Jegs sells a TDC tool for about $9. It screws into the sparkplug hole of your #1 cylinder. You turn the engine in one direction *BY HAND* until the piston hits the tool. Mark the harmonic damper at that spot. Then turn the engine the other way *BY HAND* untill it hits again. Mark the damper at that spot. Then find the spot on the dampner that is exactly between your two marks, and that is top dead center!!!
You can thank me later
Ed