Edelbrock idle screw question

[69Runner]

Older Edelbrock 1405, 600cfm AVS with manual choke currently on my 440. Donor carb from another engine, it behaves the same on both engines:

At warmed-up idle, when turning the driver side idle screw in all the way, the engine will stall as expected. Backing it out restores the idle. But turning in the passenger side does not result in engine stall. Why would that happen?

I don't know whether to attempt to rebuild or buy another. Thanks in advance.

 

[Photon440]

Take the needle all the way out to ensure that it wasn't damaged at some time. It might not seat even when turned in.

Alternatively, it may be blocked all the time and the idle is running on just the driver side.

 

[The Horvaths]

^^^ What he said. You may pull each idle mixture screw and blast a little carb spray in there. Use the little red tube and wear some eye protection. If it is blocked, there is hope that you can clean it. One other possibility is that the idle circuit is not properly exposed on the one side due to a bent throttle plate or twisted throttle shaft.

 

[69Runner]

Alternatively, it may be blocked all the time and the idle is running on just the driver side.

That's what it sounds like! I went back to the Eddy carb manual to study the idle circuit. There are actually 2 idle air bleeds, maybe something up there is blocked, or at the needle as horvaths suggested. Thanks, i'll get busy this weekend checking it out.

 

[The Horvaths]

Still another possibility is that one side has an air leak at the throttle shaft or baseplate. A spritz of WD-40 at idle should clue you in to that.

 

[69Runner]

Update: I removed the passenger side idle mix screw and blasted the hole with carb cleaner (and WD40 for good measure). That must have done something because now the engine responds to idle mix screw adjustments.

While playing with the idle speed screw I moved the distributor advance hose from manifold to ported vacuum to see how it would affect idle. At 640 rpm the initial advance was zero, but it was very sensitive to the exact rpm. Adjusting the idle screw by only a quarter turn the rpm jumped to 850 and the advance to 12 degrees.

After further experimentation the best setup seems to be 10 degrees initial (achieved by turning the distributor) and all in at about 40. Now the ported vacuum kicks in when the throttle opens and it's starting and idling like a champ.