6 Cylinder stags

[Mike Wattam <MikeWattam@domain.elided>]

Hi Brian

The Stag running prototype had a 2.5 motor in it, this was mainly because a
Triumph 2000 was used to make it from.  Initially it was planned to use the
straight 6, but the gestation period was long and eventually it was decided
to use the V8 which was part of the OHC family of engines.  

This family as envisaged and put onto the drawing board, went from slant 4
of 1.5 litres, to V8 of 4 litres using fuel injection.  I remember seeing
something somwhere claiming that the V8 could go to 4.5 litres, but this
may have been hot air.

The V8 2.5 injection version was initially tried in other working
prototypes but this was both gutless and had unreliable FIE, so the
carburrettor 3 litre eventually became the motor used.

When the Stag was relatively new on the road, as a result of engine
problems a number of firms set up to swap out the Stag V8 for mainly Rover
V8 or Ford V6 motors, although Hurley Engineering in Coventry also put in a
number of Triumph Straight 6's.  Hurley liked to put Ford motors in
anything that moved, their speciality at the time being to remove Wankel
engines from NSU Ro80's and put in a 2 litre Ford V4.  Nice!

So, the Stag was never supplied ex-factory new with the straight 6 and your
NZ one must have been converted at some point.

One set of facts to note is that although the TR6 PI initially had a rather
peaky 150bhp motor, it was detuned to c130bhp in 1972 with a cam and piston
change, and the TR250 had carburrettors which removed even more bhp to
c110.  Similarly the 2.5 PI saloon started at 132bhp but when carbs were
substituted in 1975 to overcome FIE reliability problems, the power fell to
c106bhp.  I mention this to show you that there can be a wide variation in
power outputs of the straight 6 in the Stag.  They all have one thing in
common - not enough neddies!

Mike Wattam
Chairman - Triumph Stag Register