Hi Roland,
According to my calculations even if the pistons were not concave their
protruding into the combustion chamber 0.030" would only decrease the
combustion chamber volume by about 1.8 c.c.
The original combustion chamber volume on the 100 is around 425 c.c. so
the slight increase in compression which would result from the decreased
volume of the bowl in the piston would be no problem.
As far as the strength of the piston is concerned there is usually
plenty of material in the head of a piston to remove 0.030" without
causing any problems. It would however be prudent to check the thickness
of the piston crown before actually zipping the top off.
The only other thing that I can think of that may be of concern is the
distance from the top of the piston to the first ring groove. It is
probably something like 0.300" so 0.030" sould not be a problem.
Michael Salter
www.precisionsportscar.com
-----Original Message-----
From: owner-healeys@autox.team.net [mailto:owner-healeys@autox.team.net]
On Behalf Of Roland Wilhelmy
Sent: Sunday, June 13, 2004 11:50 AM
To: healeys@autox.team.net
Subject: how much can you take off the top of a piston?
A friend of mine is building a 100 4-cylinder engine to M specs. He
has new pistons, offered for that purpose, concave top. Installed in
the block they project .030" above the block. There is no way of
knowing the past history of the block and how much it has been shaved.
Question: is it safe to take as much as .030" off the top of the
pistons? If not, is getting a thick gasket from someone like Mordy
Dunst a viable solution? If not, what then?
I will relay replies to my friend.
-Roland
BN1 my engine's already rebuilt
BJ7
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