Typically for a street engine that hasn't had a lot of modifications and no amplifier box (like a HEI system with an aftermarket coil) the "base" spark plug gap will be 0.040 to 0.045. For any aftermarket, performance ignition system, we start the "base" spark plug gap off of the engine's compression ratio and then fine tune it from there, opening the gap by 0.005 to obtain the best performance. The more compression, the less gap:
up to 10.5:1 -- 0.050 to 0.060 10.5:1 to 13.0:1 -- 0.040 to 0.050 13.0:1 and up -- 0.035 to 0.045 A larger gap will provide a smoother idle and more powerful spark but can cause misfire at higher RPM. In your case, with either the MSD 6 or Digital 6+. You should be able to start around 0.050 and experiment up to 0.060. Note: For best performance you will want to have a quality set of helical-core ignition wires. Kind regards, Don Hoeschen Granite City Performance custom engineered competition components http://www.granitecityperformance.com/ ---- [email protected] wrote: is it adviseable to widen your spark plug gap when using a MSD ignition box, a digital 6 plus or a 6? (2- diffrent cars)-- if so what should it be? for a 350 slightly built. thanks! Harlan
