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  1. #1
    Jr. Engineer
    Join Date
    Aug 2010
    eas' bum fuk, maine

    Default 4.3l exhaust manifold question and possible idea

    so i got looking at pictures of my old 1985 gmc sierra with a carbed 4.3l and i noticed the exhaust manifolds look a hell of a lot nicer flowing then whats on my 01 4.3l. what do you guys think the chances are of swappin them over and getting any gain from them? obviously the head pipes on my 01 will need to be reworked but thats minor.

    compare the two pics
    Click image for larger version. 

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    "i dont think you got the picture. i got a beautiful picture. this baby happens to have an extra turn of speed, which is the only thing i care about. you dont understnad what happens do you? they make cars. they make 'em exactly the same way. one or two of 'em turn out to be something special. nobody knows why. i know why. i may be kiddin' myself, but i think i can make somethin' out of that sad little bucket of bolts." ~ Tennessee Steinmetz

  2. #2


    You really need to check the ports to ensure they match up.
    A little die makers blueing will give you an idea of how close they are. You might have to do a little porting to get a good flow.

  3. #3


    And, do you have sufficient room for the slightly larger manifolds?

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  4. #4
    Jr. Engineer
    Join Date
    Aug 2010
    eas' bum fuk, maine


    ill have to look and guestamate. i dont have the old style manifolds (they went with the truck) nor do i have a head i could test fit with either.

  5. #5


    I'd say the newer ones on the newer truck flow better. The fact that the older ones are longer may be deceiving you into thinking they flow better, because they are longer. The 90 degree bends will create some restriction. If you want better flowing exhaust manifolds for your newer truck, why not just buy a set of headers that are made to fit it, rather than trying to rig up manfiolds for an older version of the 4.3, which probably flow worse anyway?

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