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Have a 1966 F100 with a 352. Timing marks on lower pulley are not numbered. There are 4 full length marks thus divided into three sections. There are four shorter marks between each of the full length marks. Can anyone tell me how to read the marks?
Also there is “A 10 C” stamped to the left of the marks. There is a small something between A and 10 but I can’t make it out. Know what this is?
I would not trust 50+ timing marks in general. Your safest bet is to find TDC on #1 compression stroke. Piston stop is the second best option (first would be to pull the head ), Mark TDC and get a timing light with adjustable timing. This way you keep the markers (TDC and engine marker) aligned. You could also buy timing tape, just verify your diameter and TDC.
Likely the "10 C" that you see is "TDC" which would be 0° and the first full length mark. The next full marks would be 10°, 20°, and 30°
You can verify if correct with piston positioned at TDC of compression stroke.