4.3l exhaust manifold question and possible idea

Discussion in 'Performance & Fuel' started by a.graham52, Dec 26, 2012.

  1. a.graham52

    a.graham52 Rockstar 100 Posts

    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

    Attached Files:

  2. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    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. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    And, do you have sufficient room for the slightly larger manifolds?
  4. a.graham52

    a.graham52 Rockstar 100 Posts

    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. dobey

    dobey Epic Member 5+ Years 500 Posts

    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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