You may be experiencing a case of CarburitisTweakisToomuchus.
Suggest going back to square one as delivered and making sure all is set up correctly. Based on who you bought it from, I would have to guess that the meeting blocks are set up in a pretty standard orientation and the IFR's are down low.
Maybe open up the IFR to .036 or .035 and begin the tuning one step at a time from original config. Idle slots not over exposed and base timing set to around 24-26 depending on what your motor likes at idle and floats set correctly.
Your AFR could be bouncing due to an exhaust leak somewhere, or your O2 sensor is shot/dirty.
Thanks. I agree that there are an awful lot of things to tweak, most of which interact! I may be chasing my tail, but I did start one step at a time
I'll go down the list:
Everything was set up correctly as delivered including IFR moved to low position- the problem is it was pig rich everywhere, worst at the top of the t-slots!
The idle screws are out only slightly over 1 turn with an IFR of .031 (primary) and I left the secondary alone at a pin-gauged .032, although I did plug the baseplate dribble holes.
T-slot exposure is just square on the primaries.
Secondaries are almost closed (butterflies have .100" holes in all four and I run a PCV valve).
Idle timing is 27. It could use even more but I don't want to overdo it while running vacuum advance, street driving and pump gas.
Float levels as described.
Maybe I wasn't clear - the AFR only bounces from low 12 to high 13 when I'm holding a steady 60 mph at 3000 rpm, 15" Hg. At idle it wanders a bit but that's low-rpm misfire from the overlap. During acceleration to 4000 rpm it was quite steady. So I'm thinking "spurts" due to the emulsion, or the large air bleeds?
