Can't get header to seal even with Percy gaskets

Discussion in 'Engine Topic' started by 81_Z28_NC, May 7, 2009.

  1. 81_Z28_NC

    81_Z28_NC Veteran Member

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    Aug 2, 2007
    thomasville,NC
    I have been wrestling the passenger side header (hedman elites...3/8" flange) on alum heads for a few days. I have changed the gasket 4 times and tightened the bolts several times (from center to end) and it seems like the entire top of the passenger side header just don't want to seal.

    First started with paper/cardboard gasket and they burned right through...then put on mr. gasket ultraseals (composite) and burned through 2 of them (one is on the driver's side and it seems fine). Being desprate I spent the $ on the recommended aluminum Percy seal-4-good dead soft aluminum ones and I can't get them to seal !!! This is getting rather annoying and expensive. Been recommended to try stock exhaust gaskets or the cardboard type but first soak in water overnight. These headers have less than 1000 miles on them and previously before removal it was sealed fine. I am guessing the flanges are warped or there is something up with the welded ends and them sealing...either way I was sure they woud seal up with the Percys. Any suggestions ? I am ready to tear these things off and replace them with exhaust manifolts. :screwup:
     
  2. hhott71

    hhott71 Veteran Member Lifetime Gold Member

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    Mar 30, 2001
    Joplin Mo. 64801
    Cut the flange so each tube is seperate if the flange plate is one piece.
     
  3. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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    Sep 20, 2004
    Southern Maryland
    are they hitting a casting on the head? It shouldn't be that hard to get them to seal. Don't put manifolds on there whatever you do!
     
  4. 80'427

    80'427 Veteran Member

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    Jan 1, 2005
    Fairbury, NE, USA
    I know noone will belive this but lately I have just used orange rtv snugged up the header to the head a bit, let it sit over night and tighten. Worked for the last 5 header jobs I have done.
     
  5. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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    Sep 20, 2004
    Southern Maryland
    orange rtv meaning the ultra copper? That stuff is pretty damn tough if you really really clean the mating surfaces well, I have done that on exhaust manifolds, just ultra copper, never tried it on headers
     
  6. 81_Z28_NC

    81_Z28_NC Veteran Member

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    Aug 2, 2007
    thomasville,NC
    I've heard that helps...thanks for the tip, I will keep that as a last resort.

    No they are not hitting the castings on the head. I know...should not be that hard to get them to seal, I don't know what's up with them. At least manifolds won't leak or burn up wires/boots...just frustrated. Going to take the gasket out when I get home from work to see what is up (for the 5th time)
     
    Last edited: May 7, 2009
  7. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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    Sep 20, 2004
    Southern Maryland
    I don't like the aluminum gaskets, they are very durable but not all that conformable.

    The Percys XXX graphite gaskets are cheap, and they are extremely soft, like felt, but made out of carbon fiber. They will fill in just about any gap. They are not at all reusable though, is the downside, they rip really bad when removed.
     
  8. SS2001

    SS2001 Veteran Member

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    Jan 4, 2008
    Lithia Springs, GA
    This is EXACTLY what I did on a Dodge 383 years ago after going thru the same thing! Ultra Copper RTV - put a heavy bead on, BARELY snug the bolts, then let set up. The RTV will form a solid rubber gasket that takes up any imperfections or slight warpage. Worked great.

    Another thing to check - make sure the headers are not hitting the lower a-frame mounts; if they are it will not let the header flange square up to the head.
     
    Last edited: May 7, 2009
  9. vegas1974z28

    vegas1974z28 Moderator Staff Member Lifetime Gold Member

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    Jan 10, 2002
    Las Vegas,NV

    Agree completely.
     
  10. Twisted_Metal

    Twisted_Metal Moderator Staff Member Lifetime Gold Member

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    Feb 26, 2004
    Bloomington, MN
    I used Hedman Elite headers (shorties) with Percy's gaskets. No problem at all.

    Those are heavy flanges... If they DO warp, they're gonna be a beech to seal.
    If that is the problem, cutting them might be the only way.
     

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