tune up
It seems to smooth out above 2000 rpm
This is about where your vacuum peaks and so reversion has ended, ergo all the air entering the engine is now going in the same direction. If that air has the correct amount of fuel in it, then smoothness is the result.
I ran that 292/509 cam in my 367 SBM, and as I recall, the intake gets all messed up at idle. The 108LSA version that I had gets real dirty at 750/800 idle.
So you gotta start with a proper Transfer slot exposure and plenty of idle timing, and a loose convertor. On my 3310 I had to drill holes through each of the primary air-valves to give the engine the air it craved. But be careful, if the holes get too big, the idlespeed will be too high. The secondaries need to be closed up tight but not sticking.
My best guess is to make the exposure a little taller than wide, then don't move the idlespeed screw. After that, you will be setting the idle speed with idle air bypass and idle timing. I suggest one hole in each primary valve of about 5/64 or 6/64, that is .078 to .094. The hole should be on the transfer-slot side and about half way from the throttle shaft to the edge. I bias them towards the idle discharge ports.
And I suggest
a start point of 14* idle timing with the 5/64 holes. If the idle speed is still too slow, with an automatic and hi-stall, you can increase the timing to say 18/20. If still too slow, you can go back to 14* and increase the holes to 6/64, and start over on the timing. My Eddie-headed, 11.3Scr, 367 cuber, I got a nice idle at 700/750/14*/ with 5/64 holes. If your TC drags the engine down more than 75/100 rpm, you will have to compensate for that. If your mixture screws are out more than 1.5 turns then increase the transfer exposure slightly and put the mixture screws back to 7/8 turn
The above assumes the V-can is hooked to the sparkport and the PCV is working off the front of the carb, and that the indicated TDC on the damper has been proven to be true TDC, and that the valves actually do close at some point.
After this is done, you may have to rework your power-timing and rate of advance.
If you drill holes that are too big, don't panic! you can chamfer the holes on both sides, and drop a solder plug in there, a little bulgy on both sides. Mine have stayed in there since year 2000, and well over 100,000 miles. Then move over to fresh metal and start over. .125 will be way too big. 7/64 (.109) will also probably be too big. So stick with the 5/64 as long as you can.
These mods should dry up your idle fuel, without introducing side-effects.
