Ok these are my experiences with exhaust and intake manifold heat.
yes the intake needs heat to vaporize the fuel, but heat riser or not the intake manifold WILL get hot. cast iron conducts heat very well.
Since going to headers(no direct intake heat) my intake manifold gets to hot to touch in the summer just due to radiant heat from the header pipes being in close proximity to the intake.
In the winter I run my heatercore supply hose to copper pipe attached to the bottom of the intake manifold where the riser would supply heat. The hose then continues to the heatercore. I also take the open element off and reinstall the stock super six aircleaner and heated air intake tube attached to the headers. between these two "heat sources" my intake manifold still gets too hot to touch.
my 2 cents
P.S. lets not go back to insulting and name calling peoples questions or ideas

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Certainly not. Remember, there's such a thing as right/correct/good information and such a thing as wrong/incorrect/bad information, and the latter kind just isn't as warm, fuzzy and lovable as the former kind. Letting the board de-evolve into a BS "All opinions on how things work are equally valid, no matter how incorrect they are" cesspool would be a bad thing. The generally high quality of the info is what sets this board apart from others. I try to hold the insults and namecalling to a bare minimum -- and I'll admit, sometimes I succeed better than other times at this -- but if someone posts something that's flatly wrong, I *am* going to call 'em on it. And others are completely free to do the same to me if I post wrong info.

Now, just to beat this dead horsey a *leeeeeetle* bit longer:

If you pee very carefully in a toilet, it won't get in your face or anyone else's unless you are doing something very wierd. If you sit on the very same toilet and blast out a huge bean burrito fart, it gets in the face of just about everyone in the house.


Liquid. Gas. Two different kinds of fluid. Two different kinds of behaviour.

Let me ask you this...

Wouldnt a hunk of metal(heat riser)in the middle of a exhaust system with heat blarring on it all day eventually get red hot.Thus creating severe heat to the carb issues,instead of just free flowing exhaust running through the exhaust manifold?

By the way I yanked my heat riser out over 2yrs ago because of a nasty exhaust leak through it and have never had any bad running issues.Yes it takes a couple more minutes to warm up but thats it.I kind of look at it as free flowing exhaust.

Dan I am not saying you are wrong though.........
Just kind of where I am with my car right now.

I am sure this debate will go on as long as the /6 is around.


JZ

No.

You are probably right that the manifold heat control valve (flapper) would get red hot from being exposed to hot exhaust gases. In the fully hot position, it is deflecting the hot gases from hitting the bottom of the intake manifold.

It is the exhaust gases that are hot. The flapper gets heated by the gases and there is no way for it to cause heat. Think of it as a heat shield for the intake manifold. Your engine will (obviously) run with the flapper removed but it will not run optimally.

In the closed (fully hot) position, the valve smooths the flow through the exhaust manifold and reduces its turbulence. Reducing turbulence makes the exhaust more free-flowing.

In order for a piece of metal to become red hot it needs to be heated sufficiently to bring it to the temperature at which it becomes luminescent. Due to the large manifold and the heat transfer to it, the valve does not become red hot. Unless the engine is loaded heavily with a very lean mixture, the flowing gases will never heat the valve to this degree. It is a moot point.

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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.

For the life of me, I can't understand why anyone would want to take the valve out. Fix it in the "no heat" position, maybe, but take it out seems dumb on several counts.

D/W

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If it ain't broke, fix it!

The ignorance in this thread is, frankly, appalling.

In a nutshell, Dan's right, you're wrong.

The LONG story is this: the heat riser valve on a slant six DOESN'T WORK the same way it does on a 318, 340, 383, 440, or even a Hemi. On all those engines, the flapper diverts hot gas TO a location where it will heat the intake. On a slant-six, the flapper diverts hot gas AWAY from the bottom of the intake and gives it a smooth path straight out the exhaust pipe. See the difference?

Therefore:

Removing the flapper on a Mopar V8 will reduce manifold heating, and is OK to do in warm climates.

But removing the flapper on a slant-6 will cause FULL TIME FULL-BORE manifold heat. Hello vapor lock! Hello warped carburetor flanges! "Hmm, it sure does KNOCK if I don't retard the timing way back, gee I wonder WHY?" Goodbye horspower, goodbye reliability.

