4) What modifications do I need to make a TR6 motor fit? Also, I've heard
that there isn't much of a performance gain because, although the TR6 motor
has an extra 500 cc, it doesn't rev as nicely because of its longer stroke.
----------
Karim-
Well, it sounds like OPINION time here at the ole keyboard...
It is true that the TR6 motor does indeed have almost a 3/4" longer stroke,
(about the same as a TR4 motor) but neither the GT or TR motor can exactly
be construed as a "short" stroke motor. The stroke length has something to
do with some sort of convoluted British tax law that rewards the engine (of
similar size), with the longest stroke. Something to do with the stroke
length, divided by the bore size, multiplied by the steering wheel
diameter...or something like that, I'm sure our "rightside" pond dwellers
can elucidate...
Everything is kinda relative. Some people feel that an MGB is a "high"
revving motor. The stroke is actually between the GT and TR motors. Few
people feel that a Jag V12 is a hi revving motor, but the stroke is about
an inch less than a TR motor. (When's the last time you heard an XJS at
7000 RPM ?)
My feeling here is that torque is a bigger player here than RPM. That extra
500cc's shows up in the "seat of the pants", at useable RPM ranges, more
than on a dyno. (Crank pin angle, rod length, angular thrust...all that
weird SAE talk, makes the difference.)
What I'm tryin to say here is that I feel that you will see a bigger
difference with the TR motor than you would expect on a street car (I think
in full and equal racing trim it would be tough to show a "lot" of
difference between the two).
OK, now what do you need to put it in a GT chassis. Unless you have a
set-o-webers for the GT engine (they use different manifolds), you must use
the GT intake manifold. This manifold only bolts up to the GT head (no, you
can't put the GT head on a TR block easily), or a TR head from 72 and on.
So you need a late motor, or at least head, and the GT oil pan. (The TR pan
is just a little too deep at the front.) After that, most everything is
easy to deal with.
Remember...if you don't exercise that opinion of yours...someone else will
!
Nick in Nor Cal
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