Crank Trigger Wheel Flying Magnet Sbc 7 In. Black Replacement Wheel For Small Block Chevy Crank Trigger Kit (P/N 86103) MSD IgnitionMost crank triggers have a wheel, with steel studs sticking out, bolted to the harmonic balancer. As the crankshaft turns, the studs pass by a stationary magnetic pick up, triggering the ignition. This pick up can be triggered by other bolts, debris or even vibrations which will cause a loss of power or engine damage. The MSD Flying Magnet Crank Trigger uses four magnets secured in the aluminum trigger wheel that pass by a stationary non magnetic pick