Look at the porcelin for 2 things: The optimum A/F will result in a 'light gray' dusting, and if the procelin shows ANY tiny black flecks this is an indicator of detonation. If there are any black flecks present back off the timing, clean a test plug and then recheck it after running another 1000 miles.
If the plugs show any 'reddish' color they're too hot (without using octane additive as this will turn them reddish normally)
A forum community dedicated to Ford Mustang owners and enthusiasts. Come join the discussion about performance, builds, modifications, reviews, engine swaps, classifieds, troubleshooting, maintenance, and more!