I pulled the valve cover off and found a horrid mess. Seems like a bird or rat's nest. Not to mention a ton of sludge.
i had the same issue with my 40's 228 minus the nest. i asked the same question as to what to do on another truck site. it was basically 50/50 as to either leave it alone and flushing it with diesel fuel. ken (crenwelge) said that the trap on the gm engines was behind the side cover. curiosity got the best of me and i pulled it off. the sludge fell off the cover in sheets like a melting glacier in summer. prior to that i was just going to leave it alone since it too was running fine at the time but now i commited to clean. what i did first was to pull the oil pan and slide a big catch pan under the engine. i then removed the rocker assembly/pushrods and methodically cleaned off the top of the head starting in the front and worked my way to the rear. i stayed away from the valve springs but cleaned as close as i could without disturbing anything on or in the springs. i then went to work under the side cover and cleaned everything from the top to the bottom which some of the sludge got washed down the oil return holes back to the catch pan. in the process i only pulled one lifter at a time and cleaned there and in the lifer bore. then i washed off the cam lobes. when everything was cleaned from top to bottom i took the rocker assembly apart and cleaned it all up and that is simpler because i did that behind the garage. i pulled the plugs out of the end of the rocker pipe and cleaned that like my rifle. when it was all cleaned up i put it back together and filled it up with oil primed the oil system spinning the pump with my drill ensuring oil was goingwhere it was supposed to then and ran it. some said that i wasnt going to get 500 miles on it before it attacked it. when i pulled the engine this past fathers day i had around 4000 miles on the engine since cleaning it up. the engine still runs and the reason i pulled it is becasue i swapped the 228 out for a freshly rebuilt 270 or i would still be running the engine in the truck. i used no diesel or kero to clean the engine. i used a boat load of make up pads a woman uses on her face. a box of q-tips. couple of cans of break clean and an array of putty knifes, flat headed screwdrivers and a small pick. remove all the heavy stuff fist and then went back with the brake cleen and pads. i DID NOT touch any horizontal oil galleys only vertical ones that anything busted loose was free to fall or be washed into the catch pan. while you have the oil pan off remove and clean the oil pick up screen. after a short run with new oil i drained and strained the oil and got rid of any gobs that may be have been left behind and looking for any signs of metal. my engine had no filter on it when i did this nor did i add one after the cleaning. it took me three days of dedication to do the whole cleaning. since pulling the engine i pulled the side cover to inspect it for dirt and it looks as though i just cleaned it yeaterday. my concern using diesel is that it could loosen up a chunk and have it break free later thus causing a problem. if you have another engine or one in mind then just remove the bulk of the crap off without touching anything else and have the other engine rebuilt and have fun and run this engine until the rebuild is complete and then swap them. i did this twice this year so far with my dump and my 40 and the only down time i had was doing the actual swap.
