I bought a Junkyard Hemi (for my Desoto) and several of the pistons were frozen solid. They had rust curving up to the cylinder walls!! I tried every remedy I heard about: Marvel mystery oil, kerosene, heat... and they wouldn't budge. Well, I was talking to the machinist who did the work on my 248 (50 special (43)) and he said "Just put a little coke on it!!" I tried this. No special technique mind you, I just filled the cylinder and let it sit for about 15 "FIFTEEN!!" minutes and I was able to break all the piston free with very little effort!! I actually used Walmart cheap cola but you won't tell anyone will you?