????? Some break in and settling of the valve train I can understand, but this sure does sound excessive.
Valves pounding themselves into the seat would make the lash tighter, so that's not it.
Cam lobes could be suspect, but gimme a break, it aint gonna change as much as you describe (unless your just totally cursed and your on your way to a flat cam,,,,,nah, can't be that).
Lifters going flat all ready? Yeah right like all 16 were bad out of the box? Hard to imagine that happening!
Rocker arms are rapidly wearing on the shaft (you ARE getting lots of
oil there I hope)? Push rod rocker arm ends are "seating" or rapidly wearing out? Hmmm,,,,theres a possible area to look at. Adjustment nuts backing off? Not likely as you indicated they were tight. Valves "sticking" in their guides?
Thinking,,,,,,,OK,,,I GOT IT!!! Your not adjusting the valves using a "scientific" methodology. Your ASSUMING it's OK to adjust the exhaust valve by "guessing" it's position based on the position of the intake valve, and vice versa. That means you may not be accounting for possible cam shaft valve over lap, or are "guessing" inaccurately. This is potentially a HUGE variable that would change EVERYTIME you adjust the valves! You cannot ASSUME the exhaust cam lobe is at the bottom of it's stroke based on when the intake valve "just starts to open" or whatever. Your now at a place where you HAVE TO BE SURE.
Many of the old "Motors" and "Chiltons" manuals referenced an EXACT way to determine WHEN it was OK to adjust valve such and such. Like, Exhaust on number 3 cyl is down, then adjust intake valve on number 6 and 8 cyl, etc. etc. It's like a "matrix". You could write it out if you think about the fireing order, etc. and make your own matrix. But it MUST be written down SOMEWHERE all ready????
Watch out for the valve over lap in this equation!
Ernie
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