15 thou isn't tight - if you checked them cold it is correct, if hot then
loose - it should be 13.
The rocker cover nuts tighten down to a shoulder, not the gasket and the
head, to prevent the cover being distorted by too much pressure. There are
two rubber washers under the domed caps under the nuts and it is only how
much these are compressed that puts pressure on the gasket. They harden
over time and often when disturbed, even with a new gasket, you cannot get a
seal, until these are replaced as well. Having said that either the washers
and/or the gaskets currently available aren't as thick as they should be
because with both replaced my cover still leaked until I shimmed out the
rubber washers with a couple of thicknesses of gasket card.
PaulH.
----- Original Message -----
> ... I have adjusted the valves ( a
> couple were tight at 15thou).
> ... I never seem to be able to get a
> good seal between rocker cover and the head.
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