Harvester,
Thanks for the methodical approach, I was kinda bouncing off several walls and not getting anywhere. To your questions: Vibration occurs when truck is standing still. Clutch not engaged in/out of gear doesn't make a difference. I think I can rule out transmission and beyond at this point. I did not have the flywheel balanced after resurfacing but I need to check with the maching shop to make sure.
Vacuum advance appears to work but I'll pursue your thought process when I get back to it. I do have a vacuum pump/gage to see if the mechanism is leaking, good idea.
What a time I had rebuilding the carburetor. You are right, I even found a ball in a place where one doesn't go. When I finally understood how the accelerator pump actually works, I was able to get springs, balls, and things in the right place. I verified operation of the accel pump after I rebuilt it but will check that again as well.
I put a dial indicator on the flywheel trying to detect if something is bent/warped. If I kept tension forward on the flywheel while slowly turning it, the readings varied less than 20 ten-thousands (.0020) at the outer part of the flywheel. I thought that was pretty good. However, at one location in the rotation, the dial indicator took a dive and I actually heard a klunk (more like a thud) from the lower end of the engine. That was repeatable. I suppose it's time to pull the pan and see what that is. Do you concur?
So let me ask your advice about moving to the 235 I have sitting behind the shed. It's from a 59 Chevy and should bolt right up after a rebuild. I'm into this clutch/flywheel (new ring gear too) thing for about $300. If I thought I could get a smooth (I understand the technology is not 21st century) running 216 I'd put my time and money into it but I'd probably have an easier time rebuilding the 235 and I could still drive the 216 until that was finished. I'm just thinking out loud but would like your take on it.
