427 stalls when you stop

[steve meltzer]

I've got a 427 SO, toploader, new factory Holley 4160 (vac secondaries), MSD box and typical Ford distributor (from Southern). This Kirkham has only about 300 miles on it, and, based on the intake manifold vacuum, I replaced the "65" power valve for and "85". (Don't really think that's an issue here, but thought I'd mention it.) The problem I'm having is that the car stalls and dies when I come to a stop...not necessarily a hard or "panic" stop, but even a gentle stop. The RPMs dip into the 600 range, and the car dies. I know that Holleys can do that under a hard stop if the secondary floods the intake, buth this happens under all stops.

Both floats are just at the lower lip at idle...this is a little tough to discern, as the idle is somewhat rough, at about 1000 RPMs. I called Holley and they said that I need to add a "dashpot" to sustain the normal idle, but Southern (Lyle) thought the distributor springs might be weak, allowing the advance to fall too low. The timing is at 36° BTDC, all in at 3200 RPMs. I don't know what the base idle is at this moment (never paid any attention to that).

Any thoughts as to what the problem might be and how to solve it?
Thanx steve meltzer "unencumbered by the thought process"