On Sat, 14 Dec 1996 10:30:30 -0600 Chad and Christy Stretz
<ccfarm@tranquility.net> writes:
>Hugh,
>>From my understanding the water ports don't match up. A friend of
>mine
>tried to do this some time ago, and that was the reason his swap
>didn't
>work. I could be dead wrong here, probably am, nevermind.
>Chad
Hello all from Oz.
As I understand it, all late (mkii) Triumph 6 cylinder heads are from the
same casting, however they are machined to suit the application. This means
that the swap will work in terms of fitting, but will produce an engine
with a different compression ratio to that desired.
Taking out the trusty manual, a GT6+ or GT6 mkIII for the US market will
have a CR of 8.5 or 7.5:1 (against 9.5:1 over here). This would probably be
similar for the US TR6 (?). Anyway, the difference in capacity is 25%
(2000cc v's 2500 for the TR6), so by bolting on a GT6 head then the
compression ratio of a 2.5ltr motor would be 9.4:1 (7.5:1 GT6 head) or
10.6:1 (8.5:1 GT6 head).
Although neither of these figures are exceptionally high, you will have to
do some serious tuning (especially ignition) to allow this to run properly
without 'pinging'. As I believe that the octane ratings in the US are lower
than here (we still have fully leaded fuel available at over 96 octane).
The other thing will be the valve sizes. I'm not sure if the TR6 has bigger
valves over there, but the PI version here certainly does. If the valve
sizes are smaller then the motor wil be a little strangled!
Best of luck.
Bill
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