SHELBY10001

I WENT TO CHANGE THE PLUGS ON MY COBRA WHEN I REMOVED THE FIRST ONE IT LOOKED LIKE THE PLUG WAS NOT THREADED ALL THE WAY IN, ONLY ABOUT 1/2 THE THREADS ON THE PLUG WERE IN THE CYLINDER. I CLEANED THE PLUG THREADS AND LUBED THEM AND REINSTALLED IT.REMOVED THE PLUG AGAIN AND SURE ENOUGH ONLY 1/2 THE PLUG IS GOING IN....ALL OF THEM WERE LIKE THIS. THE PLUGS ARE BOSCH PLATINUM 4, #4458. IS THIS THE CORRECT PLUG? OR IS THIS ALL THAT THE PLUG SCREWS IN? I BOUGHT A 14MM TAP AND ALL THE HEAD THREADS ARE PERFECT. ANY HELP WOULD BE GREAT..................THANKS

97targa

Bad idea to tap the threads while the heads are on the engine. Good thing they were all good because very little shavings went into your engine. I would change your oil right away!
Get rid of those Bosch Platinum garbage plugs. Get some basic copper core plugs as they are the best for perfoemance. They don't last quite as long, but they are very cheap and consistent and reliable. I am using NGK TR-6 gapped at .050" with accel coil packs and a tune. I would say you should gap them at .040" and be safe. They are one step colder than stock. I think they plugs you have only are threaded like 1/2" and you need to have the 1" threaded plugs. You will change blowing a plug out and stripping the threads if you don't have the right plugs.

SHELBY10001

THANKS FOR THE REPLY 97TARGA, THE PLUGS I HAVE DO HAVE 1" OF THREADS AND ONLY ABOUT 1/2" ARE GOING INTO THE THE HEADS ON ALL OF THEM. I WILL BUY THE NGK PLUGS AND CHANGE THEM OUT.
OH YEA GREAT LOOKING CAR................

97targa

Thanks for the props. You won't use all of the threads anyways. You can use long threaded plugs on both short and long style threaded heads, but you cannot use shorties on long threaded app's. Get the TR-6's and you'll be happy! Also, the stock heat range is just too hot for our engine's. That can create worn valve problems due to heat. The plugs are gonna be gapped at .035" but I would check them just to be sure. Open them up to .045" and see how they run. They will be much smoother than the Bosch's from cold start until extreme heat! Platinum plugs are unnaceptable in racers world because they are just not great for that use which is why we buy our cars to begin with. They are used by manufacturers to improve emissions and longer service cycles. TR55 is a stock heat range if you wanted to stick with the stock heat range. Just don't open them up more than .040". I'd rather lose 2-3hp than have detonation or misfiring problems from opening the gap too much

mills281e

+1....copper is a better conductor than platinum.

Ehmark

I dont use Bosch plugs eversince they ruined my old gt engine.The plug welded itself together.

SHELBY10001

THANKS, I BOUGHT THE NGK PLUGS AND IM GOING TO INSTALL THEM ON THURSDAY. THIS CAR RUNS GOOD OVEN WITH 177,230 MILES...BONE STOCK....