How to unseize a 1983 350 v8 motor?

i have a 1983 chevy truck and was trying to get it running .. we had it turning but it was just not firing but it was turning slowly ... and then i changed the starter a week later and went to start it and it didn't turn .. i tried turning it by hand and it wouldn't budge ... any one got a solution? i don't really want to take it all apart but i will if necessary.How to unseize a 1983 350 v8 motor?
Marvel mystery oil in cylinders has worked for me before. Once it starts to turn work it back and forth slowly until you make a couple of full rotations. If that doesnt work,do what another poster said and pull heads. You can use a block of wood on top of piston and TAP not beat with a hammer. Sometimes this will give it that little extra it needs. But yeah the turning earlier part is odd.How to unseize a 1983 350 v8 motor?
Hey man If i were you i would pull the heads and pour marvel mystery oil into the cylinders and just let it sit for a day and do it again for a day. Try turning it over by hand to see if it frees up a little. Also take out all spark plugs that will allow you to turn it easier by hand. It will still be hard to turn over just because you are turning 8 pistons!

good luckHow to unseize a 1983 350 v8 motor?
That happened to me, same motor but in a boat. I poured mystery oil into the spark plug holes and turned it with a breaker bar after a day. A little at a time. It will go.

The fact that it was turning a week earlier makes me wonder though.