Ronald Weishaar
Well-Known Member
Does anyone have this engine combination? What spark plugs and plug gap are you using? On my 540 cu.in., 10.5 compression with MSD 7AL-2 ignition box, MSD Pro Power coil and Indy 440 EZ-1 heads.
That would be a lengthy process for me as it usually take an hour to pull the plugs and even longer to put them back. The gap I'm using now is.045. before at .035 it would back fire loud like a shogun going off I'm using RC12YC. the engine is in a 68 Dart and long tube headers.Years ago the way some racers set plugs was to start with a close gap, and make a run. Open up the gap .005 and make a run. Keep doing that till your time falls off. Go back down .005 to your last gap and run it there.
IF you are using the Champion RC-12YC plugs as noted, you must be running a B or RB engine....yes? USUALLY, plugs gapped at 0.045", with a stock type of ignition system (you did not specify the type), a high end end misfire could occur. Gapping the plugs at 0.035" is a standard setting. Backfiring could be caused by a multitude of issues: Lean fuel mixture, vacuum leaks, too much spark advance, faulty ignition coil, or spark plug wire(s). Sometimes, long tube headers (small bore but long length) will cause a reversion with the exhaust gas exiting pulse, causing a lean condition, leading to a backfire condition. Just my opinion of course.That would be a lengthy process for me as it usually take an hour to pull the plugs and even longer to put them back. The gap I'm using now is.045. before at .035 it would back fire loud like a shogun going off I'm using RC12YC. the engine is in a 68 Dart and long tube headers.