Well, you've definatly got me thinking your way about this. I've been in contact with Edelbrock and Lunatti... Edelbrock says all their carbs use the same idle circuit jetting so since we know that you and other guys have run cams bigger than this on other edelbrock carbs, this isnt a problem with this model of carb with too big a cam.
Lunatti seems to think that the cam should make around 13" of vacuum so you guys have talked me into the conceeding that I've got a vacuum leak.
I've done the thing where you spray carb cleaner around looking for a change in idle speed and didnt find anything. So I remember haveing issues once with some hyd. lifters so I checked that out. Even though mine were only preloaded 1/4 turn, by backing them off just to the point of zero lash and a hair more i've picked up 1-2" of vacuum so I'm at 9-10" now... This is with 20 degrees initial advance + 15 mechanical and around 40 degrees at 1000 rpm idle with the vacuum advanced hooked up to manifold vacuum.
So I guess now I'm looking inside the motor to see if maybe a valve is not sealing or if I've got a gasket leak on the bottom of the intake where it seals against the head. What do you think?
Originally Posted by F-BIRD'88
Your carb is a leaner version of mine (Edelbrock 1407)
Do you know the drill size of the idle feed restriction and idle air bleed? mine is plenty rich at idle and off idle.
What happends when you position your carbs throttles as described in the article and then add a little fuel manually by dripping a bit down in the carb while its running at this high idle point? Or just choke off some airflow with your hand.
Does the motor pickup rpm briefly before dropping off from retricted airflow?
I still think you have a vacuum leak. Do a cylinder balance test. Find what cylinder drops the least rpm when it is disabled (spark) temerairly when the throttle is open to the troublesome off idle point.
You want to eliminate all possible faults before ya start drilling cause its hard to reverse those mods. Can cause you to loose your whole tune if you mess with the basic idle circuit tuneup to cover up a simple vacuum leak fault.