Another carb help...

[MikeB]

Originally Posted by RichardJ

I have two '69 AVS carbs. I also have a '70 and a '71 AVS that do have the EVAP port, but not one of the four have a casting provision for a manifold vacuum port for the ignition.

Well that's certainly interesting, especially based on extensive write-ups by a GM engineer and others discussing ported vacuum and why it was only needed to meet emission standards at idle.

However, both Edelbrock and Holley manuals say to use ported vacuum for ignition advance, but we've pretty much ignored them.

Last time I tried to use ported vacuum for ignition advance, I had to increase initial advance way above spec to get rid of a momentary off-idle stumble. At some point, like 20-25 degrees BTDC, that might have led to harder starting.