Somewhat off topic, but ...

If you ever remove the flywheel from a Chevy or GMC engine that has the timing mark on the flywheel, take a few minutes to mark the flywheel with timing marks for cylinders 2,3,4 and 5. Makes it easy to find TDC on any cylinder.

Picture below is of a 270 GMC flywheel I marked. I used some white paint on the already marked

U|C ○ 5

symbols marking TDC (U|C) and the BB in the red circle. That is TDC for cylinders #1 and 6 shown in the red oval.

Then I used a cheap ingraving tool to mark the TDC line (shown in the yellow circle) for cylinders 3 and 4, 120 degrees CW around the flywheel and added some painted dots for visibility.

And finally I marked the TDC line (shown in the green circle) for cylinders 2 and 5, another 120 degrees CW around the flywheel with added paint.

You can get to the proper places for the marks by either:
counting teeth - same number of teeth between each mark - number varies with total tooth count
or
using a ruler to measure from the U|C mark to make an equilateral triangle.
Attachments
flywheel tdc markings.jpg (104.27 KB, 30 downloads)

Last edited by Bill Hanlon; 09/22/2026 9:03 PM.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.