That's just it...its runs OK. But, when I hear folks, like Mike Romain, claim their 258 "turns 52 mph in second gear" and "75 mph in 3rd gear", I can't help thinking mine could run a little better. The engine is in great shape, good compression, and it doesn't burn any oil. The plugs have the textbook brownish tan overall color, with the appropriate color change half way down the ground strap.
Well, I adjusted the vacuum canister out (CCW) 4 full turns, and it eliminated most of the low RPM detonation I was getting. I assume this moved the vacuum advance curve further to the right, making it kick in closer to the centrifugal.
The problem, now, is the Jeep has no "jump" at low speed. It accelerates smoothly, but slowly, when I step on it. I get a noticeable surge in acceleration when the advances kick in, but it's late in the RPM range.
BTW, I tried to tear apart the old Motorcraft dizzy, just to see what's involved in replacing the head in the new one, but I couldn't even get the thing apart. One of the Philips screws on top was so tight, I mangled the head and never did get it loose. Aaaaarrrrgh!!
This whole thing is really starting to frustrate me. A guy should NOT have to tear open a brand new dizzy just to get it close to factory setting.