[1] The horizontally opposed, four-cylinder engines in this family are all identical in appearance, bore, stroke, dry weight, and piston displacement.

All feature a bottom-mounted updraft carburetor fuel delivery system.

The higher power variants differ only in compression ratio and maximum allowable rpm, plus minor modifications.

[1] In all models of this family of engines the cylinder heads are of aluminum alloy, screwed and shrunk onto steel barrels.

The engines all employ hydraulic tappets which operate in aluminum guides that are machined into the crankcase.