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Re: GT6 Tuning Advice Sought

To: "Barr, Scott" <>
Subject: Re: GT6 Tuning Advice Sought
From: Bob Lang <LANG@ISIS.MIT.EDU>
Date: Mon, 19 Oct 1998 09:47:05 -0400 (EDT)

I'll put in $.02 worth...

If you want to get that HP number up a bit, it's no secret that you have
to make the engine breath a little better. Given your budget of $2000 -
you should probably get a good tuned header and get is jet-hot (or other
brand ceramic coating) coated. This plus a free flow exhaust will make it
breath better out the back. You should then spend some time and port match
the intake and exhaust interfaces - this is legal in almost all forms of
motorsport - even for some interpretations of stock rules (although SCCA
does frown on this for stock Solo II classes...). Seeing that you are
going to coil overs in the front, I'll presume you are running in some
non-stock class. 

Now, you did not say if you were doing the work yourself... this has a 
big bearing on cost, as you can probably imagine. If you are, the above 
work plus the general balancing thing on the reciprocating parts will get 
you closer (and above) to the rated HP of your engine. One source 
indicates that going to Webers (probably out of the question given your 
budget) and a header, a free flow exahust and a good balancing job will 
make a TR6 engine go up to 120 to 125 HP, so it should be easy to get a 
GT6 motor over 100 HP.

As for intake - Webers are kool but pricey. And the initial cost is more 
or less the tip of the iceberg - so if you want to stay in budget, lean 
away from those. You could probably go to some equivalent SUs, HS4's, I 
think and get some more tunability. If you do go to header, you'll need 
to tweak the mixture curve on your carbs, so the SU's are better than the 
Z.S. carbs in this regard, although the Z.S. carbs can be tweaked. In 
either case, you should plan to run some sort of free flow intake filter 
like K&N or some of the other foam element types.. This helps a lot, in 
my experience.

The last thing to do would be to remove any parasitic loss on your 
engine. Being a GT6, that would equate to removing the stock fan and 
adding a thermostatically controlled electric fan. This is good for 
several HP, and I've read that number up to 8HP on a TR6 - the number 
would be similar on a GT6.

You have not taken your motor apart yet - or you did not mention that. It 
is possible that you'll get into that and find problems. If so - then 
you'll obviously need to deal with those before you start playing with 
induction/exhaust. If your car has lots of miles on it - a good 
"de-coking" will make it breath a lot better. If the bores are still 
round and not tapered and if the pistons are in good shape - this will 
save you money - if not, this stuff ads up fast.  Real fast.

There's lots more to be said, but this is a general primer. If you want 
some opinions, feel free to ask. I'm not a big expert or anything, but I 
have been able to free up some power on my TR6, so I at least have some 

Oh, and get the Comp. Prep. manual for TR6 and check out the web site:

There's lots of good general 2.5 liter in-line Triumph six swilinder stuff 
there including cam info. But the info is applicable to 2 liter Triumph 
motors also.

Bob Lang                Room N42-140Q          | This space for rent.
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