++> The main idea is to get some more power out of the old 2 litre lump.
++> aiming at something between 130 and 150 bhp and no I don't want to swap
++> for a 2.5 litre unit. So, can anyone tell me whether my assumptions are
++> correct and if so, should I gor for the SUs or the Webers. Should I go
++> for a double or for a triple carb setup?
++>
++> Sigh. You can't just swap the carbs and expect to bump the horsepower 30 to
++> 50%. You're going to have to do some homework and make some decisions. Star
++> off by purchasing the TriumphTune catalog and reading it and making sense o
Double sigh. I have been meaning to get on my soapbox about increasing
engine output for some time. Now those of you that know me, realize that I'm
all in favor of increasing the performance and reliability of our cars. After
all, I
stuffed a GT6 driveline in my Spitfire and I think it is great. But I have
to say that increasing the power of your engine isn't the only way to increase
performance of your car AND it isn't always the best either.
The first thing is that the GT6 MK II or MK III engine is a far better
choice of engine to start with. The Triumphtune catalog discusses a few of
the reasons. But i'll tell you the best reason is that you CAN use a TR6
crankshaft and up the displacement to 2.5 liters. 150 Hp out of 2.0 liters
gives 1.23 hp/in^3 which would be a very unreliable powerplant. 2.5 liters
on the other hand, changes that figure to 0.98 which is much more
reasonable. In fact many production engines hit that mark these days.
But back to my original point. There are many areas where
you can really increase the performance of your car without significantly
changing your powerplant. You'd think that at 150 hp your GT6 would
be a match for most modern sports cars. Unfortunately, you'd probably
be often disappointed. The GT6 (most all cars from that era) suffer with
a tremendous amount of rotational inertia in the drivetrain. I haven't done
the math, but I'd bet a pair of nice light alloy wheels and a lightened
clutch/flywheel assembly would give you a more reliable performance
increase than a carb and cam swap.
I'm not trying to discourage you. On the contrary, I encourage you
to jump right in and modify your car. Just take the advice of the people on
the
list and work on the car as a system. As you finish your restoration, look for
ways to reduce the weight of your car, especially in rotating parts. Stay
realistic
in your engine performance goals - i.e. stay at or below 0.95 hp per cubic inch
displacement. Think about increasing the braking ability of your car. Good
luck...
--
William Woodruff woodruff@caen.engin.umich.edu
Ann Arbor MI
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