Hmmm......it's been a long while, but seems like to find TDC, you'd thread that brass bolt into the spark plug hole (I used to braze a piece of brass into a broken spark plug) and turn the motor over gently till the piston contacts the bolt. GENTLY ! ! ! Mark the damper at the TDC arrow on the block. Turn the engine backwards till the piston contacts the stop again. Mark the damper again. !/2 way between the 2 marks is exactly TDC. Did I remember it right ??

Lar.