I swear some people must not even LOOK at how a thing works before pontificating on it.

DING DING DING!!!


Holy crap this newb's coming out of the ropes swinging!

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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, I feel kinda bad about that, so I tried to be a little more helpful in another thread. What happend was that I got one of those "you won't BELIEVE..." e-mails pointing me to this thread and the silliness therein, and I just couldn't keep my mouth shut after reading for a while. I mean we'e talking about one of the basic Truths of Mopar here "the slant-6 heat riser valve works backward to all the v8 heat riser valves." The word according to Walter P.....

I wish I were a little more of a "newb" in the real world.... I've been tinkering with Mopars since the mid 70s. I was "slacker" on the old Mopar Mailing List back in the early 90s, and I still hang around rec.autos.tech. I'm far from a slant-6 expert- I own 5 B/RB engines (3 440s and 2 383s), a 3.5L v6, a '49 217 flathead six, and a 318- but I've had enough slanted engines to know which way the riser valve works.

Good way to put it, and welcome to the site!

D/W

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If it ain't broke, fix it!

i must be an anomoly, cause I don't have any problems with vaper lock, knock, poor reliability etc. Never a fuel related problem. The only time my slant let me down is when a coil went out. Sorry to spoil your fun gang, but these "ill effects" you talk about just arn't there for me. But, what do I know.

so is smartassing....

who's to say what's correct and what's wrong? we're not talking about a specific criteria... seems to me that there's some people willing to bend any theory to their side of the field. If you go theoretical then you can't just use a fart and pee to level the ground if you don't like what others have posted about the same subject.

And what about the flapper shape itself? no one has brought that to lite, not even the "people that makes this site great posting rite info". Flapper axis is eccentric. When it closes, it closes the way about 75% of the open space. So "the fart" may get thru that remaining 25%. And, if the gas-fart molecules are so retarded to go all over the place, why the flapper needs to be diverting the flow with larger area interfering the ex flow? if they're so dumb to go all over the place the flpper might as well be centered over its axis. But no.

So to me is clear, no one can predict how exactly a motor is gonna behave, especially not being familiar with that particular engine and its surrounding enviroment, and kinda mill, type of duty, etc etc etc.

There's one thing that's called theory, and other thing that's called real life. In theory you have to bear with theoretical elements, in real life with huge bean burrito farts. Those things ain't mix together. They only mix together if you're close minded enough to try to be right no matter what.

love to everybody. Juan

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

I beg to differ. We ARE talking about a specific criteria- namely what happens when you remove the heat riser flapper in a Chrysler slant-6 engine. This isn't a debate on the merits of which wine should go with fish, this is engineering. Within limits (which are WELL beyond this topic) you CAN predict exactly how a motor is going to behave- how else do you think NASCAR and IRL engine builders turn out hundreds of engines each year and build batches of them that differ by no more than 2 horsepower despite being built by different pairs of hands inside the shop? How do you think they go in to a race week and set them up for maximum horsepower based on the weather forecast for race day? For that matter, how do you think Detroit builds millions of engines that all meet spec, despite relatively lax assembly-line engine building methods? When it comes to engineering, what you are dismissing as "theory" IS real life. I'm not saying that we understand *everything* that goes on in engines- the actual combustion dynamics are very complex and take supercomputers to model completely (and even then approximations occur). But even there, the engineers know a whole lot and can set parameters about chamber shape, spark-plug placement, ring pack height, etc. and make PREDICTABLE changes to performance and emissions. But ferpete's sake, we're talking about how the intake manifold heat control device works here!! Talk about something that is well-understood, its right up there with 2+2=4.

Say what, Juan? That "open space" is a turbulent dead-end to nowhere! Why is is so important to some of you that the exhaust just have a big empty space to flow into and swirl around, heating issue aside? I'm sorry if I'm offending some of my pals here, I am as guilty of an occasional brain-fart as any, but this one is quite clear - to pull the flap out on a slant six is dumb.

Love,
D/W

AFTERTHOUGHT: Those of you on the "other side" of this supposed issue keep insisting that the disadvantages spelled out are not true. Please assert some actual advantages you realize by deleting the valve.

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If it ain't broke, fix it!