Well the damper won't rotate on the crank once it tight otherwise you can drive your alternator with it. Measure the circumference and divide that number by 360. Write it down. That is inches/degree. Set up a reference pointer and using your piston stop mark the 2 lines on the damper. Measure the radial distance between them. Take that number/the inches per degree number. That is how many degrees between the 2 mark. Measure 1/2 way this is 0 deg. (at least until the damper is removed or the crank bolt lossened) Now calculate the distance for 10&20 deg and mark it on the damper to get 3 timing marks -20,-10 &0.


51 GMC 4.2 turbo
Can't solved today's problems using the same technology/thinking that created them