Just wondering what people’s feelings are on spark plugs. I’ve used the stock plugs specified by the manufacturer (AC MR43T) standard tip, and Accel 586 projected tip. I was hard pressed to see a difference if any. Any advantage to using projected tip over standard? I’ve read some info on the Jacobs ignition site, but I want to see what you guys prefer. I’ve got a 383 sbc with late style heads (Not Vortec), with dished forged pistons 9.5 cr. I’ll be upgrading to a high grade electronic ignition system this year.

Paul

the projected tip is more out in the chamber, so it will warm up faster and should give a little better flame travel, and hoursepower gains, well maybe a bit on a high output engine but on a stock motor you will not see much at all,

Extended (or projected) tip in the proper heat range always worked better for me in a hi-perf marine application with big blocks. Can't say for sure in your case, but I WOULD give the extended tip a try. --- Jer

I was using the projected tip Accel, and it seemed to work well. I've got a 383 stroker with a mild cam, ported heads, and forged pistons.

any suggestions on what spark plug to use and the gap for a 02 500 hp efi with msd system?

I've seen longer life and better idle with extended tip plugs. Both in the boat and in the Hi Po car engines.
Hard to tell if more HP but they do run better, seat of the pants..

Dennis Moore discusses this subject in detail on pg. 177 of his"BBC Marine Perf." book. (I knew I had it somewhere) Bottom line.....projected tip is what you want to use. --- Jer