Hello,

I was wondering what spark plugs other people are using in their modified 455's. I have a modified 455 (stock heads ported with larger valves, tons of other stuff I won't list here) that I've been using Bosch Platinum Plus plugs in, and have had real good luck. My engine started misfiring today for the first time ever, and I found a plug with cracked porcelain (my fault?..who knows). I just wanted to see what other people are using before I replace these with the same.

I've heard some people say that platinum plugs are not to be used in performance engines, others say they should, others say NGK, others say AC Delco. I want to hear your recommendations and why.

Thanks.

 

I like a/c delco, ngk, and motorcraft.

 

I use Delco's most of the time. I have tried NKG's from olds performance products (just a colder plug) when I built the 455 In my old 69' cutlass, they were fine. IMO the high priced fancy spark plugs don't really make a big difference for what you pay.

 

The Bosch Platinum Plus are only $2.25 each from Napa in my hometown, and that's without my normal discount. I just want the best performance plug I can get, whether it be your normal plug, copper, or platinum.

 

Plugs I like: Champion, AC, Motocraft, SplitFire, Bosch
Plugs I dislike: Accel (cheap and blow the compression seals out on a normal basis)
Plugs I've never used: NGK, although I've heard good about them 99% of the time

I'm a fan of copper and platinum. I think all the hype with multiple electrodes and multiple anything is just that, hype. I have the SplitFires in my car now because I got them for free and they were sitting in the basement for ten years. They work great and look good but I doubt it's because of the split ground strap. If you want a good book full of interesting stuff on ignitions get the book by Doctor Jacobs from the old Jacobs Ignition fame. Great stuff in there about making a killer ignition whether it's stock to a magneto.
The biggest thing with plugs is making sure the center electrode is cut square and has nice sharp edges or has a small electrode like the platinum/iridium etc. That way the power to flash an arc across the gap is much less and there is less chance of misfire at any rpm. This is the reason for the iridium/platinum stuff. Small electrodes don't last long with high power ignitions so they make them from these exotic metals that will last longer and wear less. Also gaps in the .045-.050 range are all you need. Bigger gaps than that tend to destroy plug wires and other ignition components quicker. Also stay away from solid core wires and go for a top of the line spiral wound set or stock if that's your preference.

 

I used NGK in a mild performance built 455. I like them so far.

 

NGK XR-5, or 5670's, I've never used anything else.