HP manifolds with NO gaskets (?)

Mopar Exhaust Systems

  1. bighammer

    bighammer Well-Known Member

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    My mechanic wants to machine my manifolds FLAT so that they can be installed with no gaskets. I've never heard of doing this, have any of you done it, with success? He says this is the best way of assuring no problems down the road.
     
  2. 66340SEDAN

    66340SEDAN FABO Member #3649 FABO Gold Member

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    Didn't some of MaMopars big block engines come without exhaust manifold gaskets when new? I thought I read an article one time about it....
     
  3. Leadfoot

    Leadfoot Author of The Primate Chronicles

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    Sure! But why? Gaskets last a long long time. If by chance they do fail, they're about fifteen bucks and an hour of your time.
     
  4. 4spdragtop

    4spdragtop FABO Gold Member FABO Gold Member

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    Sure, machine them, what would it hurt?? But I would still install the gaskets.
     
  5. Treblig

    Treblig FABO Gold Member FABO Gold Member

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    I wouldn't machine them unless they were warped bad enough to actually cause a leak. Even then, if they are warped real bad you would only want to machine off enough to get them to seal. The more material you remove the more likely they are to warp because they keep getting thinner and thinner. But you didn't mention what manifolds on what engine?? The old original manifolds tend to bend on the small ear areas because they're too thin from the factory. If you cut them down the ears will bend even easier. I really got tired of trying to get mine (stock factory manifolds, 318) to seal and finally went to the 360 magnum (super thick manifold) on the passenger side and the 340 driver's manifold (a little more heavy duty than 273/318). Haven't had a hint of a leak for years.... but like I said, you didn't mention what your working on??

    Treblig

     
  6. bighammer

    bighammer Well-Known Member

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    These are the HP 340 manifolds with the 2 1/4" outlets. They're going on my new LA 360.. They aren't warped, as far as I know, but they look pretty beefy enough to handle a resurfacing. The machinist is a highly regarded engine builder / race car owner and builder. I'm confident he won't do anything that would cause issues. I just haven't heard of going this route before.
     
  7. bighammer

    bighammer Well-Known Member

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    I DONT want to have to spend the time or risk breaking off a stud! BTDT! It was enough of a pita even while the engine was on a stand.
     
  8. doug 371

    doug 371 Well-Known Member

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    i never run gaskets on mopar manifolds
     
  9. Bad Sport

    Bad Sport HALF A BUBBLE OFF Staff Member FABO Gold Member

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    A lot of the cars came from the factory without them. When I pulled the original manifolds from my car there were none.
     
  10. Darter6

    Darter6 Well-Known Member

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    I've had more leaks with gaskets and IRON manifolds. Last car I've done,, No gaskets No leaks.
     
  11. Lelo Dart

    Lelo Dart *

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    Used a bead of ultra black around the sealing area on my headers (per directions) and they don't leak. No gaskets.
     
  12. d55dave

    d55dave Well-Known Member

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    Two perfectly machined flat surfaces will sit flat to each other and not leak. Add a gasket, especially with hot exhaust and expansion / contraction with heat cycles and you have a big potential for a gasket blow out and leak. Once there is a leak the hot exhaust gasses will actually erode the machined surfaces. To the best of my knowledge muscle era cars used no exhaust manifold gaskets. Gaskets on exhaust manifold a came into vogue more when aluminum heads became popular, and are included in gasket kits for older engine as a bandaid for warped and damaged surfaces.
     
  13. bighammer

    bighammer Well-Known Member

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    Interesting, thanks for the replies
     
  14. Mattax

    Mattax Just the facts, ma'am FABO Gold Member

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    No gasket needed on the 340 manifolds. Factory 'gasket' was the sheet metal heat shield whch few of us have or use. One side only IIRC.

    Look at the manifold mating surface, if you can still see some of the machine marks, then the finish is about as good as it was originally. Next check for flatness. If that's OK, then just bolt it up as shown in the FSM. Get the conical washers if you don't have them.

    Use a gasket on the outlet. Accurate and TTI both sell correct size gaskets (often hard to find locally). Accurate's has a metal ring - I personally like that.
     
  15. inertia

    inertia Well-Known Member

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    ^^^^ Xs2 . . lotsa cars came without gskts. between machined surfaces
     
  16. oldkimmer

    oldkimmer FABO Gold Member FABO Gold Member

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    ................I have never used gaskets between the head and ex manifolds on any of my v8 mopars..................kim..........
     
  17. pishta

    pishta I know I'm right....

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    motorhomes were the first I heard without gaskets, something to do with heat transfer but now Im reading many came without gaskets. Keep em flat and tight. Really, cardboard header gaskets?
     
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