Chevy 305 in el camino sounds like boat motor

[weisel]

I was helping my brother fix his starter the other day and noticed that on his factory exhaust system, there is a weird vacume controled thingy on it. It lookes like a vacume controled diaphram moves a lever and spins a shaft in the tube which lookes like it has a throtle plate type thing in it. Try to imagine a vacume controled choke on the exhaust pipe! and it dosn't even have a hose hooked up to it. I just wanted to post this and see if any one has seen this, what is happening in it exactly, and what is it for?

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[muddin4fun]

Oh gawd! I know exactly what it is! I can't think if the name right now!!!!!! ARRRGGGG!!!!! The thingymagig, right!!!!! GRRRR!

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[weisel]

ya, the thingamajig...do you know what it dose?

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[muddin4fun]

heat riser valve!!!!!!!! I think? I dunno what it does. Prolly something when the motor is warming up.

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[BadDog]

I believe its only purpose is to block off exhaust on one side to force hot exhaust through the heat riser passage when the engine is cold.

Bad Dog

85 K30 CUCV, 350 TBI, TH400, NP205, D60/C14, 4.56 Locked
Soon: 4" lift, 40" tires, massive cutting, shorter wb and rear overhang.

 

[CaptCrunch]

I think baddog and mudd'n have nailed it! 2 points!

1987 Chevy K5 Blazer- 350 TBI

 

[Blazer79]

My Blazer had one of those. I couldn't believe it when I saw it. Fortunately it was stuck in the open position. I removed it and now I have a set of Flowtech Headers

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[weisel]

it dosn't get cold enough to need a heat riser here so i will just wire it open. thx a lot for the info.

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