Abstract: A manifold heat exchanger for an internal combustion engine is disclosed as including an enclosed liquid receptacle having a heat receiving portion projecting into an exhaust manifold and a heat dissipating portion projecting into an associated intake manifold. The receptacle is partially filled by a quantity of liquid that is vaporized by heat from the exhaust gases flowing over the heat receiving portion of the receptacle. The vaporized liquid transfers heat to the heat dissipating portion of the receptacle so as to heat a combustible charge flowing within the intake manifold. The intake manifold is preferably located above the exhaust manifold so that gravity normally positions the unvaporized liquid within the heat receiving portion of the receptacle. The liquid receptacle also preferably has a mushroom shape with an elongated lower portion defining its heat receiving portion and a partially spherical upper portion that defines the heat dissipating portion.