[Gaz64]

Rune,

Does the intake have any form of inter-runner balance?

What engine rpm does your mechanical advance start at?


Let's say the average manifold vacuum per cylinder at idle is 12 inches, rev the engine up to say 1500 and now on decel the vacuum climbs to 18-20.

The idle circuit now flows hard (more air/fuel) and in combination with possibly more timing at 1200 gives you the hanging idle.

6 vacuum gauges (highly dampened, meant for motorcycle multi carbs) will help you, plot the timing as the engine comes back.

Also fairly common for highly tuned engines to take a little to come back to "idle" depending on cam profile, intake, number of carbs etc.