engine flushing????

ok, ive recently replaced the valve cover gasket and when i looked through my cams i was disgusted at the shit build up of black burnt flakes over my cam bearings, locks and walls of the head. ive been told not to do a engine flush as the build up might be covering up problems that might arise when it flushes or could clog small over small oil passages in the engine body. any opinions on what i can do other than rebuilding the engine (estimated by machine shop at $1500 for rebuid) THANKS:screwy: