Biochem

On the Q-jet there is a screw on the driver's side for the idle speed, there is a screw on the top that pushes the primary rods down inside the carb, there is a screw on the vacuum canister on the top/passanger side that opens the choke blade, there are two screws in the base at the front that controls the fuel mixture, and then finally there is the screw on the base on the passanger side (under where the choke screw is) that opens the throttle blades inside the carb... I think.

That last screw is the one I am curious about. I noticed that some people drill a small hole in those blades when they have long duration cams. There also is a notch in the wall... what is is and where should the blade be inrelation to that notch. It is about 1-2mm long if I remember right, and the blade can be adjusted to either be above or below the notch and anywhere in between.

Does this adjustment have anything to do with the idle (most certainly does I guess) and is it only during the time when the carb is warming up, or at anytime while the car is on?

Just trying to learn... Thanks!

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock... all the suspension stuff... 9-bolt posi disk is in... K&N filter... 93 octane...

I got the GO... I need the SHOW... Interior is next!

Ed Maher

i'm not sure i understand you but i'll take a shot anyay.
The screw under the choke, facing the front is the fast idle speed adjust..
As for the slot in the wall, i am assuming you mean the slot in the primary bores. That is the idle transition slot (pretty sure thats it's name, but it's definitely it's function.) It should be above the throttle plates. The whole purpose to drilling holes in the throttle plates is to allow a long duration cam to have an acceptable idle w/o having it expose those transition slots (otherwise you would have to open the throttle plates too far.) If they do expose teh transition slots then idle mixture control gets all messed up, and off idle can suffer as well.
Hope that helps...ed

novadude

Ed pretty much said it. The screw you are talking about rides against the steps of the fast idle cam and controls fast idle speed ONLY when the choke is closed. When the choke is open, the drivers side idle screw "overrides" this adjustment.

Biochem

Thanks guys, you nailed it. So Ed, I want to keep the slots above the blades? So basically, the blades are flat/horizontal... or nearly. What is considered a long duration cam? I have a 218/224 @.050...

RB83L69

If you look in there closely, you'll see there is a hole below the slot. Ideally, you would want the throttle blades to be between the hole and the slot at your desired idle speed. That's what people drill the holes for. If the hole gets drilled too large, you can just epoxy the hole back up, and start over with smaller bits.

The other posts are exactly right about the rod. It's primarily there as a choke pull-off, but its secondary purpose (excuse the pun after you finish hurling) is to regulate the rate at which the air valve opens. To tune secondaries, I remove the rod, and tighten the air valve spring until it just barely doesn't stumble when I go from cruise to WOT in 4th gear at about 45 mph; then put the rod back. If you don't have the rod, just give the AV spring about 1/8 turn more tension instead. You should end up most likely with about 5/8 - 3/4 turn of tension on it with a 350, depending on the intake you are running.

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"So many Mustangs, so little time..."