Permatex 85420 vs Hylomar M on Copper head Gasket

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by Ray Hadford, May 27, 2018.

  1. Ray Hadford

    Ray Hadford New Member

    Mar 9, 2014
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    Has anyone tried Permatex PermaShield 85420 in place of Hylomar for sealing water and oil on an
    O ringed copper head gasket motor. Cooling system is on a supercharged SBC and is not pressurized..... Hylomar not available locally on a weekend. Permatex at one time purchased large batches of Hylomar and repackaged it for NAPA sale. Not sure if this is more of the same or a new formula by Permatex. Advance Auto Parts stocks the Permatex product.

    Ray H.
  2. TADHemiracer

    TADHemiracer Member

    Dec 9, 2010
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    I have had ZERO luck with Hylomar. However, I have excellent experiences with Permatex 'Ultra Gray'. Bonds to almost any clean surface, as much of an adhesive as a sealant which is a good thing. I threw four tubes of Hylomar in the trash. Good riddance. That said, I DO use a Dzus dimple tool to make a ripple around the oil return hole and an o-ring at the base of the oil passage block stud to head face to help seal the oil pressure to the head. Just another of my ignorant "country boy" techniques. I even removed the restrictors in the top of the block to send more oil to the rockers.....ZERO oil issues since. Just saying.

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