[Excaliber]

I had a similiar problem with mine, particularly the subtle "stutter" you mention at cruise speed and also the off idle stumble.

For off idle stumble I finally (due to input from CC members) increased my base timing to 15-18 deg. I was SURE that was to much, but man it really "woke things up" and was a HUGE over all improvement. For the stutter I slowly (several times) increased the main jets (yeah FOUR of them with twin carbs) until the stutter went away. I wound up with 72's. But I STILL had a hesitation on accelleration at speed. So I took a vacuum reading at idle AND at cruise rpm and installed a power valve 1 or 2 points BELOW that vacuum reading. Again I had to try different power valve ratings until I "nailed it". I can actually FEEL the power valves kicking in with just a slight increase in throttle, like going up a hill or passing. Myvacuum was 11" and I think my final PV rating was 9.5.

No stutter, no hesitation! It was all about timing and correct carb settings. The fuel air idle ratio screws didn't seem to help much for the above problems EXCEPT for the idle itself. I'm out about 3/4 turns I'd say. REDUCING the main jet size cleared up the "loading up" problem while setting at a stop light AND the stutter. The PV is really a MAJOR player in the Holly carb.

My linkage opens BOTH primaries at the same time, there is no "progression". The secondaries are vacuum. I played with the "pump shot" but like the idle screws found that they didn't change things "that much". More advance was the real ticket!