Originally Posted by lotsagrass
Sorry for all the questions. Just want to make sure I'm going about this the right way. Regarding the flywheel key possibly being sheared, wouldn't that only affect the timing of the spark since the magnets on the flywheel would be in a position they shouldn't be and not passing by the coils when they're supposed to? ...but not affect the timing of the valves opening and closing when they're supposed to? I mean, isn't the valve opening and closing totally dependent on the camshaft and has nothing to do with the position of the flywheel I'm showing below? Know what I mean? If my brain is thinking right, if the flywheel shown below is in the wrong position due to the key being sheared, then that would only throw off the timing of the spark, not the internal workings of the engine (crankshaft, camshaft, push-rods and valves). Right? Forgive me if I'm wrong and maybe I'm over-thinking it...but when I think about how the engine works, that's how I envision this working. So if the compression is GOOD (57 lbs that you mentioned is correct according to the FH770D service manual), then the flywheel key is a potential problem. If the compression is LOW/BAD, then the push-rods (bent) may be a problem. Make sense?
Everything you said is correct.
If compression is good, I would think it's a flywheel key.