vacuum gauge to solve idle issue

At the bottom is my sig; click on the blue stuff.
AJ's guide to Transfer Port Synchronization
or go to the Holley site.
The gist of it is this: if you have a big-cammed engine,over about 220*, but especially as it gets over 230*, then these engines like a lot of air at idle. The typical solution is to crank up the idle speed with the curb idle screw. But this puts the butterflies too far up the transfer ports, and the idle-ports stop flowing or at the least, slow down drastically. So now you end up with a very high idle and non-functioning idle mixture screws. So then a guy might be tempted to crank in a bunch of timing. Which allows the butterflies to be closed up and restore some or most of the T-port sync. Then you get to deal with the pinging or detonation of possibly over-advanced part-throttle timing, and of course the power-timing is waaay out too.
Setting the T-port sync first, and setting the initial timing a little more conservatively, and giving the engine some bypass air instead, can solve most of these issues.This is called syncing up the Transfer ports.
Keep in mind that cams in the 220 to 230 range, and higher, can easily take 45* of part-throttle timing at 2000 rpm and cruising. And be very happy there. What that indicates is that using the vacuum gauge to set initial timing can easily get you into the 20 to 25 degree zone,possibly more. And the engine will happily idle there;and possibly even cruise with whatever other timings come in.The problems come in the transitions. And yes, at 20 to 25 degrees, the engine will seem to be very snappy from around 1500 to 2500rpm. But with the T-port sync out so far, transitioning from idle to part throttle and back, can sometimes be problematic. And of course, the power timing will be set on self-destruct until you limit it to something more sane like 34* at 3400.
BTW; I titled the guide "AJ's", but I'm sure there were hundreds of guys that figured this stuff out long before me.I just used AJ's cuz I thought it would be easy to find using the search button.And the symptoms were being posted almost non-stop, at the time I typed it out.
As a comparison; My 367 cuber run's a 230*cam and 10.75 Scr with aluminum heads. It runs just fine with 14* of initial. The idle is set at 750 or a little less. The engine will pull the 68 Barracuda(3650#),on flat level ground, down to 500rpm with a 10.97 starter gear(stick-car).The mechanical-advance begins at 1000 and by 2800 the engine is seeing 28*. But it has a slower curve from there to 3400 where the engine sees 34*. I have a 22* vacuum can which starts pulling in timing at about 12 inches and is all done by about 16inches or so. Doing the math for part throttle, it is entirely possible for the engine to be seeing up to 50* of total timing at 2800 rpm.(28 plus 22).
The point is this; very many people say that you need 18* to 25* at idle, and all in by 2500. While this may work for a race car, IMHO;this is not the hot set-up for a street engine with a cam in the 210* to 240* range.
Oh yeah, my engine has almost never run anything but 87E10. And the reason is this; I heard many years ago, that the stuff they put in "premium" gas makes it burn slower. Well to my young mind, I thought: Hmmmmm is slower a good thing? Well it is if it keeps your engine from hammering it's bearings to death.
Peace!