what is the valve in the exhaust

[dave jensen]

can anyone tell me what that valve is in the exhaust. it is located on the passenger side on a 79 chief with a 360. mine rattles like crazy, and it is not connected to anything.
thanks
dave

[Don S]

dave jensen ......That is a valve that forces exhaust up to the intke manufold To help warm the engine and help control the automatic choke. And it does a few other things..Its called a heat riser...Make sure it works freely and not stuck in the closed possition........ds..

[JEEPGUZZZI]

That is an emissions control device called a heat riser. It restricts the exhaust flow until your motor warms up, causing a bi-metal spring to expand and open the valve thru a weight on the outside.

[dave jensen]

how do i make it work correctly
thanks
dave

[Don S]

dave jensen ...... I used to put a small amount of high temp oil like 2cycle outboard oil shaft and tap the shaft lightly with a small brass hammer to free them up... But years ago I cut the valve out and installed a hand choke. Next I'd like to install a hand controlled spark advance...You know all the good cars used to come equiped with these neat devices.. :eek: ......ds..

[Crazy_Jeepman]

If it rattles like crazy most likely the bi-metal spring is broke or gone. Then you will need to replace it, or as I do get rid of it. This valve is is only to get hot air up to the air cleaner for cold starts. It gets the right exhaust manifold hotter quicker and the heat riser shroud on that manifold directs the hot radiant air through the foil hose to the air cleaner to prevent carb icing up in cold weather starts. I remove the butterfly valve out of them and put it back on, no more rattles! ;)

[xj2fsj]

coincidently, I recently removed mine and while cleaning it, I broke it in two. I was planning on reinstalling it since I live in minnesota and cold mornings are a way of life here. I was forced to put my exaust back together without it and it was a b*tch to fit it together without that 1" peice of cast iron. Now it leaks no matter how tight i torque the studs. anyone know where to get one?

[Don S]

Crazy_Jeepman .....That covers it pretty good but may I also add for some who didn't know....When the valve is closed some of the righthand exhaust is is forced through the intake manifold and goes out the left exhaust system thus heating the hole intake manifold for quicker "rapid fuel Vaporization during engine warmup".....
;) ....ds..

[LRRH]

you should be able to find them at most parts stores...cause they were fairly similar across all years. they're kinda expensive and usually run about $50.........

[64Trvlr]

<blockquote>quote:</font><hr>Originally posted by JEEPGUZZZI:
That is an emissions control device called a heat riser. It restricts the exhaust flow until your motor warms up, causing a bi-metal spring to expand and open the valve thru a weight on the outside.<hr></blockquote>

It is not any sort of emissions device at all. All it does is port exhaust gas from the right side throught the underside of the intake manifold and out the left side exhaust. It helps on cold starts and for cold drivability. I put one on mine when I built the exhaust system. You can get a replacement from NAPA, Carquest, ect if you want to replace it. Or just find a nonfunctional one at a muffler shop and remove the valve from it and put it in.
:cool:

[Crazy_Jeepman]

I believe I have a good one if any of you need one, email me, then I will check. ;)

[JEEPGUZZZI]

I would disagree, trveller. The device was put on to help driveability on lean-tuned emissions vehicles to speed warm ups, reducing time on fast idle, and thereby reducing emissions. I think if you ask any of the EPA police, they will tell you that it is part of the emissions package and if it isn't there, you wouldn't pass a visual inspection. :(

[JEEPGUZZZI]

Also, every one that I have removed has been cracked or completely broken in two. :rolleyes: :rolleyes: :mad:

[Crazy_Jeepman]

I doubt it is an emisions device, pre smog vehicles used them, and not all smog vehicles have them. My 70 has it and I beleive my 67 has it as well. However a muffler clamp could be classified as part of the emissions system, so who knows. They do usually crack and fall apart, but I have 1 that is good and one I cut the butterfly out of to bypass it. ;)

[64Trvlr]

<blockquote>quote:</font><hr>Originally posted by JEEPGUZZZI:
I would disagree, trveller. The device was put on to help driveability on lean-tuned emissions vehicles to speed warm ups, reducing time on fast idle, and thereby reducing emissions. <hr></blockquote>

I'll disagree with that statement as they have been installing them since the 50's. And that was long before anyone ever thought or cared about emissions. They do help as you said but that was not the origional purpose for them.
:cool:

[JEEPGUZZZI]

Ahh, there's the problem,,,I am not old enough to have had a car from the '50's :D :D tongue.gif tongue.gif

[Lugnut]

Okay. Enough, already! This ol' f*rt says it's only used to create a little back-pressure on the engine so it will warm up faster; thus the bi-metal spring. You will notice that when you rev the engine cold the butterfly still opens but not as easily as when the butterfly spring has heated up. The spring warms up, relaxes it's tension, the butterfly stays open when accelerating or at highway speeds (or really anything much above an idle.
The back-pressure created by this exhaust damper, at idle, after it has warmed up, is not significant; will not be harmful to an engine. But, as was mentioned, you do need to make sure it's functioning properly, that is, opening/closing with acceleration/deceleration.
True, many people disable them or do away with them entirely because of leaks, rattles or rusting shut.
AND, heck, they been usin' 'em since the 40's.

[64Trvlr]

<blockquote>quote:</font><hr>Originally posted by Lugnut:
Okay. Enough, already! <hr></blockquote>

ROTFLMAO
And your point?
:cool:

[79 FSJ]

I have had a very weird stumble in the middle of my acceleration that we can not track down... not ignition, not timing, not carb... etc... and I also have a presure release throught the carb that resembles a back-fire but it is not... could maybe this exhaust valve be causeing this???

thanks
Dave