Hi Barry
AFAIK the standard GT6 cam can be replaced with one from an early 2.5 PI
saloon (Stanpart no. 308778). I'm not sure if this cam will fit GT6 Mk1
engines or by how much it will increase power.
I've also heard that a 2500 saloon crank and pistons can be fitted. Anyone
any ideas or comments?
>From what I've read and heard there are various other (sometimes
contradicting one another) opinions, theories and ideas on getting more
power from a GT6, but herewith some interesting alternatives:
1) Fit a 6-3-1 exhaust. It will apparently boost power throughout the rev
range. ( Apparently one of the best improvements to make). Or keep the
standard cast iron exhaust as it apparently provides decent mid -range power
and torque. 6-2-1 exhausts apparently don't work very well in the mid-range.
The True/false ? Some articles differ and advise to use 6-2-1 exhausts.
Anyone any ideas or comments ?
2) Replace standard cylinder head with one from a post May 1975 2000/2500
saloon (Stanpart no. 219016). I'm not sure if this head will fit GT6 Mk1
engines. Anyone any ideas or comments ?
3) Keep the twin Stromberg 150 CD carburettors and fit K&N free-flow air
filters (apparently torque will be lost with anything bigger and SU HS6
carbs are apparently only good a 2500 six cylinder engine). Some articles
differ and advise to use SU HS6 carbs. Anyone any ideas or comments ?
4) Replace carbs and fit fuel injection from a 2.5 PI saloon (recalibrated
to work on a 2000/GT6 1998 CC engine). Apparently a 2000 PI / GT6 PI
produces approx the same BHP as a 2.5 PI, but slightly less torque. However
a 2000 PI / GT6 PI will rev past 6000 whereas a 2.5 PI tends to destroy
itself. I'm not certain exactly which parts are needed for such a conversion
or if it will only work with GT6 Mk2/Mk3 engines. Anyone any ideas or
comments ?
5)Replace the entire engine with one from a 2500 saloon / TR6 (carb) or
better still replace it with one from a 2.5 PI saloon ( TR6 PI).
A few other ideas to consider:
1) Use a TR4 - TR6 or 2000/2500/2.5 PI saloon gearbox instead of the
Vitesse/GT6 gearbox.
I have been advised that the Vitesse/GT6 gearboxes are weak, prone to
failure and troublesome. It WILL apparently fail if you put more than
standard torque through it or drive in a 'spirited' fashion. It will not
last with any performance increases. True/false ? Anyone any ideas or
comments ?
2) Use a 2L Vitesse/GT6 3.89:1 (if o/d fitted) / 3.27:1 (if no o/d fitted)
or custom (3.63:1) differential instead of the Herald/Spitfire 4.11:1
differential.
I have been advised that the Herald/Spitfire 4.11:1 differential provides
the wrong gearing, that it is also too weak and will fail if used with a 2L
GT6 engine.
3.89:1 is a good diff ratio, but apparently 3.63:1 is "the best" diff ratio
to use with the 2L GT6 engine and saloon o/d gearbox (possibly even with the
standard Vitesse/GT6 o/d gearbox). Unfortunately I have no idea where one
could obtain such a 3.63:1 differential, but the guts from a TR7 four speed
diff is 3.63:1 and could possibly be transplanted into a Vitesse/GT6 diff
casing. Anyone any ideas or comments ?
3) Fit a camber compensator to keep the rear suspension stable.
Joe Curry [spitlist@COX.NET] or [spitlist@gte.net] is making and selling
such a device. Not too expensive if you live in the USA and a worthwhile
investment from what I've read. Unfortunately there's a big pond between SA
and the USA, which has forced me to look at making my own camber compensator
device using the bottom leave from an old Herald leave spring.
4) Fit an oil cooler. Apparently a necessity to protect a GT6 engine.
HTH
Chris de Wet .
PO Box 472 , Ifafi , 0260 , South Africa .
My Spitfire6 project:
Spitfire(Mk2) body, GT6(Mk1) bonnet & doors, GT6(Mk1)
chassis/brakes/suspension, GT 6 (Mk 1) engine, 2000 Saloon gearbox with
overdrive and Vitesse 3.89 differential.
-----Original Message-----
From: bschwart@postoffice.pacbell.net
[mailto:bschwart@postoffice.pacbell.net]
Sent: Friday, 24 October, 2003 06:00
To: triumphs@autox.team.net; spitfires@autox.team.net
Subject: GT6 power increases -
I was just thinking with the discussion of TR6 (250) power increases (the
usual 150 hp) which basically gets a big increase from the fuel inject cam
grind but since the GT6 uses the same cam could one realistically expect
130 hp if one were to install it in a GT6? Of course the usual other TR6
mods apply here as well-
Sounds intriguing
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