When the intake valve closes and the TDC mark comes around you are then at TDC on that cylinder.
To find where 30 degrees is on any damper (or any other degree that you may want to find) is pretty simple.
Take the OD of the damper and multiply that by Pi. Then divide that number by 360 (number of degrees in a circle) then take that number and multiply it by what ever degree number you are looking for.
So…7.25*3.14159/360*30=1.898
That means from the TDC mark on your damper 30 degrees is 1.898 inches. That would be moving clockwise from your TDC mark.
What I do is take a piece of tape about 4-5 inches long and make a mark on the left side that will line up with TDC. Then I measure to the right 1.898 inches and make another mark.
Take that tape and lay the TDC mark on the tape over the TDC mark on the damper. Then lay the tape out CW and where that 1.898 mark is, make a mark on your damper that you can see with a timing light and you have your 30 degree mark.
