Abstract: An internal combustion engine has the usual gasoline tank, electric starter, cam-operated fuel pump and inlet and exhaust manifolds. The exhaust manifold is converted to a heat exchanger by running steel tubing therethrough having an inlet connected to a second electrically operated pump and an outlet connected through electrically operated normally closed shutoff valve means to the intake conduit of a standard L.P. gas carburetor. The carburetor is connected to the inlet manifold by a base plate connected through an electrically operated shutoff valve to the cam-operated pump and provided with spray jet means for supplying liquid gasoline spray to the inlet manifold for starting.