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--></style></head><body lang=EN-US><div class=WordSection1><p class=MsoNormal>Bob</p><p class=MsoNormal>Like many old timer Healey folks I have been messing with these beasts for more than 50 years. Every time I had a diesel problem with a personal or customer car it turned out to be one of these things. Accumulated crud on the top of the piston or a slightly burned valve or ignition timing off or air leaks around the intake (rare) or bad gas (low octane gas). You can check the spark plugs while your at it for evidence of an overheated plug. If your concerned about high compression make sure all these other items are in good condition. I run 10.5 to one compression in my 100 on premium pump gas and no fuel additives. </p><p class=MsoNormal>Perry</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>> No, I haven't stuffed a Cummins 6-cyl in my BJ8. But, my car has </p><p class=MsoNormal>> started dieseling--aka 'running on'--more than it used to. Compression </p><p class=MsoNormal>> is high-180PSI give-or-take on all 6--but mixture is good (I think) and </p><p class=MsoNormal>> idle is usually around 700-750RPM depending on conditions. Timing is </p><p class=MsoNormal>> spec (15deg BTDC@600RPM, vacuum advance disconnected and port on carb </p><p class=MsoNormal>> plugged). I've always run Champion RN12YC plugs, and have never had a </p><p class=MsoNormal>> problem with them, but I'm wondering if colder plugs might help.</p><p class=MsoNormal>> </p><p class=MsoNormal>> Thoughts?</p><p class=MsoNormal>> </p><p class=MsoNormal>> Bob</p><p class=MsoNormal><o:p> </o:p></p></div></body></html>