Thanks Jerry, I don't feel so bad now, and am glad to know there is some wiggle room doing the companion method with the stock engine setup.
I didn't get to fiddle as much as I wanted today due to rain, but I did get it running smooth at low RPMs. It started bumping again around 1,000 or 1,100 and kept bumping as revs increased. Things I did today:
1. New distributor cap
2. New rotor - didn't use it because the fit was sloppy
3. Checked the mechanical advance by pushing the rotor clockwise (didn't know you could do that), and it rotated then rebounded back, so it seemed to be functional
4. Checked resistance in all plug wires (coil wire too) all had good constant resistance numbers on the multimeter
5. Checked distributor for wobble, and there was some. I could see it change the points gap, but twisting the grease cup made it feel solid so I figure that is what it's supposed to do
6. Changed the points gap to be .18 instead of .16
I wanted to confirm the dwell was right then reset the timing by vacuum today since I adjusted the points, but it was rainy and I wasn't able to go warm up the engine to do a proper adjustment.
So I'm guessing maybe the plugs themselves need to be replaced, or I have slightly sticky valves? Maybe going over the timing after a good warmup might fix things? I'm stumped, the plugs have maybe 5 hours of run time.
About my original post - I was ultimately concerned that the engine is running lean (plugs are bone white) and thought that was caused by an overheated intake due to the stuck heat riser. What else can cause it to be lean if I have good vacuum - 21hg at sea level?
