Stock 440 motor home pistons or passenger car pistons?
If passenger pistons which year and do you know if they are flat tops, flat tops with valve reliefs or what motor they were made to fit in? work scope
the reason I'm asking these questions is to try and see if you can post or know closely what the compression ratio the motor has now? help
That NJK #4 spark plug is a real hot spark plug, don't run it tsk
If that type plug is a tapered seat plug with a extended tip see if you can a #6 or#7 plug number like that one scope.
If it is retracted gap, center part flush with the main plug body, then see if you can get a tapered seat plug with a extended tip in #6 or #7 heat range and try them scope twocents

Last edited by Cab_Burge; 04/15/21 09:58 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)