OK- - - -how about a few more details? For starters, which engine are you working on? A 69 C-10 can have at least three V8's and a couple of 6 cylinders as original equipment. Six or V8? Since all of those engines have timing marks on the front of the engine, the most obvious guess would be a slipped outer ring on the harmonic balancer. If the timing marks on a good-condition damper ring are 180 degrees away from the mark on the timing cover when the #1 cylinder fires, there's no way the engine can run. On either a Chevy six or a V8, regardless of displacement, it might be possible to make an engine run with the timing marks 20 or 30 degrees of crankshaft rotation out of place, advanced or retarded, but that's about the maximum "out of time" the engine will tolerate.
There is a precise way to determine if the timing marks and the pistons are in synch, but very few, if any people on the Stovebolt forum are willing to follow the steps necessary to get an accurate check. Drop me a PM if you want some details.
Jerry
