1967 289 eng locked up

A little background. I recently got my 67 fastback back from a buddy I sold it to some 15 years ago. He had the trans and engine “rebuilt” by non-shop individuals. The last time the engine ran was some 8 years ago. He said it ran ruff and the only way to get it to run “smoother” was to advance dizzy and change plug air firing order. Once I got it home I thought it was 180 out. As I tried to manually rotate engine to TDC it would “mechanically lock up” before I could complete two full rotations of the crank. It stops the same spot each time. I have dropped the oil pan to ensur the new oil pump he installed wasn’t loose etc., removed the dizzy, jacked the rear to ensure no restance with trans, loosened each rocker arm thinking of a broken valve may be blocking cylinder. Since the engine will do one rotation but not two I don’t think it’s a broken valve. So what is stopping the engine from rotating two full rotations?

Well I finally got the engine to rotate only after I removed both heads. With the driver side head it still wouldn’t rotate two full turns. After I removed the passenger side head it rotated. Their were no signs of any issues such as blown head gasket etc. it’s a mystery to me. I noticed with the driver head off three lifters, two on passenger side and one on driver side wouldn’t move. I thought stuck lifter but once passenger head was removed it rotated. Wierd. Now time to reassemble.

jozsefsz said:

I'd say there was a very good chance your valves were in contact with your pistons if the pushrods were still installed on the passenger side. No way I'd re-assemble without pulling that timing cover and checking the condition of the timing chain and gears and making sure it hasn't slipped.

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All pushrods were removed. I plan on removing cam just to check it since I’m this far in. The engine was rebuilt about 15 years ago and only ran a couple hours since then. It hasn’t been driven on street in 20 years. The owner said he couldn’t get it to run right and move the plug wires, advanced dizzy. It’s in good hands now however.

Removed the driver side cylinder head no change. Removed the passenger side engine now rotates freely. Perhaps tapping the head with block of wood during removal “unlocked” whatever was the problem. Just a wierd issue.