The engine is a 2.8-liter V6, but we put in new pistons that raised the compression from 8.9 to 1 to 13 to 1.

The new pistons proved to give more speed and better fuel efficiency.

Boring out the cylinders would have required new pistons, of course.

And when things got noisy, along about 675,000 on the clock, there was an engine rebuild, with new pistons and such.

It got new pistons with four rings.

Further improvements in later years included new pistons, rods, crankshaft, and an in-pan oiling system.

Encouraged by this success, Manly started scaling up the engine with larger cylinders and new lightweight pistons.

The new pistons shed more heat, expanding less than their lower-tech cousins.

Engine compression was raised by new pistons.

The new reciprocating piston was located parallel to the barrel and below it, allowing the gun to be mounted lower to the ground.