head gaskets N notes about such

[Bruce Plecan]

Checking for straightness is mandatory, period.

When a headgasket general blows from detonation, it's generally from the
head being lifted off of the block surface more then the gasket can
tolerate.  This lifting can generate bending forces, but that is generally
in very HP applications (like 2+ HP / CI).   What kills things for getting
warpped is when you exceed the thermal limits of the material.   Headgaskets
that have blown from detonation, and then been overheated from the loose of
water is what really Fubars an engine.   When you overheat an engine, it's
REALLY easy to over the oil at the same time (syn.s included).  Also,
remember all the guages in the world are reading averages.   BTW, that is a
real down side with AL heads, the heat treat is at a rather low temp, and an
overheat to 300d (localized, sustained) can effectively turn the head into
skettie, it will never be right again, though it may seal just fine, for a
while, but given an excuse, my catostrophicly (?) over nothing (ie drop
seats guides from a hard run or mild overheat)
   Little addition items like watching you oil pressure in a cruise mod
while making chips.  If you do a chip and loose 10 PSI of oil pressure, your
putting tooooo much heat in the motor, and while the coolant maybe reading
normal the oil temp.  "at the" bearing my be nuts.  There is sooo much
windage in a pan again, any guage is reading an average, and may be
misleading.  That's why folks put engines apart as a matter of just normal
maintance.  To really really know what is going on.  On some of the really
fun stuff I've done engine tear downs were a 25K routine tear down.
   A Bluepoint (Snap-On) or major automotive tool supplier, can provide a
good straight edge.  Using a cheap straight edge is like poking a hole in a
condom, before use.
Bruce

> I would have the surfaces not only checked for straightness, but
> refinished, maybe even the block as well,  The surface should have a max
> .005" distortion to it, and a proper finish (120 rms?)  for good head
> gasket sealing.  Putting it back together and just cleaning surfaces
really
> isn't that god of an idea
> Just my.02
> John L. Calabrese

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