the "kickback" is the reason why MCFA added a 1/2 second spark delay to the 4.3 GM equipped models, as the delay, (if correctly installed) allows the starter to engage before any spark is introduced. This is more a function of how much compression these engines hold than anything else, and the result of the kickback is usually a broken nose cone on the starter, or a broken block where the outside starter bolt mounts to. In CARB (emmission controlled by computer) trucks, the crankshaft sensor sees 1 complete revolution before allowing spark.