The P B blaster penertrating oil did the trick on my 51 chevy 216 about 2 weeks to free it up.It ran last in 1974 that's 28 years I didn't try to start it, I removed motor and rebuilt it, runs fine now. Found 3 and 5 with the rings stuck to pistons had to tap them out with a small punch after another week of soaking them. good luck let us know how it goes.
