Use an engine de-greaser such as Gunk. Spray it in the area and let it sit for a few minutes, then repeat. Do this 3-4 times, then wash off with a blast of water. Should clean it up well. Might have to get a brush in there to stir it up for the hard, caked on stuff. Some folks use diesel fuel, too. Just be sure to do it in a place where it won't run off into the ground water table....
I don't think WD-40 will do the job, but who knows....give it a shot and see.
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Joel Adams
C3VR Lifetime Member #56
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"