crankshaft will not rotate more then 120 degrees clockwise but rotates counter clockwise without any force required

I recently had a blown head gasket before installing the new gasket I had the head resurfaced and the valves serviced. I am not a mechanic just a stubborn know it all. so after the head was installed I decided to reinstall the timing belt by turning the cam and crank one after the other not realizing that the timing would be incorrect due to my lack of knowledge. now once I did some homework on the subject when trying to set the crankshaft to TDC I was unable to turn the crank a full rotation clockwise and turning it required what I feel was too much force, but counterclockwise the engine rotates completely with normal force. I am at a standstill cannot figure out the problem of where to find the possible problem. please help