A fuel-air mixture is supercharged by a stuffed crankcase of an engine and is forced into a large volume reservoir from which it is metered by a throttle to intake valves of the engine. The fuel-air mixture in a carburetor is adjusted automatically by vacuum and/or mechanical linkage in accordance with air flow through the carburetor. Oil is forced from a sump in the reservoir by the pressure of supercharged mixture in the reservoir, through small orifices in an oil line to lubricate the engine. A second engine has radically cammed intake valves in addition to conventionally cammed valves, and valving provided between a large volume reservoir and the radically cammed valves is closed at engine speeds below 4,500 r.p.m. and is opened at speeds above 4,500 r.p.m.