In a message dated 96-10-04 00:41:49 EDT, you write:
<< When I rebuilt the engine for my '70 MkIII Spit I had the head surfaced.
Based
on the machine shops advice I did not use any type of compound with the
gasket,
however mine leaks an ever so small amount of oil at the left rear corner.
This leads me to believe that I should have used a gasket compound. Oh BTW
the deck of the block was surfaced too. >>
If the head and deck were milled, the problem may be the roughness of the
milled surface. A ground surface is much smoother, although depending on the
stone and operator, it may not be as flat overall. A milled surface CAN and
SHOULD be smooth... but it may require a rough and a finish cut -- which
takes the shop a bit more time, and hence is often not done. Some shops will
mill and then do a very fine grind, not removing much metal at all, but only
smoothing the high spots. You can also remove some of the roughness by
draw-filing the mating surfaces, which can be done carefully enough to
maintain the flatness. In fact, I've taken off .010 by this method, although
it was mainly out of poverty/cheapness rather than any other reason. If
you're interested, I'll write up the technique.
You may also lap the mating surfaces together to remove some of the
roughness. This can be done so well that you could run without a head
gasket, but unless you've got a good reason (heat transfer, desire to
increase compression a bit more without milling any more off the head or
block, etc.), it's not a good idea. A gasket adds a bit of resilience and is
much less likely to leak. Anyway, lapping can improve the surface enough
that a gasket will seal well.
In any event, check your flatness with a REALLY STRAIGHT and stiff
straightedge held absolutely perpendicular to the surface being checked. If
the straightedge is angled slightly and bends even microscopically, it will
not give you an accurate indication of the flatness of the surface.
Good luck !!
-Karl
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