Edelbrock carb problems

[Texasdoc]

I know this is a Holley sub-forum, but there isn't one for Edelbrock carbs...

My buddy has a 347 SBF stroker with a dual quad setup with two Edelbrock 500cfm mechanical secondary carbs ( I know, overcarb'd). They are setup with a progressive linkage - the rear carb with choke is the main carb. It hits about 20% before the front carb (no choke) starts opening. The secondaries on the primary carb start to open about 40% throttle... anyway, that's not the problem.

The problems is that when the car is cold - choke on for the main carb, it idles fine. Once the choke turns off, it idles fine at around 900rpm. However, once the car/carb gets hot after driving for a few minutes, the idle stays up at around 1500rpm. Blipping the throttle doesn't help. Pulling the pedal up does not help lower the idle back down. Putting a heavy spring on the primary carb resolves the issue but makes the throttle pedal hard to push and impossible to feather.

Any ideas? I'm thinking maybe a slightly bent throttle rod. When the carb heats up, it sticks a little. Any other ideas?

There is no rubbing of the linkage on the filters or intake.