Originally Posted by K and K
Pulled the valley plate on a 57 Caddy 365, I knew I'd find sludge but not this much...
Ahh, yep! Really common engines tended to run too cold back then like 140-160 degree thermostats were the thing. Oils were not as refined as they are today having a lot of stuff that mixed with crankcase water vapor, and the lead and bromine in the fuels to make this stuff, then not changed often enough. Even the detergent oils of the 1950's, 60's and 70s weren't good enough to prevent sludge formation. Many people wouldn't run detergent oils, as has been said the introduction of detergent oils to already sludged up engines loosened enough of that stuff to were it circulated either plugging the the intake to the pump or if missed by the filter some small but important feed hole, rockers probably got the worst of it nearly everybody and especially the Ford Y block had top end oiling problems. So detergents got a bad rap from doing what they were intended to do to sludged old engines. Starting with a new engine and detergent oil wasn't a problem but if the engine had many miles and only non-detergent oil in one was better off to stay with the non-detergent oils. With road draft tubes for ventilation, engines that saw a lot of in city driving had bigger problems than highway driven vehicles since they didn't get warm enough to drive the water vapor out nor driven fast enough to suck the vapors into the passing air stream so they filled up on blow-by venting only excess pressure from the tubes rather than drawing clean air in one end and venting the gunk from the other.
Yours is really a case where the engine needs to be cleaned by removal from the car and partially disassembled to clean it. Loosening this stuff in place risks getting chunks into circulation with the oil. If the engine holds good compression I wouldn't pull the crank, rods or pistons out. But I would pressure wash and well flush the crankcase with a solvent. Usually the upper parts of the crankcase are pretty clean where there is a lot of oil wash from operation. The ugly places are what you already see in the rocker boxes and valley. The other really icky places will be the timing case and the pan.
Once clean reseal it and put it together and drop it in the engine room.
Everybody, well us older guys at least, have stories about this stuff gone wild. My personal favorite was a guy that came in the shop complaining that after he drove for 15-20 minutes his Chevy V8 lost all oil pressure and when he allowed the engine about an hour of rest, when restarted the oil pressure was back, then the cycle repeated. He went on to say that when the oil was checked at pressure loss the pan would be empty and after that hour it would be full again. Pulling the rocker covers, I should say once I fought them off, and pulled the intake; one could see that the sludge had nearly closed the oil returns. The rocker covers and valley filled with oil finally lowering the level in the crankcase to where the pump had nothing to pump. When shut down for an hour the oil would finally drain back and everything would appear normal in the pan. I treated this as I describe above using Safety-Kleen which is less of a fire hazard than most other solvents and we had plenty of it at the shop. The heads, rocker covers, inside of the intake, the timing case and pan were cleaned by first scraping and scooping, then solvent washed. Wiped it out and dried it with lint free towels, replaced the timing set, seals and gaskets, lubed the cylinder walls and bottom end with a spray of Marvel Mystery oil (just love the fresh mint smell) put in the car, filled with oil and fresh filter and fired it up.
The owner had never changed oil only topped it up when needed which is how he got into this problem on the extreme edge of the sludge issue.