Well.... after hours of chasing ghosts... I have finally settled on a set-up that is working nicely for our 40 degree ambient November temperatures in Pennsylvania. This may change next summer... but for others that are chasing 38/38 smooth driveability issues, the following may help:
I had started out with 135 mains, 170 airs, 45 idles, F50 em tubes - as the new carbs came from Redline Weber. These were "generic", out of the box genuine Weber 38s... ie: not ones specifically jetted for a 3.0 or 3.3 M30 engine.
Quickly found out that the top end / main circuit would just flutter and fart out at 3500 rpms or higher...so I went to work sleuthing a solution. I have loads of DCOE experience, and this both HELPED and HINDERED my approach to the 38s. It felt way too fat (you can feel the difference between rich and lean crappiness, after decades of carb tinkering) and that raw fuel was indeed dumping into the cylinders.
I set to work blocking off the tiny ports that feed the power valve its vacuum signal....and that eliminated the tablespoons of raw gasoline dumping into the motor... I used very tight fitting drill bits in the holes, with "just enough" hanging out, that if I ever wanted to remove them w pliers, I could. As my friend said: "Eliminate the power valve function and let the main jets do their job".... and he was absolutely right!
putting in smaller mains (130s) and 185 airs got the top end and throttle crispness back where I wanted it. After some more fiddling, I increased the idles from 45 to 55...and then even 60. This was in an effort to chase a lean spot during the tail end of the progression circuit. I got it to the point where you could squeeze the throttle in any gear from 1200 rpm up to redline without a stutter or flat spot... but every once in a while the car would get ornery and cough at one fairly specific throttle position. Sometimes it was incredibly subtle at highway speed... but I could feel it and it drove me nuts. My DCOE experience has taught me that fatter idles will often clear up this lean spot... but after dozens of jet changes, the lean spot still persisted. Often as a faint flat spot at cruise position throttle at highway speeds. Thinking this might just be a main jet issue after all - I installed some 145 mains and 185 airs... but the car fluttered and immediately fouled it's plugs. "Way WAY too fat" I thought.
What I missed in the above scenario - is that the plugs had fouled (somehow - and only ONCE) JUST BEFORE the 145/185 swap...and I had mistakenly thought the fatter mains had CAUSED the fouling... so I tossed in the smaller mains and another week went by until I said - "dammit... I'll try fatter mains again, because just MAYBE the tail end of the progression circuit is ACTUALLY the MAIN circuit!"
(again... I really WANTED to believe it was lean idle jets at fault - as is often the case with DCOEs)
Yesterday - one last time, before I put the car in winter storage, I tried the 145 mains again...and it was like friggin MAGIC! I ran with 170 air correctors at first... then switched to 185s....and the car runs GREAT. Next spring I'll see what the AFR gauge tells me... but I refuse to be a slave to it. As long as I'm nice and fat at full-throttle 5000 rpm and not fouling plugs at traffic lights... I'm using the AFR numbers only as a rough guide. Modern fuels yadda yadda...
Throughout all of this, I've also been toying with ignition timing a bit (while I await a custom curved Bosch distributor to come back in the mail) and with ported idle vacuum at around 7-8 degrees BTDC and full advance at about 38-39 degrees... the car seems happy as a clam in the current weather conditions. The re-curved distributor will have more radical timing at idle and should make throttle response even better...
And yes... I must have checked float levels 3 or 4 times during the last 2 weeks.
Will be curious to see what it likes best, once the temperatures come back up into the 70s/80s around here.
And adding cruise advance for a specific manifold pressure range is cool. Also agree on the dyno for maximizing it's potential, you could manually press + or - while on the dyno and watch the results then code in the curve. I'd love to do that someday when I launder enough $$$.
