The harmonic balancer for my 1978 F250 300 c.i. inline six has 2 marks cut into the back edge that looks exactly the same. I have everything out of the way now so I can pull the timing cover to check if the gears were installed & aligned properly. After this I plan to put the cover back with 2 bolts & double check for top dead center. At the start of this fiasco I found the Distributor was out 180 so I couldn't time the engine. I got that changed but still couldn't time the engine. Either way the timing is either clear above the scale or clear below the scale & when I tried to time it with the only mark I could find, (before I took the harmonic balancer off & cleaned it) when I got close to 8 degrees BTDC the truck would shake like a wet dog. I believe the timing is supposed to be 8 degrees BTDC this is a California truck according to the sticker that was on the drivers door window but the sticker that was supposed to be on the valve cover isn't there any more & the books (dumb editors think the sticker will always survive for 22 years) state refer to the sticker. If the the timing gears are ok I believe that the timing marks one of them will line up at top dead center. Any body got any ideas that will help many thanks.

Bart

 

You're not the only one to have gone down this road. It's probably your harmonic balancer. The outer ring sometimes "walks", over time, making it useless for timing. Happened to me, by about 22 deg.
Turn your crank by hand until #1 cyl is tdc. Confirm this by putting a pencil or piece of welding rod in the spark plug hole and confirming TDC by feeling when the piston is at the top of it's stroke. Then take a paint market or awl and mark the new TDC on the outer ring of the balancer in line with the timing scale. I'll bet you'll find that it's way out