The crankcase was a barrel-shaped aluminium alloy casting, with an internal integral diaphragm which held the front crankshaft bearing.

Forward of the diaphragm there was an integrally cast cam-gear case for the double track cam-rings.

Flange-mounted steel barrels were bolted to the crankcase and enclosed with cast aluminium alloy, screwed-on, cylinder heads with integral cooling fins.

The Antarès had a single pair of overhead inlet and exhaust valves per cylinder.

The cam-rings drove roller tappets, mounted in the cam-case, which in turn operated rocker arms, fitted with ball bearings, via pushrods.