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Buick 215/Rover 3.5L comments

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Buick 215/Rover 3.5L comments
« on: April 29, 1993, 11:46:43 AM »

First, thanks to everyone ...  Perhaps, I should have mentioned that I
have the Hotrod article, the Hardcastle Rover Book and info from various
tuners in the UK.  I've also chatted with Phil Baker on the phone a couple
of times.

If you look carefully at the the Hotrod piston/crank chart, you'll
notice that there is no piston listed that is approximately 94mm and
will give you a decent compression ratio with the stock crank.  The
Ford 255 pistons have a compression height of around 1.5 in while the
stock Rover pistons are at approx 1.8 in.  By the way, the reason I'm
picking 94mm is because I have read that that is the maximum size one
can safely sleeve to without breaking into the water jackets.  It is
also the size of the new Range Rover 3.9L pistons.  The 94mm Toyota
pistons look like a perfect match.

I do not want to change to the Buick 300 crank because the rear of the
block has to be modified and the crank hangs far enough out the back to
be a problem.  I'm also not interested in drastically changing the
intake, exhaust, heads, etc. at this point.  There is a Rover stroker
crank available in the uk but it is around 600 pounds.

I have a couple more questions.  What is the margin of slop that a
Felpro head gasket can handle?  Would a change from 88.9 mm to 94 mm
require more than trimming?  What is a good compression ration to aim
for given the engine and heads are aluminum and I'm planning on using
94 pump octane gas?  Currently the car is 10.5:1 and last time it was
running seemed fine with 94 and a little bit of timing retard. I was
thinking of around 9.5:1 to 10:1.  Finally, does switching to a
composition gasket like a Felpro from the stock steel shim gasket
really have a significant effect on compression ratio?  According to my
calculations that switch alone would lower the compression ration to
9.7:1 from 10.5:1.

Again, thanks for any comments ...

Rod Barman, Dept. of E.E., University of British Columbia