Legal??? I've experienced many many inspections with the TR series of
engines. During those times we were not allowed to use anything but the
stock rods, cranks cyl heads etc. Modifying those parts gave good power and
more than fair reliability. Number one for power is COMPRESSION. Compression
works from rev one 'till you lose your nerve.The bigger the camshaft the
better the exhaust needs to be. the bigger the camshaft the higher the
compression needs to be. With my G-3 don't even think about anything less
than 10.5 and 11.5 is best. All that by milling the head not pistons. 87mm
bore is normal and was used in my last year of driving the TR-3 in 1960.
Good valve grind always necessary, this means thinned out seat area to the
edge of the valve and the pocket in the head eliminated inside that seating
area. All regular hop-up stuff applies. Considering the above statements and
maybe just following the ideas in the Competition Prep manual you should be
seeing a minimum of 140bhp at the flywheel ( not the rear wheels). Working
hard at it I averaged 155 without too much trouble with the S.U.'s . The
peak power was at 6000 and the top rev used was 6500 I used a configuration
much like this (less C/R and camshaft, cause not legal then) for a long time
and at a time when it was my only car not just a race car. This was a 135
bhp at the flywheel,It was quite normal to change the camshaft and the
cylinder head after driving home after the race so that I could go to work
with the same car the next day. Sounds like a lot of work....it was. But
whatchagointo do if you want to race?
Wheel dynos are great for tuning but not for comparison to other engines,
dynos, or even other days running. There is not enough accuracy involved.
You MUST have a correction factor for the day involved. That means:
barometer, vapor pressure,and accurate temperature at the carburetor inlet.
Without these you are just comparing the last run with the one just made but
not a reference to anything done that morning or even later in the day. As
the engine becomes more heat sinked the power will
change.....so...consecutive runs may be actually better in power but give a
lower or the same reading. On an engine dyno the temperatures are controlled
and thus you can do a lot more work, and consecutive runs, with excellent
accuracy. Clutch and rear wheel slippage,gear frictional loss all count to
reduce the accuracy along with the temperature of the oil in all those
little moving and rotating items. Wheel dynos are a good tool, I used one
a lot in the far past, but as a scientific instrument there is just too much
lacking in information & accuracy.. Kas Kastner
----- Original Message -----
From: <GRMTim@aol.com>
To: <fot@autox.team.net>
Sent: Wednesday, August 08, 2001 3:44 PM
Subject: How much horsepower?
> Okay, JK and I spent the day at the dyno with the Grassroots Motorsports
TR3.
> Remember, this is a near stock engine with the head shaved, a Kastner G3
cam
> a decent valve job and reworked SUs and a header and straight pipe.
> We started the day with 97hp ((4900 rpm) at the rear wheels and ended up
with
> 104.5. Torque figures started at around 115 ft-lb. at 4000 rpm and ended
at
> 120.
> JK says we are down nearly 30 hp to the front runners like Mike Jackson
and
> Jeff Snook.
> Okay, guys, give it up... what should a well tuned LEGAL TR3/TR4 engine
make
> for power, and what type of $$$$$ commitment will it take to get there?
>
> Tim Suddard/Grassroots Motorsports
> P.S, We are constantly updating our website and making reports in our
> magazine about this ongoing project car. www.GrassrootsMotorsports.com
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