This engine was intended to run at LeMans, but rule changes outlawed it before it was ever fired. Displacing 427 cubic inches, it was out of place in a class limited to 183 CID. Two engines were produced. One even made it into a test car. Even though mainly of aluminum construction, this monster weighed 577 lbs. But it was no boat anchor. The Calliope produced 630 (supposedly reliable) horsepower at 6400 RPM.

While displacing 427 cubic inches, the Calliope was no FE family engine. It used an aluminum block engine with cast iron cylinder liners. Bore was 4.34", stroke was 3.60". The unique feature of this engine are its twin camshafts, one for the intake valves and one for the exhaust. Both are in the block in an over-under arrangement. The intake camshaft lies 6" above the crankshaft centerline. Pushrods from the intake cam run parallel to the cylinder bores. The exhaust camshaft is found 4.5" above the intake cam. Its pushrods lie in a horizontal plane. The camshafts are driven by chains as are the pressure and scavenge pumps for the dry-sump oiling system.

The aluminum cylinder heads feature 3 valves per cylinder, two intakes and a single exhaust, in a pent-roof combustion chamber. The heads are sealed with copper O-rings. No intake manifold is used. Hilborn style injection stacks are cast integrally with the cylinder head. No coolant passes between the block and heads. External water lines are used instead. To shorten the engine to assist in fitting it to the racecar chassis, the standard front mounted water pump is replaced by two pumps on the cylinder banks, similar to the scheme used on the Flathead V-8.