Whilst originally seen as little more than a convertible version of the Triumph 2000 saloon, as development progressed the Stag gained its own identity until the final design shared no body panels or pressings with the 2000.

The V8's Bosch fuel injection was running into numerous difficulties in development and King was unable to convince Leyland to divert extra funds to Triumph to solve the problems.

To maintain the required power output the capacity was increased to 3-litres, which then entailed modification to the Stag's other drivetrain systems including the gearbox, back axle and brakes.

This relatively 'last-minute' capacity increase was achieved by expanding the bore of the engine instead of the stroke, which explains the Triumph V8's unusual 'oversquare' internal dimensions.

As well as its unusual construction (the crankcase and cylinder block were made from chromium iron whilst the cylinder heads were aluminium alloy), the engine featured a unique arrangement of studs and bolts attaching the cylinderheads that allowed the cylinderheads to be removed (in design, not in reality) without firstly removing the overhead camshafts and disturbing the valveplay adjustment.