The 643cc Steyr two-cylinder engine is accessed via a rear or top door and is reminiscent of a VW boxer engine. It has a split aluminum crankcase like the VW and carries a Nitrided forged crankshaft. The aluminum cylinder heads have hemispherical combustion chambers, with chrome alloy valves, hardened-steel insert seats, and cast-iron guides. The Haf’s engine sports a two-barrel Weber carburetor and compression ratios varied from a low of about 6.7:1 to as high as 8:1. Power output peaked at 30 SAE hp at a rip-snorting 4,800 rpm.