On Mon, 1 Nov 2004 AMC74Hornet@xxxxxxxxx wrote: > What would happen if you had a coil with a built in resister > and added an external one? To weak a spark to start the engine > or just poor engine peformance period? Yup, you're right, all of the above, due to weak spark. Basically, spark coils soak up electrical energy, storing it as a magnetic field, to be used when the points open (when spark occurs). You make more magnetic flux by passing more current in the coil primary, essentially. You can use higher-current coils but your points will wear out faster. There's other limiting factors, but a lot of basic "high performance" coils are mainly higher current primary windings (plus better construction, insulation etc on quality products like Accell).