Getting an older, high-mileage engine TOO clean can lead to oil consumption problems. Sometimes, the carbon buildup behind the rings is the only thing holding them into contact with the cylinder walls. One thing I've used to check engines is a "cylinder leakage" test, where air pressure is put into a cylinder at the top of the compression stroke, through the spark plug hole, and listening for leaks at the carb, exhaust, and oil filler. This checks valves and rings, and can also be used for head gasket testing by looking for bubbles in the radiator. Get the cylinder close to the top on the compression stroke, lock the crankshaft with a vise grip on the flywheel, or put it in high gear and set the parking brake firmly, and use an old spark plug shell with an air line fitting brazed into it to pressurize the cylinder. Listen at the carb, exhaust pipe, and oil fill hole for leaks. Repeat the process for all cylinders. I'm going to guess you'll find pressure getting past the rings into the crankcase. Time for a ring job, or a full overhaul!
Jerry
