An increase in CR will indeed increase horsepower but nowhere near 40-50%.
There are two or three formulae used to estimate horsepower, and some
software that does it pretty accurately. Using those sources, the figures
come out more like 3% per each point -- that is, 3% for the increase from
10:1 to 11:1, etc. I am surprised that the figure is so low, and I hope that
someone who has tested this out on a dyno will respond. This answer kind of
corresponds to what we have experienced when we have had to make a head
gasket change in an emergency situation. Changing from a shim gasket to a
stock gasket makes about one point difference in CR, but we were surprised
that this made no discernable difference in our lap times (which, of course,
may be due to driver incompetence).
Bob Kramer wrote:
> FOT,
> I know that some of the more seasoned and/or engineering types out there
> know the answer to this question. My machinist claims that an increase in
> compression from 10.5 to 1 to 12.5 to 1 will produce serious HP gains,
> something like 40 to 50%. Is that true?
>
> Bob Kramer
> TR3A, TR6, TR4A, Devin TR3
> Hill Country Triumph Club
> Corinthians Vintage Auto Racing
> rgk@flash.net
--
uncle jack
TR4 - 10 mpg
TR6 - 30 mpg
(they're right -- my mileage may vary)
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