How to Plug Smog Ports in Manifolds

Mopar Exhaust Systems

  1. DusterDaddy

    DusterDaddy sledgehammer mechanic FABO Gold Member

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    I want to use these manifolds in my Duster project and I need suggestions on how to plug the air ports.
    They are off a 75 360 Roadrunner. I know they are not A-Body manifolds, but others have used them on A's with minor grinding here and there.
    My 74 318 has stock 74 heads with a 1.88/1.6 valve job. They are ported and gently decked, and I am looking for decent flow through the manifolds.
    Any suggestions on plugging the air ports are welcome.
     

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  2. 70aarcuda

    70aarcuda Master Hoader of SBM FABO Gold Member

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    drill and/or tap with 1/4-20....get 1/4-20 set screws....

    alot of them are full of carbon and plugged already
     
  3. pishta

    pishta I know I'm right....

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    Hit them with a MIG welder and just load them up with wire. Grind smooth. A lot less work than tapping and screwing in pipe plugs.
     
  4. RustyRatRod

    RustyRatRod Weenie idiot loser. FABO Gold Member

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    NAPA used to sell some self tapping plugs that you threaded into the holes tight and then broke off flush. I don't know if they still do. Worth a try.
     
  5. Dartnut

    Dartnut Don't hate me because i'm beautiful

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    Why bother plugging them?
    If your heads don't have the ports, they are just along for the ride and will plug up with carbon anyway.
    If you want some more performance, just buy a set of cheap headers and fool with the fitment of them if you are willing to do some work. (And it sounds like you do)
     
  6. RustyRatRod

    RustyRatRod Weenie idiot loser. FABO Gold Member

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    If you run headers or manifolds that do not cover the ports, they have to be plugged.
     
  7. DusterDaddy

    DusterDaddy sledgehammer mechanic FABO Gold Member

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    The Manifolds I have need to be plugged. The heads on my motor do not have the air ports
     
  8. 70aarcuda

    70aarcuda Master Hoader of SBM FABO Gold Member

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    yeah....i thought you wanted to plug the heads....sorry...
     
  9. RustyRatRod

    RustyRatRod Weenie idiot loser. FABO Gold Member

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    Since they are so cheap, I would just advise you to get more mannyfolds.
     
  10. daredevil

    daredevil Well-Known Member

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    If the heads are plugged wont that block the manifold holes with the correct gasket.?
     
  11. daredevil

    daredevil Well-Known Member

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    I may not be right but wont those bolt flat against the heads and you need a 3/4 or 1/2 inch plug at the end of the manifold where the smog pump connects only?
     
  12. bighammer

    bighammer Well-Known Member

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    ^^ I think this may be the correct answer. Have you done a mock up to see how the manifolds will sit against the heads? When installed, I think maybe the holes you are concerned with will be blocked off by the head. Then all you need to do is put a plug in the end of the manifolds.
     
  13. DusterDaddy

    DusterDaddy sledgehammer mechanic FABO Gold Member

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    The correct answer was to be more careful about what I buy. The seller has not shipped these to me yet and has agreed to return my payment.

    Fabo members are the greatest. Saving my pennies for a set of 340 A-Body manifolds...

    Thanks for the responses
     
  14. 4spdragtop

    4spdragtop Well-Known Member

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    Probably gonna cost about 50 thousand pennies. Glad the seller refunded your $.
     
  15. DusterDaddy

    DusterDaddy sledgehammer mechanic FABO Gold Member

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    I have a good FABO pal who has a pair on layaway for 35000 cents
     
  16. alpha13

    alpha13 Well-Known Member

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    I would think that once tightened up to the heads the gasket would plug the hole then just tap the smog pump hole at the end of the manifold put a bolt on it with some locktite and then forget about it.
     
  17. gashaller

    gashaller Member

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    I have manifolds off 71 duster, on the pass side, where the flapper is it is leaking around the rod the goes through, what is the best way to permanently seal it?
     
  18. chryslerfat

    chryslerfat Well-Known Member

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    Knock the flapper out and wire weld the holes shut.
     
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