I just rebuilt the head new intake and carb on my slant six and can’t get it to run right it’s a super six with a 4412s on it. The highest vacum is with the idle mixture screws all the way in. I did not mess with timing or the bottom end
Ok so much wonderful help.
Assuming;
adequate valve lash, good Leakdown numbers, correct fuel-level, a clean carb, correct dwell if points, a proven TDC index, and correct plumbing of all vacuum accessories including the PCV; then
I think you just need to close the throttle and simultaneously increase the Idle-Timing, until you get a smooth idle at 3.5 turns out, (Edit for fat -fingers should be 2.5 turns +/- .5 turn), and 500/550 rpm.
If the IdleTiming gets to be excessive (over 10* IMO), go back to the Top, beginning with increasing the valve lash. I set mine to .013/.023 @ ~65* ambient.
Leave the vacuum gauge in the toolbox.
