Stumble off Idle

[LAA66]

 Had the Challenger out recently after sitting most of the summer. It seems to have developed a miss while feathering the clutch that I don't recall before. Added 8 gallons of new fuel to top off the tank, other then that it is as parked in June. The plugs are clean and light colored and would seem a little lean if anything. Any ideas?

 340w Holley 650DP, Mopar 484/284 cam, FBO ignition 12 initial, 35 max. w/vacuum advance.

[footin70rt]

Two things that come to mind are the accelerator pump or debris in the transition ports. Holleys aren't much for sitting and letting the fuel dry out in them. If it's just coming off idle with very light throttle I would suspect something in the transition circuit. If it's been over a year since you've had it apart I'd pull a float bowl off and see if you have any crap in there, may be time for an rebuild.

[LAA66]

 Yes it's with light throttle. I will clear if I rev it and load the driveline hard. Suspected the accelerator pump also. There is some new puddling of fuel on the (exterior) manifold under the secondary throttle shaft too.

[Chryco Psycho]

where is the vacuum advance connected to , FBO tends to tell people to connect them wrong , it should connect to the right  side of the carb high up on the front metering block

[LAA66]

 As a follow up, I replaced all of the valve springs (along with a single broken one) and the stumble is gone. Also the idle went down without any other changes. It seems the spring may have been weak for a while before finally giving notice. Thank God it didn't happen 2 hours from home on the Big Sur coast, with no cell phone service, and my wife in the car.

[Chryco Psycho]

 

[footin70rt]

   Glad you found it.