Ok, I filled three of the chunkiest, most heavily corroded cylinders with Diet Coke. I figure the phosphoric acid might actually creep down in and dissolve some of the swollen and powdery piston corrosion. I sprayed two cylinders with PB Blaster around the edge of the piston and tried to get as much as possible into the tiny oil weep holes on the inside of the piston around the rings. The other jugs I sprayed half automatic transmission fluid and acetone around the skirt of the piston repeatedly allowing a bit of time for the solution to creep down between doses. I then poured transmission fluid, power steering fluid and acetone into each piston until level with the skirt. The acetone hopefully thinned the trans. fluid long enough for it to get to the rings before the acetone evaporated. Acetone evaporates at an alarming rate.
I had hit the ends of each rod pretty hard with a 10lb sledge hammer this morning and not one of them even thought about moving. After about 2 hours of the jugs "cooking" in the solutions, I hit each rod again. This time two of the pistons moved up the jug slightly. One of them has freed up entirely, but the suction from the valve won't allow me to just pull it out. I'll wait until tomorrow, depress one of the valves with my homemade valve tool and the pistons should just slide out.
Also, the rods must have been made of some fairly hard steel, because every time I hit one the ends would shatter like glass. No, it wasn't the slag from when they were cut with a torch either. One of the shards did a number on my hand, so about a gallon of blood is in one of the cylinders. We'll see if that will help to free up those pistons.

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The nose art/aviation artist and general lunatic from Houston, Texas
http://www.jasonbarnettartist.com