12-06-2013, 01:03 PM
(12-04-2013, 10:26 PM)The ferret_imp Wrote: Back in 1979 and thru the 80s when the dohc Honda 4s came out, they had the exact same set up we have now, in that the valve cover was one big piece ( kinda of looked like an H) and there was a large rubber gasket that went in little groove around the whole cylinder head between the head and the cyl head cover. It was imperative that the gasket be clean and that ( going by memory here) that a light layer of silicone be put in the groove on the cylinder head before installing the gasket to hold the gasket in alignment and prevent a leak. The slightest twist or misalignment of the gasket, or a thin spot in the silicone would allow a small leak there under pressure. As these gaskets got older, they stretched from the heat and became increasingly difficult to keep in the groove, and at this point the rubber gasket was usually replaced with a new one.
For what it's worth, rubber actually shrinks when heated !