I have a sbc 305 in my 81 malibu and it was running ok before I decided to replace the timing chain for a gear drive. the timing was off anyway. its been sitting outside without the timing chain for a month or 2. Today im ready to get this baby running again. I bought a proform tdc tool which goes into the spark plug hole. i took my breaker bar and put the proper bolt into the crankshaft.i proceeded to turn it clockwise. i felt the crank stop so i thought it hit the tdc tool. i removed the tool and turned the crank some more. it woldnt turn, so that means it wasnt hitting the tdc tool. it was just stopping. why wont it turn anymore? do i have to remove the cam, rockers or anything in order for it to turn over? Please help