Isuzu Repair: timing, pullys, keyway

Question
when i have the number one piston on top how come the crankshaft keyway is not lining up with the mark on the bottom of the motor

Answer
You most likely have not correctly adjusted your pullys on your camshaft/s. Also you must be 100% accurate on your number one valve opening and closing. I would recommend a chiltons manual if you are rebuilding your motor, they have great details on these things.