Rapid Fire spark plugs questions.
 

Stock '99 502 MPI motors.

Gonna pull both motors on Sun to replace the drive couplers. Figure thats the time to replace the plugs. :rolleyes:

Anyways, did a search on the AC rapid fire #1 plugs, Seems everyone has had great results as far as cleaner transom and better idle. Correct????

What should I gap them at..... .035, or .040?

Will changing to these plugs effect any other settings? Timing, fuel mixture?

Thanks

.040

Ob, Why .040? My 2000 says .035. I have used this for 2 years now with no problems with the Rapidfire #1's.

Would not .040 require more voltage out of the coil to properly spark? Or is the merc coil able to provide the larger spark?

Jerry,

I used the #1's and they cleaned up my transom a great deal when I was over-carbed on my old Holly. If you gap them at 40 there would be a theoretical performance gain. The #1 requires a little less voltage/current to produce the same energy under the same circumstances. Under higher cylinder pressure excess gap is bad. Spark may break down. With stock compression you should be fine. With the older Merc ignition setup a large gap places more "stress" on the ignition module and can lead to premature failure. A friend of mine used to maintain a fleet of tow boats in Florida and some NASCAR fan gapped them all at 45 prior to his arrival and many ignition modules failed. Merc denied the warranty claim.

FREE
4 new but old style Rapid Fire #1's These have fluted upper ceramic part. ACDelco techs said best not to mix with new style smooth style plugs.

I am trying the Bosch plugs now.

Fountainclimber

I used Rapid Fire #1's in my 502mag mpi with great results. Much improved idle and better performance all around.

YEP,, WHAT BAD DOG SAID !!!! Dont expect to see any real gains,,, I run the because they get to running temp faster, so they dont foul up at start up, and have a more complete burn where the less transom soot comes into play. Also,,, they are alot more pricey,,, but when I went tp change them after 1 season they looked great. I changed them because I had the new ones right there, but I would think you could get 2 seasons out of them.

RIGHT !!!!!!
 

RIGHT !!!:D LMAO

LOL :D

guys what is the part number of the rapid fire #1's your using on the1999 502 efi's?