Holley Tuning

If you are running an aftermarket cam, high 12's isn't too far off to get highest vacuum/smoothest idle setting. If transition is or seems a little lean(not a really bad thing unless it stumbles or bucks), that would tend to point to needing/wanting a little larger idle feed restrictor(IFR) in the primary metering block but doing so would reduce idle mixture screw turns out, same as reducing the orifice size of the idle air bleed(IAB). Check the primary side transfer slot widths and lengths, .023" is a good width and .200" is a good length for a 680 cfm carb. Try this simple test to check IFR size. Start engine and allow it to come up to temp, while in Park note the engine's AFR number, now slowly bring the RPM's up to 2000-2200 (about where main system  start up occurs) and note AFR numbers at each 100 RPM increase(also note vacuum readings at each RPM change). Idle AFR should be richer than AFR number at say 1300 RPM, 13.5-14 are good target numbers to see since there is no load placed on engine. Once in gear, you should see a 1-1.5 AFR number increase. If AFR numbers stay at or decrease below idle AFR, then an increase in IAB or a decrease in IFR orifice size or a combination of both are in order. Try here for a wealth of Holley tuning tips and experience. Hope this helps 

Check and see where in the primary metering block the IFR resides, they behave much better in the lower position(like in the older Holley metering blocks-with only 2 emulsion bleeds). When they are positioned up high, they have been said not to perform as well or as consistent since they aren't totally submerged in fuel. I'd say .001-.0015" increase in IFR orifice size should help . When I first started tuning my Holley's, I had a 770 street avenger and was lean on transition, I found going from .032" to .034" IFR did the trick, just that change in orifice size was an air/fuel mixture increase of 11.5%. Looking at your notes, the AFR numbers steadily go leaner, so there may be a mixture of IFR change as well as a reduction in IAB size. Really whichever is easier to do would be my first step(probably IAB, drop .002-.004" in size) then adjust idle fuel mixture then see where numbers end up. Really it is best to give the engine what it wants and not try to hang onto a specific number-I was guilty of this during my initial tuning. 

On my metering blocks I drilled the lower IFR feed and tapped for 6-32x3/16 brass set screws, I used pin drills to make my own custom sized IFR's, I actually did the same with air bleeds-(used 8-32x 3/16" brass set screws), emulsion bleeds, power valve channel restrictors, transfer slot restrictors in main body. That said, you could take a piece of lead-like a piece of fishing weight and swedge it into the IFR you currently have with light taps of a hammer and a nail set, then drill it out with a pin drill to .033-.034"(I believe .036" would be too large) or use two-part epoxy to fill the IFR bleed's orifice and drill to size once hardened, but this usually takes 24 hours to occur. You could also purchase the larger .036" IFR and place a small piece of wire to reduce the overall orifice size for initial tuning reasons but not a good idea for long term use, I have seen and/or heard where a typical copper wire starts to deteriorate and could cause other issues if left in place. I would probably reduce the idle air bleed size to .065-.066", this should allow progressive richness as rpm's rise. You could try to place a .023-.024" piece of wire into the idle air bleed and long enough to bend over the choke's air horn with apiece of electrical tape to hold into place while checking AFR numbers-yes you can drive it this way for a short period of time. This should reduce the IAB orifice are size to around .065-.066" and verify if the AFR #'s are heading in the right direction for your needs. Do only one mod at a time of course, just to see how engine responds. Many magazine Holley tuning tips are incorrect about power valves, with a good power valve diaphragm and gasket installed, they will not supply fuel at idle even if your engine only produces 4" hg at idle with a 6.5"hg PV installed. The power valve enrichment system will only supply fuel enrichment after the main system's startup. That said, an earlier opening PV(8.5" hg.) will provide fuel enrichment sooner, if you feel you need additional enrichment you can enlarge the power valve restrictors located under the power valve. When tuning my Holley's, I try to get cruise AFR #'s as lean as possible without a surging issue(tuning combination of air bleeds, IFR's and main jets), then choose an earlier opening PV (like a 10.5") and tune my WOT #'s with the power valve channel restrictors, to keep WOT #'s around 12.5-12.8 AFR. As far as tuning the secondary side, I would wire the secondary throttle blades closed or rather to secondary throttle blade screw stop, so they will not interfere with primary side tuning. Once you get primary side "right", then secondary tuning usually becomes much easier. Hope this helps.

I purchased my pin drill bits off of Amazon and/or Ebay, get a couple of sets at least since they will not exactly match O.D. they tell you they are. I have purchased around 10 sets of them due to minute variances in O.D. size. Here's an example: Mini Drill Bit Set Index 61-80 Set of 20pc | eBay

Vince, unless I missed it, have you posted initial and total mechanical timing numbers? I realize you have probably already ironed this out but I'd make sure the ignition timing is all figured out, both initial, WOT and the progression in between the two before any more carb tuning-I should have stated that prior to a screwdriver or drill bit was used. That said, .0336" IFR is getting close to a stock 3310-1's .034-.035" IFR size, that with a reduction in size IAB's you "should" be getting sufficient fueling at idle and just off idle. Reducing IAB's from 70 to 67, you should have seen a .5 or so "richer" AFR change. Are you running a carb spacer? I found on my 472, that using a 4 hole spacer gives the venturi's a bit stronger signal as compared to an open spacer-I found almost a 3/4 point of vacuum change just by exchanging the open spacer for the 4 hole spacer. Do you use squirters with tubes or the standard shooter design, the tubes seem to help atomization due to the accelerator pump shot hitting the booster and/or allowing a more centralized fuel shot into the venturi. SMall changes can be made without using a drill bit, just raising the primary float a flat to a half turn will richen the carb at idle, transition and allow a sooner main system start-up. Have you double checked the transition slot lengths as compared to throttle blades and/or how much of the transfer slot is exposed at idle, sometimes one is higher than the other, requiring a little tweak with a file or a throttle blade adjustment(way more involved).      

Just to add. 

Welcome!  My last setup was pretty close to good.  I upped it to 68 jets and it was too rich overall, so the 67 seems to be the sweet spot for my setup.  The only other change I have made since was I upped my squirter size.  It's running pretty well overall, but I haven't played much around with the car since it is as I said pretty good.  No issue with the lean transition off idle anymore, but I do have a bit of a lean situation when at cruise if I get on the gas a bit but not hard enough for the secondaries to kick in. This was why I upped the squirter.  I have some time off this summer and hope to do some more fine tuning and will update then.  I got side tracked as I pulled the transmission to change the torque converter and then did a few other little jobs on the car.

They are set as close to squares as I can visually see.   The secondary slot is approx .020 higher so those you do not want exposed at all.   If they are your idle is very rich.    I can get rid of that lean spot that you had (and I have) by running a richer idle (around 12:1 or slightly richer) but I hate running the idle that rich.