I've got a 67 300 with 440 TNT engine. I'm using Champion RJ12YC plugs from Summit Racing. I asked about other heat range plugs availability from Summit but all they seem to have is the J12's. My service manual calls for J11Y for the 440 hi-po or even J10Y. These are "hotter" plugs I believe?
With Champion plugs, the higher the number the hotter the plug. I run RJ12YC's in my 440. RJ11 still show on Champion's web site if you want to try them. Do you have any pinging or knocking when accelerating? Have you had to retard your base timing to eliminate the above issues? What octane fuel are you running? One major drawback to a too cold plug is fouling after cold starts, and if the engine is older, deposits building up on the electrodes and therefore fouling hot and cold.
Thanks, don't really have TOO much of an issue with the J12YC's. It's just that a couple of cylinders in my engine have some deposits on the plugs while the others are still clean. Guess I probably need a HOTTER plug in a couple of cylinders.
Question - does a HOTTER plug result in less pinging? I know adjusting timing and advance curves etc, but will a plug also contribute to improving that situation?
Joined: Sat Mar 29 2008, 03:36PM
Location: North eastern Wis.
Posts: 1638
Ross, I am no expert, but I would think a hotter plug would make pinging worse. I use them to try to clean up the burn. It sometime cleans things up in my older junk and gets rid of contaminants. Hmmm, maybe a hotter plug could eliminate some forms of pinging. Like hot deposits in the chamber.
I've believe too hot a plug can be a cause of pre-ignition...just like the glow plug in a diesel. If you have a lot of junk in your cylinders how about running a top engine cleaner thru it a few times a year. I had a worn out RB I kept useful for a year by doing that. With 20 stuck rings it would wipe out the plugs in short order. It got a can down the carb every few weeks. It got a set of new plugs the other every few week. I was afraid to run hotter plugs for fear of detonation which would have killed that old mill pretty quickly. The plugs recommended in the service manuals were from a time when regular fuel was about octane 92. Today's premium is barely better than that.
