I've seen over 225 psi on my race TR-4 motor. Seems I had close to
250 on at least one cylinder. Head gaskets aren't a problem for me
(since I quit using the shim and copper ones, anyway), although I go
maybe 1000 (very hard) miles between rebuilds. Liner protrusion is
key. You need a few thou (say 2 to 4 thou), but not too much. You
can adjust this to a point by making custom figure 8 gaskets out of
proper thickness shim stock. Can be carefully done with
scissors. They should be reasonably flat, although I have a thou or
two difference between the lifter side of the block and the opposite
side. The stock (Payen AE-330) composite gasket handles this
fine. I highly recommend Payen over the slightly cheaper stuff
available. ALL LINERS SHOULD HAVE VERY SIMILAR PROTRUSION - any
differences will quickly cause head gasket leaks.
You can get ARP head studs and increase the torque a bit too, but
that's probably overkill for a street car.
I presume you're doing the water in the oil thing instead of the
"blowing all of the water out of the radiator" deal (caused by
combustion gases in the water passages). Water in the oil can also
be caused by fig 8 gaskets. I've seen that caused by poor cleaning
of sealing surfaces, or by uneven surfaces on the sealing
surfaces. Combustion gases in the water is generally caused by no
liner protrusion, or differences in liner protrusion, or a cracked
head, or even a cracked liner.
I don't recommend an additional gasket - you've just doubled the
number of surfaces that can leak.
By the way, I coat the block / liners / head / head gasket (and fig 8
gasket) with Gaskacinch - seems to help things seal without being
overbearing. Be careful on the fig 8 deal - I got a little on the
surface between the liner "foot" (the protrusion below the fig 8
gasket) and the block and then couldn't assemble (and had a heck of a
time disassembling).
If you are totally sure that the fig 8 surfaces are good, the fig 8
gasket has no burrs, but you have a liner that sticks up a few thou
more than the others, it is possible to shorten it using a plate of
glass with a sheet of sandpaper / fine emery cloth taped to
it. Carefully run the top surface across it in a figure 8 pattern -
check length frequently as going to far ruins the liner. You have to
be VERY meticulous in this to not get the top of the liner slanted
too. Takes less time that you'd think. BE ABSOLUTELY SURE this is
necessary before doing. Usually there's a piece of grit on a figure
8 sealing surface instead of a liner that's too long.
One other thing - there's a slight chance that too much advance
causing ping would cause head gasket problems.
- Tony Drews
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