Abstract: An engine block heater comprising a propane circulation heater in which engine coolant is heated in a jacket surrounding an inner chamber which is open at both ends to accommodate an industrial size portable propane torch. The jacket is inclined to the horizontal and has a coolant inlet and a coolant outlet which, in use, are connected to the engine block. When the torch is lit, coolant from the engine flows, driven by natural convection forces so that cold coolant from the engine is replaced with heated coolant.