Thread: 502 Ram jet question

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What is the correct plug gap for the 502 ram jet, I know it is pre 2003 but don't really know if it is the mefi3 or 4. One place shows .035 and another shows .045. I had already went with the .035 when I saw the .045. If it is .045 what will happen if I leave them at .035. It seems to be runing fine and a miss it had at idle is now gone. What I pulled out is about .045 but I figured they were worn. I used the spec AC Delco 4 rapid fire.

25164642 (Rapid Fire #4) Gap @ .045 is the plug for a RJ502

The wider gap is used because of the increased energy of the spark....
it takes a certain amount of energy to jump the gap at a specific
air pressure and humidity....if you have a high-energy spark system and have a narrow gap, the high energy is never reached since the gap dictates the voltage level required for the spark to jump.....therefore, for your system, the 0.045 inch gap is better if you want a hotter (higher voltage) spark. It doesnt matter if it is a MEFI3 or MEFI4, those are the controllers, not the coil (energy)system.

This is why changing the gap changes your timing.....tighter gap allows the spark to jump at a lower voltage level.

mike in tucson