How to determine EXACTLY where TDC is?, Valve adjustment advice needed Options

[JeffBowlsby]

Eyeballing alignment of the rotor to the tick mark on the dizzy body seems so imprecise...for adjusting valves. Is there a method of locating TDC for each cyl PRECISELY?

1. I thought about making some kind of rotor replacement device with a pointer that could extend down close to the tick mark, but thats only good for cyl 1. All cylinders needed.

2. I thought about making a special trigger point plug adapter with three long wires, and attaching it to me DVM on the buzzer setting. When the trigger points would make contact, then that would indicate...? I am not sure that the trigger points make contact at TDC, I think it is at some different point in the cycle.

Any time proven methods?

[charliew]

My experience is with t1 bugs. It was always real easy to just pop the valve covers with the car up on jack stands a little and jam one wheel so it couldn't turn and put it in high gear. Then you could just turn the wheel as much as you want to determine the base circle of the cam on each cylinder. You don't have to roll all around under the car jumping back and forth between cylinders and maybe forget where you were in the process. The bug was so easy to rotate the starter deal was too hard for me to try and be precise with. You also get used to hearing the compression leaking past the rings as it comes on tdc. THe rocking back and forth to get centered was always easy to do. It's kinda wierd how some things are still the same after 40 years.

Oh yeah, EXACTLY means using a indicator on the piston and moving the piston either back and forth, or actually up and down, to get the exact center of the arc of the crank or running the piston up toward tdc to maybe within 20 degrees, and measuring that point with a dial indicator, marking the pulley, then going on toward down till the same amount that was on the dial indicator before, is reached, marking the pulley, then dividing the two marks on the pulley, and that would be EXACTLY tdc of the piston, or the center of the arc of the crank. But actually that is not the center of the low or base circle on the cam lobes.