MODIFICATIONS TO FIT THE 2.5-LITRE ENGINE

1 Front plate 1

The 2.5-litre engine needs a few alterations to fit in the small chassis engine bay. Triumph saloon engines mount via their front plates, not via bosses on the side of the block. Cut the mounting lugs off the saloon front plate or fit a Gt6/vitesse item.

2 Transfer brackets

Handily – and curiously – the holes for the mounting bosses are still present and tapped on big saloon engine blocks. Run a ⅜in tap or – ideally – a thread chaser into each hole to clear the threads, then bolt on Gt6/vitesse mounting bosses.

3 Big end clearance

The longer stroke of the 2.5-litre engine means there’s not enough space for its big ends to clear a 2.0-litre sump. The big saloon sump fouls the small chassis crossmember and steering rack. The 2.0-litre sump therefore needs adjustment…

4 Modify sump

Place the 2.0-litre sump on the engine and turn the crankshaft to mark where the big ends hit it. Support the sump with a tube protecting its steering rack channel. Hammer neat grooves into the sump to create clearance for the front three big ends.

5 Swap rear plate

The big saloon engine is tilted at an angle of 8°, but it needs to be vertical in small chassis cars.

Fit a Gt6/vitesse rear engine plate to get the correct angle and alignment to the bellhousing. Ensure that the three 5/16in UNF studs are present at the top.

6 Use a 2.0-litre flywheel

The big saloon flywheel is too deep, unless it’s fitted with its own gearbox. Fit a Gt6/vitesse flywheel – which comes with the bonus advantage of being lighter. Fit a Gt6/vitesse spigot bush, too. Ideally, get the flywheel balanced with the crank.

7 Choose the right clutch

If you’re using a Gt6/vitesse 2.0-litre overdrive gearbox, you’ll need a Gt6/vitesse 8 ½in diaphragm clutch with a 1in diameter ten-spline driven plate to fit its input shaft. The big saloon gearbox has a 1 ¼in diameter ten-spline input shaft.

8 Change alternator bracket

Big saloon engines carry their alternators too high to fit under a GT6 bonnet. Fit a GT6 bracket to the block for the lower mounting. Use a Gt6/vitesse adjustment strap, which runs from the water pump housing to the top of the alternator.

9 Cooling system

Due to limited bonnet clearance in a GT6, you’ll need to fit a GT6 thermostat housing. A GT6 or Vitesse radiator will be adequate for the larger engine, as long as it’s in good order. It’ll work best if the original crankshaft-driven fan is retained.