You can't find TDC accurately with a dowel rod while the piston is rocking over TDC. The piston hardly moves at all when the crankshaft is rotated 15 degrees around TDC. You need to use a piston stop to block the piston when it is a good distance away from TDC, and combine this with a degree wheel. If you don't mind your timing off by 5 degrees, you can use the dowel method described above.