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. Thanks Ray H.