I have a 2004 gto engine on a stand that im putting into a 73 vega. The engine has been out of the car for over a year, bought it as a long block for a corvette back up. I removed the plugs to spray some oil into the cylinders, now the crank stops and it stops again when i turn it the opposite way.
Could a piece of carbon stop the rotation? It turned normal earlier today and i'm trying not to buy all new gaskets. Any ideas will be apreciated.

 

Sounds like something fell down inside the combustion chamber, possibly a bolt or something. That's what comes to mind

 

there has to be something more going on, If you just removed the plugs and simply put oil in the cylinders, than the engine would actually turn over easier. Dont see any way to figure out whats going on without tearing stuff down. If you try and force it you will run the risk of breaking rings or who knows what.

 

Some surface rust, built up gunk or a combination of both could stop it. Pull and inspect the heads to make sure the combustion chamber is clean and the valves are straight.

 

Thanks for the advice, and i should have replied yesterday. I sprayed brake cleaner in the cylinders that was up top when it wouldn't turn any more, then it started turning again. When i first took the plugs out some good size chunks came out. I guess it was from sitting so long.
THANKS

 

I hope you plan on removing the heads to find/fix whatever's going on.