base timing keeps advancing by itself...

Yeah I have been eyeballing the 650 avs2 for a long time, comes quite a bit richer out of the box. If my needle change (2 stages richer in power mode) is a step in the right direction I might just go ahead and pull the trigger on the new carb and start tuning that.



Reading the Edelbrock manual.. it says to go to a stronger step-up spring to cure a lean spot. Am I misreading it? Currently has the yellow (4") spring which is one step weaker than factory, put in after the new cam which produces a bit less vac at idle than stock. Also suggests this spring is just for transitions, my detonation rattle is only at 3/4 to WOT throttle and is is sustained if I hold the pedal down.

And I told you I was going to check TDC, just had to wait till the weekend when I was off work.
Cool TDC is good
The lean spot that Edelbrock refers to should really be difined as an off idle stumble. A dead spot right at the hit of the throttle.
I have tried tuning with every spring Edelbrock has and I always end up with the orange spring having the best performance. My 340 makes around 10 inches of vaccum.
Good luck keep posting