Before putting the 83 d-150 away for the winter I got cylinder compression and vacuum values
compression 1 to 6 (engine warm) 120,150,150,129,150,148
vacuum: idle 19 to 20, 60 mph/2000 rpm 15, full throttle 4 to 5

this engine has 100k miles on it,I plan to take it down this spring to freshen it up. I thought the wear on the engine would have taken the compression down more evenly, or is it likely the range found is due to manufacturing tolerances? It is my thought the vacuum values are in range.
Is that correct?

thanks

Well, your at the top of the 20 percent difference between cylinders with the 120psi in the #1 cylinder (150 to 120psi from high to low). Vacuum looks good...exactly what I run on my '83 engine. The variance could be any number of things. My understanding is if you drop below 100psi on any cylinder, the rings are going. So, for an engine with 100K, it looks good. I'll have to do a compression test on mine someday to compair with yours.