I pulled the 350 out of my '92 Silverado to replace the freeze plugs and to do a general clean-up. I'm on a tight budget and can't afford to do a complete rebuild, besides, the engine was running fine except for the freeze plug issue.

I'm still in the process of disassembly, but I've discovered that the crankshaft will not turn more than a half inch. I've removed the spark plugs,distributor, intake manifold and oil pan, but not the heads yet. What could be preventing the engine from turning over?

While removing the engine and transmission as a unit, the transmission fell off the jack and the engine squeezed the distributor against the firewall hard enough to mangle the cap and rotor. Could this be related to the crankshaft hanging up? It's a high-mileage engine (258,000) that had a lot of sludge under the valve covers and in the valley, but the oil pan and bottom end look relatively clean.

 

guess you may have damaged your distributor gear. you can always mark it, then pull it out and see if the engine turns.