Ohhh I’m as bullheaded as you can get on some subjects but then again some guys can tune a carb, some guys send them to the experts, and some guys switch to fuel injection and have issues with that and need the experts to help get it straightened out. Lol

Oh, look... a carb with an adjustable idle air bleed.

Adjustable air bleeds or replaceable?

There is an idle air bypass screw that is adjusted with a screwdriver inserted into the air cleaner stud hole. It allows you to vary how much additional bypass air is let in through the four holes below where the stud screws in while allowing the throttle plate opening to remain in the proper location to keep the idle circuit active.

Thanks for the offer Brad I may take you up on it if I can't figure it out. I actually was in NoVa today for a meeting and I drove by Sterling. I take RT15 through to avoid the beltway. I live in western Howard County about 60 miles.
Out of the box the carb was lean at idle and would die instantly when put in gear and I had the idle up to 1400-1500 to keep it running. I do have a wideband meter but it is an old LM-1 and it was reading crazy lambda numbers. Not sure if the o2 is bad or open headers. Currently it idles 1300 in neutral and 900-1000 in gear and is rich at idle.
I did stop on the way home and picked a drill bit to open up IABs that was suggested. If I have time tomorrow I will give that a try but work has been busy. Wanted to go to Mason Dixon on Saturday or Capital on Sunday. Want try the new engine before winter.

Seems like drilling throttle blades is like asking about pinion angle.

Doesn't sound like a happy carburetor... at all.

Pinion angle: 3* for CalTracs; 5* for Super Stock springs.

You might have some other problem going on so don't assume that drilling the throttle blades will solve it (or do anything at all).

At 378 cubic inches you shouldn't need to drill the throttle blades. That isn't a really big engine so it shouldn't need a ton of air at idle. If you have both sides open 0.020 on the transfer slot you should be okay. If idle mixture screws are all out 1.5 turns then it should run. If it was me I'd borrow another carb first just to see what happens. An engine like that should be pretty happy with a box stock 850 or anything close to that. The carb you have should work just fine too. You might want to take your carb all apart and double check everything. A metering plate gasket on backwards can really mess you up as can a missing jet somewhere or something like that.

How are you determining if it's lean or rich by smell or do you have a wide-band.....

By smell and looking at the plugs. I do have an older LM1 but not working right.

Call me if u'd like and I can walk ya through some stuff........

The sensor needs to be at least 18" or more upstream from the end of the exhaust or you get reversion showing dead lean, especially at idle. Also no leaky header tubes or gaskets allowed.

If you have the sensor mounted in the collector on an open header, put a collector extension on it. An LM1 is a good unit.

Kevin

Thank you. I will when I get a chance.Didn't get a chance to work on it today because work got in the way. Also I want to get a clean set a plugs in it first.

Yeah I kind of figured the open headers might be causing it. The sensor is no where close to 18" upstream.

That's a very nice feature about some newer carbs. And I agree without an air bypass there pretty much is not another way to let more air into the eng to raise idle speed and keep the throttle blades in the proper position with the transfer slots. Holley even says in there books to drill the throttle plates for just that on their carbs with no idle air bypass. Its a simple way to let more air to the eng and not effect anything else other then raise idle speed. You cant do it through the idle air bleeds as that will effect the idle mixture. Its just a way to let extra air into the eng so you can raise the idle and not move the throttle plates. Course you know some Carter carbs like older AFB's had that big idle air speed screw in them in the front of the carb in between the idle mixture screws to raise the idle speed. Ron

As far as to not ever drilling plates, not true, holley drilled and reamed .078-.080 holes on all 6 plates on factory 6bbl 440 setups, 383 holley carbs had holes. the air has to come from somewhere for it to idle with the plates closed. I doubt a 400 inch engine could idle on 4 idle circuits with all 4 blades closed, most have the rear blades cracked by the set screw for idle air. If you have an adjustable air bypass, different story.

I have only drilled holes in 2-bbl dirt track Holley's so far the rest all work out by getting the proper ifr's, idle bleeds and the right mixture screw settings. Long t-slots become a problem on some old Dommy's then I drill the main body next to the stud hole, drill n tap for 10-32 set screws and get my air there......

If at all possible I would try the air-bleed adjustment / test first.

I spent a significant amount of time getting my Carter TQ 9800 to idle nicely. Initially I went down the path of drilling the plates but that was a stop-gap measure. It only gave a very "static" setup, meaning as soon as something else changed the previous combination wasn't spot-on anymore.

Eventually I went studying the TQ circuits enough to understand how to re-work the TQ passages (by installing brass plugs that are drilled to a particular size) that actually gave me a poor-man's adjustable air-bleed configuration. This now means that as my jetting changes I simply go up or down the air-bleed size to make sure the idle ports still have enough fuel flowing to feed the motor. Co-incidentally (as expected) this approach also cleared up the part-throttle situation. The idle-to-primary transfer is much nicer now.

Now that I'm changing my motor I should be able to simply adjust the air-bleed sizes to get the TQ to flow the right amount of idle fuel.

BTW: Small block 360 motor, HE3844 hydrualic flat tappet cam (238/244, 108LSA), 21 initial advance, 35 total, 800 RPM idle speed, drops to 700-750 when in gear.