Thanks, Chrome! That helps !!!
Well Gents, I spent a lot of time this weekend tinkering on the ignition; more than I should have due to my own incompetence including forgetting to reconnect the vacuum advance prior to a test drive. The test drive, of course, surprised me with unexpected results. I decided to pull all the plugs... and broke one.
Only after that did I discover my oversight and go for another test drive. This evening I'll pull the plugs again and check the coloration;
with the vacuum leak they looked a tick white but clean. No oil or fuel.
Test drive results: With the vacuum advance reconnected (no leaks);
The engine behaves reasonably well overall;
It seems to have
significantly more mid range power and throttle response; (quite impressive actually)
Mid throttle is very good. WOT, however, is sluggish.
Cruising at 60 is fairly comfortable (finally!); if loud and annoying at 2800 rpm;
The idle, at 850 rpm, has a vacuum reading with a
needle that vibrates rapidly between 20-24 in/Hg; the vibration flattens out at higher RPM. At 2000 rpm, the vibration is mostly gone with the needle stabilizing at 24 in/Hg;
The idle is generally smooth with what sounds like the occasional miss or maybe light popping in the mufflers;
The pops in the muffler get louder on deceleration during the test drive.
Ignition adjustment: Tinkering around, I settled on...
Initial: 14 degrees
Centrifugal: 23 degrees
Mechanical: 37 degrees (begins at 1500 rpm - all in by 2600 rpm)
Vacuum advance: starts at 5 degrees and ends at 14 degrees at 15 in/Hg (I positively limited the advance with a stop)
Total: 51 degrees
Other observations:
That carb seems to get quite hot. I would think phenolic space might be a good idea.
Plug wires need to be replaced; one has a very good burn in it.
The carb has yet to be tuned beyond idle. It is a bone stock Edelbrock 750 CFM. Stock rod, jets, springs, etc.
I haven't driven it enough yet to see if it remains cool at idle. For the moment it does seem to be running cooler.