Before pulling the sheet metal and wasting a lot of time scrubbing, do a power wash first. Fill the crankcase with 30 weight bottom-shelf house brand oil from Walmart or your favorite parts store, add about 3 quarts of kerosene or Diesel fuel, and run the engine for about 20 minutes at a fast idle- - - - -1500 RPM or so. The crankshaft and connecting rods splashing down into the overfilled oil pan will work like the agitator in a washing machine, and do a much better job of dislodging sludge than any amount of brush work. Drain the oil and filter housing while it's still warm.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!