FIRST-TIME TUNEUP COMPLETE!
I adjusted the valve clearance on a COLD engine by adding 0.005 to the recommended clearances (Volfandt, interesting that you've found 0.002 might be better on a 216/235. Maybe for extra credit I'll look at the tips of the rockers). I'll readjust valve clearance after I can take it for a spin and warm it up.
I have now set the ignition timing, adjusted valve clearance, and installed new spark plugs (and adjusted idle speed and mixture, with the aid of the tachometer built into my new timing light). She sounds really good, although I maybe should refer to the truck as a "he", because the new glass-pack muffler has revealed some cajones in the old boy!
I wish I had made an observation of running smoothness after each tuneup operation, but for various reasons, mostly impatience, I did not. As a purely academic exercise, I'm going to assign the following percentages of "contribution to better running":
New spark plugs - 60% of the improvement. The old ones were highly fouled. And because the windshield wiper vacuum hose had been open to atmosphere for about 5 years, I gather that I had too much fuel to the plugs.
Set ignition timing - 30% of the improvement. Before the operation, the octane selector had been set to 8 degrees retarded, and the BB was about 1 inch to the left of the pointer. I set the octane selector to 0 and set the timing.
Valve clearance adjustment - 10% of the improvement. On this cold engine, most of the exhaust valves were fine without adjustment, though a couple had to be loosened. and about half of the intake valves were too tight. None was too loose (needed to be tightened).
The above is just a hunch. I'd be interested in ya'lls comments.
