Abstract: A grain drying apparatus uses the heat of an engine to aid in the evaporative process. The grain drying apparatus provides an engine 20 which is used to power a fan 40. Waste heat generated by the engine is transferred to air driven by fan 40 through air duct 70 by three principle means. Air is initially warmed by contact with the engine and its radiator prior to entering the air duct 60. An exhaust pipe 50 and catalytic converter 52, carried by the engine, extends a part of the length of the elongated air duct 70, warming the air flow within the duct by contact. A finned heat exchanger tube 60, also carried within the elongated air duct, transfers heat to the air flow within the duct. An air intake pipe transfers air under pressure into a fuel tank, where the air mixes with fuel vapors. The air and fuel vapor mix is then transferred to the exhaust pipe, where combustion takes place, thereby increasing the heat flow from the finned heat exchanger.