Abstract: To decrease spark advance upon high-speed operation of a separately ignited internal combustion engine, a spark advance centrifugal timing element, engaging a timing cam, is constructed to be formed of two link elements connected together by a knee joint having a limit position defined by a stop and biased to be normally in that limit position but, upon excessive deflection upon high-speed operation of the engine, permitting breaking of the knee joint counter the bias force so that one of the elements, namely the one engaging the spark advance cam, can deflect with respect to the other and effect some spark retardation with respect to the previously commanded spark advance.

Abstract: An annular permanent magnet affixed to the bottom of the timing shift plate of an ignition distributor exerts a force attracting the timing shift plate to the fixed carrier plate on which the timing shift plate is supported by spacers. Another permanent magnet is set into the inner flange of the carrier plate in the neighborhood of the cam-following portion of the interruptor to attract the nesting inner flange of the timing shift plate, so as to prevent the play between these flanges which form the bearing for the timing shift plate from interfering with the ignition timing. The timing shift plate and carrier plate are made of iron and there is only a small gap between the outer peripheries to provide a return magnetic circuit.