Where is the "air screw"?

[GsxrMike]

I am going to try to adjust my idle later today because it is SUPER rich and idling very low. I've read the instructions >

IDLE MIXTURE​

The Edelbrock Performer Series carburetor has conventional Idle Mixture Screws (IMS) that provide a leaner A/F when turned clockwise and richer A/F when turned counter clockwise.
The idle air flow is controlled by a conventional screw that opens the Primary Throttles. The following procedure should be used to set the idle mixture and speeds.
1. Fully warm engine and ensure choke is fully open.
2. Air cleaner in place.
3. Set desired speed with the air screw.
4. Adjust the IMS on ONE side to get the maximum possible RPM.
Do not go rich beyond the maximum speed point.
5. If the above changed the idle speed more than 40 RPM, then readjust the speed.
6. Adjust the side OPPOSITE of that in Step 4 to get maximum RPM.
7. Reset the speed.
8. Carefully trim each IMS to again get the maximum idle RPM.
9. Go leaner just enough to get a 20 RPM drop in speed.
10. Reset the speed to the desired RPM.
11. This is a Lean-Best Idle Set. Setting richer than this will not
improve idle quality or performance, but could tend to foul plugs.

#3 says Set desired speed with the air screw.
I can't find it in the manual.​

 

[Kenny78]

I believe that the air screw is the throttle screw, the screw that determines how open the primary throttle plates are

 

[GsxrMike]

Alright I will try that, THANKS!

 

[Hogback Fabrication]

The air screw sets the idle mixture and is a different screw than the one that sets idle speed (which is the one kenny78 mentioned).

 

[Kenny78]

I reread the online owners manual and am fairly certain that I am correct. The mixture screws are called IMS or idle mixture crews. FWIW, the way I set the idle on my edelbrock was as the manual says. When it says air screws I adjusted the primary stop screw. Thats all I could come up with when I was tuning mine.

 

[GsxrMike]

Yeah thats all I see. I have another question. The IMS don't seem to be doing anything. I don't have any vacuum leaks and I am sure. If I set the "air screw" to set the speed I want (800rpm) then the IMS don't have any effect on the rpm, or vacuum on the engine (I can turn them both all the way in and nothing happens). I did notice that the plate that blocks off what I belive is the secondaries is slightly open and if I close it by hand the engine dies. I am going to go down and tinker with it a bit more.

 

[Kenny78]

800 seems a little high, and are probly creating enough air current to draw from part throttle and main circuits. Why so high? Do you have a high lift car cam or something?

Auto tranny, so set parking brake, put in gear and set the idle speed you want. The emissions sticker says what rpm. I think its usually around 6-650 RPM. Run each IMS in until lightly seated and back out each independently 1.5 turns. If your lucky they will be approximately equal looking(screw slots vertical or what not). Adjust throttle stop to desired RPM and adjust as your OP says.

Good Luck

 

[Kenny78]

The secondaries are in the back, and shouldnt be opened at this RPM. 1406 Edelbrock right? Thats what I remember from another thread. Are you by chance talking about the choke blade covering up the primaries? The ones in (vehicle)front.

 

[GsxrMike]

Yeah it was the choke blade. So I had a few gear head buddies come over to help me tinker and no matter what we did she wouldn't run right. Decided it wasn't in the carb so we went to the igniton. Late night run to get a new timing light and found that several wires were missing ie the light kept going out while the engine was missing. Dizzy=new, plugs=new, coil=new, cap and rotor=new, plug wires=assembled by a drunker than chit hill billy but new. We pulled a few plugs and found they were barly crimped. We put on a set of old ass wires that had been on a blazer that has been parked in my field for about a year and oh baby did she run. Ran so good I f-ed up and got it stuck in a mud pit in 2wd so bad that I couldn't get it out in 4wd because I wanted to here it run at 5300rpm. I will tune the carb as soon as I get the ol' girl out of the mud. Thanks for the help guys!

EDIT: This trucks main purpose is off road so I would like the idle set a little high to help with it dieing in off camber situations and such.

 

[4X4HIGH]

If you can turn the idle mixture screws all the way in (clockwise) and the engine doesn't die there is a problem with the carb. Also, the vehicle dying while off camber has nothing to do with idle speed adjustment.

 

[GsxrMike]

Also, the vehicle dying while off camber has nothing to do with idle speed adjustment.

Yeah but if I have a mild cam (I don't know what it is) and a poor idle anyways then why not turn it up. By turning up the "air screw" I am opening the primaries just a bit which is in turn allowing my carb to get fuel from a different place than just the idle circut which I think would help. (Key words I THINK) I don't have any better solutions at the moment. Any ideas?

 

[4X4HIGH]

You would have to have the idle way to high before you would be out of the idle circuit and into the venturi circuit. You could have the carb set so your "idle" was 1300rpm and you're still in the idle circuit.