Exhaust manifold gaskets (using LA manifolds)

Discussion in 'Magnum Engine Swaps' started by dartslantsix, Jun 26, 2018.

  1. dartslantsix

    dartslantsix Well-Known Member

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    I am using '67 era 273 exhaust manifolds on my '94 Magnum. I used Magnum gaskets and they lasted about a year before blowing out. I know that there is a port mismatch between Magnum heads and LA manifolds.

    My question- What gaskets should I use? Magnum or LA or something for headers? I am planning on using Remflex gaskets.

    Remflex Exhaust Header Gasket Sets 6004 Magnum gaskets
    Remflex Exhaust Header Gasket Sets 6027 Pre-Magnum
    Remflex Exhaust Header Gasket Sets 6003 Headers
    Remflex Exhaust Header Gasket Sets 6016 LA with 5-bolt valve covers

    Thanks.
     
  2. dusted

    dusted Well-Known Member

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    I normally don’t run any gasket. Have the manifolds resurfaced and use a thin dab of ultra copper around the ports if needed.
     
    • Agree Agree x 1
    • DionR

      DionR Well-Known Member

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      Wow, a month late on this. Hope it isn't completely useless.

      I think you just need a good 318 or Magnum gasket.

      My understanding is the mismatch between LA and Magnum ports only comes into play when using 340/360 manifolds (and headers?) on a head with reduced material under the port (EQ or MP R/T, for example). Best I could tell, the Magnum port is a match to the 271/318 port, and on the OEM heads a buddy of mine had, the 340 manifolds I have would have been fine as the sealing face went all the way down to the deck. But on my MP R/T heads, the head is undercut below the port leaving not enough material to seal the manifold.

      Because of this I had to build adapter plates that had the port from the Magnum on the inside and the outside matched the outside of the manifold. These started leaking and then leaked immediately the second time I used them (although that could have been installer error, too).

      I have planned to go to a smaller port header someday to get rid of the adapters, but haven't gotten that far.

      Either way, I kind of doubt the issue you have is due to a port mismatch.
       
    • dartslantsix

      dartslantsix Well-Known Member

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      Thanks for the response. I replaced the gasket with a remflex... but my problem was actually the pipe to manifold joint. Ugh. Replaced the nuts with lock nuts and we're all good now.
      This is good info for future searching.