AVS 4401 Idle Down Problem

[ChargerCharlie]

I have a 383 4BBl Charger I am in the process of restoring.  The engine is .030 over and otherwise stock in all respects.  The AVS 4401 carb has been rebuilt.  Engine is timed at 5 btdc and has an idle set around 750.  When I open the throttle and run the engine up it takes too long to come back down to idle speed sometimes hanging at a higher RPM until finally coming back down to 750.  It does this with the vac. advance disconnected as well. 

The 4401 has the air bleed screw on it with L/H threads. 

Until reading some posts tonight I was not aware that the centered L/H thread bleed screw was an air adjust and not an idle mix adjust.  It is adjusted pretty close to the seat at the moment with the expectation that it was an idle mix adjust and that this would slow down fuel feed with the primaries in idle position. 

What is the probable cause of this situation?  I have backed out the air bleed screw as well and the problem seems to still exist.   Can the idle mixture plugs be removed and the idle mixture screws adjusted on a 4401?  should I go with different emulsifier tubes (a type with more holes to lean out the fuel signal at idle?)   

Any ideas on how to fix my idle down problem would be much appreciated!

Thanks!

[myk]

Your throttle linkage isn't hanging up, is it?

[Ghoste]

Yes, the plugs can be pulled to adjust the idle screws.  As far as changing emulsification tubes in a Carter, I don't think you have that option. 

[ChargerCharlie]

The linkage is free and returns to it full shut position when actuated.   I will disconnect it again and see if there is any difference. 

AVS emulsifier tubes are attached to the primary venturis and are perferated tubes connected to that assembly.  They can be swapped out.  I had a 340 with a bit more than stock cam that needed more fuel at idle and I went to some big block venturis with less holes in the tubes which allowed idle circuit to pull more fuel at idle.   The venturis in this 4401 have two holes in the top and two holes in the bottom.  This style of tube would tend to draw more fuel at idle.  I have a set that has quite a few more holes in it that I may try.  I will first do what  you guys recommended.  I have never pulled plugs and tried to adjust idle on an AVS before.  Should be intresting.

[firefighter3931]

Charlie, before you go tearing into the carb make sure your advance weights in the distributor aren't sticking. 


Ron

[ChargerCharlie]

Thanks Ron!  Got that covered.  I had the distributor out awhile back and checked everything out.   No probs with it.  I also set the vac. advance can to react slower as the vacuum coming off the carb was pulling the advance plate at idle causing an idle speed up. 

Question... in regards to this same carb, the only vac. port on the front of the carb pulls a vacuum at idle (it connects to the dist. vac. advance).   Shouldn't there be no signal until the throttle is opened up? or is that correct?  RPM at idle is around 750.

[firefighter3931]

Thanks Ron!  Got that covered.  I had the distributor out awhile back and checked everything out.   No probs with it.  I also set the vac. advance can to react slower as the vacuum coming off the carb was pulling the advance plate at idle causing an idle speed up. 

Question... in regards to this same carb, the only vac. port on the front of the carb pulls a vacuum at idle (it connects to the dist. vac. advance).   Shouldn't there be no signal until the throttle is opened up? or is that correct?  RPM at idle is around 750.

Charlie, with regards to your question ; the vacuum advance must be connected to ported vacuum....if your connection has vacuum at idle then it could be pulling additional timing into the motor. As an experiment try disconnecting the vac advance & plug off the port and see if the problem persists.

Fwiw, i allways disable the vac advance and tune without it. The cans are designed for stock engines that pull in excess of 15hg at idle....if yours is making less than that it will cause tuning headaches. 


Ron