In a message dated 7/3/03 11:20:28 PM Pacific Daylight Time,
owner-mgs-digest@autox.team.net writes:
> The unit is a 1589 bored + .060"; ported and polished mkII head that has
> been over-milled by a succession of unknown owners; 270 degree cam; stellite
> valves; and flat-top pistons. Performance is fairly respectable, but the
> high compression caused run-on, and presumably, blown head gaskets. This
> time I cc'd the head and found the CR to be about 13.5 to 1. A little
> excessive for the local 93 octane.
>
Whoa - you have one seriously planed head there.
Last 1622 I built (using the larger chamber head, of course) was a similar
compression but had BIG pop-ups on the pistons. The stock big bore flat-tops
for
the 1588 using the small chamber head that you presumably have gave about
10:1 as I recall.
What that means is that the rocker geometry in your head is shot to hell, and
it will wear out in a much shorter time than you'd want or expect. You could
consider shimming the rocker pedestals to restore geometry, but part of your
gasket blowing problem isn't just the high compression, it is likely to be a
thin deck on the head that warps under heat, and you are never going to
stabilise that no matter how many head gaskets you use.
If you started with another head, you'd restore geometry AND deck stiffness
and be where you want to be. If you really want to become a pro in head gasket
changes, I'd suggest that instead of sandwiching two gaskets, which may or may
not work for long, you invest in having a thicker gasket made from copper
sheet. It should last longer.
Bill
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