[Doug Rodrigues]

Well, I don't know how many miles is on your engine, but there comes a time in the life of every engine to where it just has to be taken apart and the whole thing boiled-out in a hot tank. Perhaps your engine's time has come. Only so much can be done with off-the-shelf "treatments" and mechanics tricks. Interesting how some engines remain clean all through the years and some get gunked-up? I suspect that additives such as STP are a major cause of that gunking, since most engine manufacturers say NOT to add anything to the oil.

Of interest and humor: With airplane engines that have stuck valves because of carbonization....some mechanics do what we call "a Mexican Valve Job." The piston in the cylinder with low compression and obvious hissing out the exhaust pipe when the cylinder is pressurized with air at exactly top dead center confirms the leak. Someone holds the prop to keep it from kicking-over while the air hose maintains pressure in the cylinder. The pressure also keeps the valves tightly closed. The exhaust valve keepers and springs are removed. The air pressure is relieved. A 1/2 inch drill is attached to the exhaust valve stem and the valve is spun and pulled into the valve seat. Any carbon is quickly worn away. The drill is removed. The cylinder is again pressurized to maintain the valve in a closed position while the springs and keepers are reinstalled. In most cases, the compression on that cylinder is raised back up to normal! Sounds like a backyard mechanic repair, but it works! I even did it on an old airplane I used to own. Never had a problem with low compression after that! Never tried doing this with an automobile engine though. I suppose that one could hold a wrench on the crank pulley bolt to keep the engine from turning over.

I forgot to mention: The above techniques using kerosese or water don't remove sludge from the intake system. It only removes carbon from the combustion chamber.