ElseWare on this site, I read the timing should be set at 18 degrees before TDC, I have read the explanation of the timing operation in the repair manual probably 20-30 times by now, and still don't feel I have a good grasp of how to set the timing. As I understand it, the distributor is held in position by the manual control cable, and rotates by the manual control cable. The manual shows a 25degree before TDC mark on the flywheel. So, when I am trying to get everything set up.....where do I start? and the 18Degrees before TDC, instead of 25, due to modern fuel, I get, but I do I establish 18degrees?

I should mention, the manual I have is for cars, 1927-1928 AA-AB. I do not have one specifically for trucks, not sure if that makes a difference or not.