The Holt 75 engine was a large four cylinder gasoline tractor engine used on the Holt "Caterpillar" tractor of 1915. This set of drawings describe how to build a model of the "75" engine of 1915 which details the complete engine, including a carburetor and ignition system, the engine is governed by a fly ball govenor as was the prototype and has a water pump driven off the cam and timing gears.
