Hi Greg.? I was interested in your comments below.? It sounds like the extreme
engine you built is very similar to the SCCA legal engines I was running in my
TR-4 the last few years I was racing.? I had to use a stock crank (by SCCA
rules), but otherwise pretty much the same.? We got 180 HP at the crank at
6,500 RPM's.? I used 7,000 when needed during a race, but we didn't want to
push it that far pn the dyno.?
Thanks for sharing your experience.
Jack
On Tuesday, September 5, 2017, 4:21:44 AM EDT, Greg Solow via Fot <fot at
autox.team.net> wrote:
In all of the research and reading I have ever done the idea has always been
to have the clearance between the head and the top of the piston at tdc as
small as possible with no actual contact.? This normally results in the top of
the piston under the "quench" or squish area being clean, with no carbon
deposits after running. In an engine with a race prepared stock crank and
modified stock TR-4 rods this distance is .026".? At this clearance using a rev
limit of 6800 RPM there will be no contact, at .025" the pistons will touch the
head.? This is also with Hepolite "Powermax 87mm" liners and pistons.? Forged
pistons probably expand more? with heat than these pistons, billet rods & a
billet crank probably stretch or flex less.? These days I usually shoot for
about .028" clearance when setting up the engine.? ??????? The most powerful
engine that we have built used HD LA Sleeve 87mm liners that are thicker then
the Hepolite liners, Forged pistons, std. size valves, & a billet crank. It
used Weber 45 DCOE carbs with 42mm chokes & carefully tuned 4 into 1 headers?
with a tuned length exhaust pipe with a megaphone on the end. This engine made
peak power at 7,000 - 7,200 RPM.? It had a 13.4:1 CR with a 306 degree duration
cam giving and actual .525" lift at the valve. The piston to head clearance was
set up to be .028" under the squish area.? This engine made 189 HP at the
flywheel with a very broad torque curve that peaked at 5,000 rpm, if I remember
correctly.? It was built to run on 110 Octane ERC Racing gasoline.? The total
advance at 6,000 RPM was 34 degrees. ?????? The compression ratio is clearly
related to the camshaft duration and both are related to the Octane rating of
the gasoline the engine is going to be run on.? I would certainly not try to
run this engine on 102 octane fuel. You would have to retard the timing way
back and the engine would just not run well. To run on 102 Octane fuel, I would
think that the compression ratio would have to be lowered to somewhere around
11:1 to avoid detonation & the engine would loose a lot of torque which could
be only regained by shortening the cam duration.? ????? Maybe the results the
Christian Max got have to do with the lower octane fuel that he has to use. We
do not have that issue here in the
US.?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????
Greg Solow?
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