Overtorquing distorts the cylinder and decreases power. Seen it on the dyno
with little bike engines. Best place to learn some of these things is trying
to squeeze the last pony (very small pony) out of a 50cc GP bike. When
you've only got 16 HP to begin with, everything matters. Even when the
driver is a 85 pound girl.
-----Original Message-----
From: owner-fot@autox.team.net [mailto:owner-fot@autox.team.net] On Behalf
Of mordy dunst/ gasket works
Sent: Tuesday, March 02, 2004 7:50 AM
To: FOT@autox.team.net
Subject: Re: re-torqing cylinder heads hot???
I aggree with Ted.
Composition gaskets creep ( de-gas) as the temp builds and the head clamping
pressure pushes any moisture or gas out. So, a new uninstalled fiber HG may
be .050 fresh but, somewhat thinner installed. If you follow this logic
then you ought to retorque warm to get rid of as much moisture/gas out then
re-check when cold to see if any slack has developed. How many times you
will need to follow this sequence is dependant on the accurate
reproducibility of torque specs on your wrench and how anal you may be.
Statistics would say that within three attempts at this will bring you to
99+% final.
Solid material will not to creep. So, the gasket thickness will be the
final installed height and the fasteners (if good) once torqued should stay
that way.
One other thing.... dynamometer testing has shown that "over-torquing" can
diminish HP rating. It does so I figure because the top of the cylinder
bore will bow ought (oh-so) slightly and perhaps not allow the top
compression rings to seal as well? I be not engineer... but, data is the
final arbiter. Comments from those with more knowledge?
Mordy
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