your slant would run better with a properly working valve, and I think that's been answered, albiet with a few dissenters. D/W

Author:	Dennis Weaver [ Wed Apr 06, 2005 10:38 am ]
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Quote: ...but to call someone dumb or retarded for trying, is just down right cruel and insensitive. Dude. Read carefully. No one called you or anyone else retarded. I think my exact quote was "removing the flapper valve seems retarded to me", meaning the act or removing the valve seems to me to be "retarded", which it does. That's very different than saying "ole_blue, you are a retard!" D/W

Author:	NewLancerMan [ Wed Apr 06, 2005 12:22 pm ]
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Quote: Dude. Read carefully. No one called you or anyone else retarded. Sorry ole, dennis reserves that title for me exclusively. I like to ask him the same question over and over until he has no recourse other than to slap me around

Author:	argentina-slantsixer [ Wed Apr 06, 2005 2:07 pm ]
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he, I dunno with the intake, but the heat riser worked perfectly on this forum. we got dull red, bright yellow, etc etc My car likes to put headers red when I do a lot of WOTting. I even melted a piece of 1/2" thick cable (my battery cable) at the highway, one day I got into a "speeding" contest with a piece of rice. No need to say I kick his sorry ass... I parked and did a few errands and when I was about to go again, "click" "click" (starter relay) but nuttin. The ex melted down completely that cable. No fire or troubles whatsoever other than having to replace the cable.

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exhaust manifold heat riser https://slantsix.org/forum/viewtopic.php?t=12454	Page 7 of 8

Author:	FrankRaso [ Wed Apr 06, 2005 5:42 pm ]
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kenG wrote: Quote: At whatever times the flapper is opened to the max, it looks to me like the dead space created changes the heat from forced air to radiated. In the meantime theres ambient air pouring in through the carb. Woiuldn't that actually srve to cool the manifold floor slightly, therefore slightly condensing the intake charge to enhance power I think it would be helpful to look at the operation of the intake manifold slightly differently. The air in the intake manifold is continuously being cooled by the evaporation the fuel. If the manifold was not heated and no heat were added to it by a heat riser, the intake manifold would get very cold. Depending upon the ambient temperature, it could possibly reach a temperature where the fuel would mainly puddle on the plenum floor. The intake needs to be heated to replace the heat absorbed by the evaporation of the fuel. When an engine needs to be warm to run well, the engine runs well because the intake manifold is warm, even too hot to touch. At low engine speeds and high manifold vacuum, the hot spot in the intake manifold causes any drops of fuel that haven't evaporated to evaporate. Liquid fuel puddled on the plenum floor prevents the cylinders from getting a good distribution of fuel. At higher engine speeds and low manifold vacuum, the engine depends upon good atomization in the carburetor and good intake design to get the fuel distributed evenly to the cylinders. When the air flow through the intake manifold is high, the intake manifold hot spot has a minimal effect on heating the air reaching the cylinders so the engine is able to produce more power with the cooler and denser air. People often focus on having a cold manifold because they want to maximize the power of their engine. The focus should be on ensuring that all cylinders receive an even distribution of the proper fuel mixture. Frank

Author:	ole_blue [ Thu Apr 07, 2005 1:09 am ]
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To heat rise or not to heat rise, that was the main question. It seems this is a matter of opinion and personal experience, which now I have both. I think I will seek out a manifold with a working heat riser and install it. Thanks for all the advise and working knowledge of the heat riser. I have other questions, but I think I'll keep them to myself for right now or just search the board for previously asked questions.

Author:	Charrlie_S [ Thu Apr 07, 2005 6:33 am ]
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Quote: I have other questions, but I think I'll keep them to myself for right now or just search the board for previously asked questions. Hey, don't chicken out, now.

Author:	argentina-slantsixer [ Thu Apr 07, 2005 7:21 am ]
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Quote: ... I have other questions, but I think I'll keep them to myself for right now .... Oh my...! for the board members sake, shoot your questions and buckle up, or we may just start to waste money on shrink...

Author:	Dennis Weaver [ Thu Apr 07, 2005 7:38 am ]
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Quote: I have other questions, but I think I'll keep them to myself for right now or just search the board for previously asked questions. As long as they don't involve "poly" suspension or MSD ignition, you are safe! D/W

Author:	NewLancerMan [ Thu Apr 07, 2005 8:17 am ]
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Quote: As long as they don't involve "poly" suspension or MSD ignition, you are safe! [/quote] yeah so I'm rebuilding my front end have always used poly on my 4wd trucks... MJ

Author:	Dennis Weaver [ Thu Apr 07, 2005 8:33 am ]
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Quote: yeah so I'm rebuilding my front end have always used poly on my 4wd trucks... MJ You'll be glad to know, MJ, that it is a universally accepted fact that "poly" werkz great on leaf spring suspensions! D/W

Author:	NewLancerMan [ Thu Apr 07, 2005 8:34 am ]
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Quote: yeah so I'm rebuilding my front end have always used poly on my 4wd trucks...even the ones with with IFS!<===========) MJ hmm somehow forgot to finish my thought! So there =)

Author:	Rob Simmons [ Thu Apr 07, 2005 11:08 am ]
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From breathers to heat risers.....

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Author:	Dennis Weaver [ Thu Apr 07, 2005 11:17 am ]
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MJ, Pop pop! D/W