James---I just knew if I tried to shorten my sometimes lengthy replies,
the one on "compression ratios" would bring up the 'what ifs'. You are
right, of course, that it's not as simple to get a 9.5: 1 by taking off
a fixed amount. What's needed also is knowing the original head
thickness before milling begins. Since the one requesting the
information told me it was an unaltered head from a '73 then it is
indeed possible to use a formula to figure how much to cut. In this
case, .110.
One one is going for the highest possible compression ratio I would
agree that c.c.-ing the head volume and decking the block is necessary.
I don't beieve this is needed for the relatively mild 9.5 so I didn't
include these extra steps.
I DO like to be challenged on what I write, as the purpose of the list
it to assimilate information about the TR250/6. I hope the above cleans
things up a bit.
As it turns out, the head in question was later discovered to be one
from perhaps a '75 or '76 TR that has the lowest of compression ratios.
A revision on how much to cut is now in order.
The Comp. Prep. Manual for the TR6 is an excellant source for
performance improvements. My information on headwork comes from here, as
well as the AUTO MATH HANDBOOK from HPBooks.
Dick Taylor
Los Angeles
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