pw520a 19 Report post Posted July 28, 2021 on my rebuilt stock 390 I have a petronix 1 with a flame thrower coil and I am gaping the plugs at 040 it runs fine, but not sure if gap is correct? Also I have been using the highest octane gas at the pump, once again its running fine but do I need the highest octane? Quote Share this post Link to post Share on other sites