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swapping caddy heads?? help

Discussion in 'The Hokey Ass Message Board' started by hellspawn, May 26, 2009.

  1. hellspawn
    Joined: Aug 11, 2004
    Posts: 119

    hellspawn
    Member
    from Wayne Pa

    I know that swapping 390 caddy heads and intake onto a caddy 331 is pretty much bolt on...but is there anything else that has to be done? new valves,etc.
    has anyone here done this?
    does it make a noticeable difference?
    any help is much appreciated
     
  2. Marko
    Joined: Jan 27, 2005
    Posts: 156

    Marko
    Member

    The 390 has larger valves, they are farther apart c/l-c/l then the 331, so i think you need longer pushrods ( probaby 390 spec ). I have a set of 1960 390 heads, and although the center exhaust ports are still siameze ( sp?), there is a cast-in devider that helps direct the flow out. There are quite a few tech articles if you search for it. The intakes all interchange, so I think other then pushrods, it's a simple swap, but I'm a newby with Cad mills. Good luck.
    Marko
     
  3. HEATHEN
    Joined: Nov 22, 2005
    Posts: 8,974

    HEATHEN
    Member
    from SIDNEY, NY

    There is a large difference in exhaust port size from the earliest to the latest heads, so your current exhaust manifolds may not work.
     
  4. With the smaller bore of the 331 you may have a sharp edge protuding into the larger size head combustion chamber. Get the 390 head gasket and place it on your block to check this. This was one of the reasons I bored my 331 block as far as I could to match up the bore with its new chamber size. Mismatch can create a turbulance on compression stroke that could lead to uneven fuel burn. Also use the intake gasket to check ports on intake manifold, you can trace port size and grind ports to match head ports. You must use the 390 exhaust manifolds.
     
    Last edited: May 27, 2009
    ls1yj likes this.

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