Bill
What octane fuel are you using? By increasing the bore (slightly) and decking
the head and block you may have raised the compression ratio just enough to
cause dieseling on lower octane fuels, particularly if the head/block had
already been decked on a previous overhaul.
Also I believe dieseling may be caused by the engine running hot like your
plugs suggest, and this in turn can result from the mixture being to lean. You
may need to get the carb rejetted - I had to do this after changing the cam in
my Brock Commodore.
cheers
Vic Hughes
william.lewis@ucdmc.ucdavis.edu wrote:
> Since rebuilding my motor, I have had a problem with dieseling. The timing
> is set at 4 degrees BTDC. I can set the idle down to 500 rpm and turn the
> idle mixture screws down so that the engine misses, but the dieseling still
> occurs. When I pulled the spark plugs, they looked like they were running
> hot. The motor went from 20 thou to 30 thousand over. The head was ported
> and the cam ground to a hotter grind. The head and block were both decked.
> A friend suggested that I may need colder spark plugs to prevent the
> dieseling. Sounds like a good theory. Does anyone know if this will work?
>
>
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