Exhaust manifold flapper?

[hevymetl]

Was tracking down an exhaust leak today and noticed what looks like some kind of flapper or clapper valve at the base of the exhaust manifold. It appears to have some sort of spring or thermo control thats involved. What is this and is it needed? The spring mechanism isnt operative on mine. Should it be in a specific position for my motor to run its best? Its a 66 long bed, 2wd, c10, with a 250 I6. 4spd on floor.

[jjzepplin]

I had one of those on my Blazer on a V8 only one side though. It appeared to be some sort of choke type device to warm the engine up faster. Mine was stuck closed and choked the engine from running good so I just took it out and bam. No more exhaust leak and it ran much better.

[LT1 Burb]

They sell the piece sans the flapper.

[hevymetl]

The exhaust leak is right at the first clamp so it doesnt actually involve the flapper. Im thinking is that if I can just figure out which position is "open", Ill just fix it so it doesnt move.

[Backpayne]

It is a heat riser. It allows the carb to warm up to improve atomization of the fuel.

[jtrichard]

BEST thing to do with it is remove it and cut the FLAP out BUT leave the shaft REINSTALL with new gaskets

[hevymetl]

Im gonna have to soak the crap out of it. Its all rusted pretty good.

[Metalaroundstone]

Originally Posted by hevymetl

Im gonna have to soak the crap out of it. Its all rusted pretty good.

Since you live where the weather gets cold, this heat riser valve can be helpful in warming your engine on start ups. A bi-metalic spring does the work of closing the valve when the engine is cold and opening the valve as the engine heats up-- that is as long as it moves freely. You can buy a new one, but they are on the expensive side, like around $50-$60. Mine was in a similar condition, but I managed to get it operable again with a little work.

Here is another thread on the subject http://67-72chevytrucks.com/vboard/s...d.php?t=313227

[jdl71]

You can buy a complete new manifold, with heat riser for $140.

https://www.summitracing.com/parts/a...make/chevrolet