Try it with the vacuum advance unhooked.  May be that at that particular rpm with no load that there is too much advance.  If everything else is OK as you state, I wouldn't worry about it.

John - "The Hoosier Hurricane"

A while back I set my distributor advance curve, but one nagging issue has led me to revisit the issue in this post.  The issue is that if I accelerate the engine in park or neutral, it will misfire irregularly yet frequently, particularly at moderate to low rpms.  It never misses while driving, but something must be wrong for it to miss under this moderate-speed-low-load situation.  It seems to happen most (perhaps only) when the throttle plates are not quite far enough open to draw fuel out of the booster venturis.

My distributor is set as follows: initial advance is 11*.

Mechanical advance is 0* at 800 rpm, 2* at 900, 4* at 1000, 13* at 1400, 18* at 2000.  Max advance is 36 but I'm not certain when it comes in because my tach only reads up to 2000.

Vacuum advance is set to 8* at 6.5" mercury, 23* at 12", and 27* (max) at 15".

Also, I should note that most of my plugs are on the lean side, some having some pinkish color at the edge of the combustion area on the insulator, others looking textbook normal.  They are all very clean, with no carbon deposits.  The carb is the factory correct unit (by serial number) with the correct main jets and a proper wet float setting.

I never experience misfire while driving, nor have I ever noticed spark knock, even when forcing a 2-1 downshift accelerating up a highway on ramp.  The engine is responsive, never stumbles, and has good power.  I just want to make sure I'm tuned right.

Thoughts?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive