Anybody ever seen a 4 cylinder engine turned into an air compressor on two cylinders? Lots of Model A's were converted that way, using the whole front end- - - -front axle, gas tank, radiator, hood, etc. with a trailer hitch attached instead of a front bumper. A special intake and exhaust manifold ran the engine on cylinders 1 and 4, and 2 & 3 compressed the air with the exhaust valve disabled and a one-way check valve where the spark plug used to be. The 2 & 3 intake valves had very weak springs that let every down stroke draw air into the cylinder, and every upstroke compressed. Lots of jack hammers got powered by those rigs- - - -relatively low pressure, but lots of volume.
Jerry