OK
My Father-In-Law asked me to put a trick kit in a 850 DP Holley, and help him tune it in. I worked on the car before, and knew it was a mosquito killer at idle...Pig Rich. The carb is in great stock shape, which is a very old design with the way of the 2nd linkage was made, also note its a 2 corner idle carb. I ended up using 79 jets in the front, with a 3.5 power valve. and 84's out back with a plug. I opened the Idle air bleeds up .005-.008 over stock. I also added a small piece of Copper wire to the idle feed restrictors. They measure in the .037-.040 range stock. The wire was .012 thick so were looking at .025-.027 now.
I verified timing which was idea, I even advanced it to have 35-38 deg initial timing just to see if it would help clean the idle up.
It did not help at all. It responded well to idle mixture adjustment, it just didn't help. Nothing I did seemed to help the overly rich idle problem, even after I opened the idle air bleeds, and added the .012 wire resitrictor.
The engine is Healthy, and is a .030 stock stroke 440 with KB pistons which compression comes in the 10-10.5:1 range. It has Isky adjustable rockers, and a large solid lift cam. Cam specs are .575 lift, and dur is 272@50 and has a 108LSA and cam installed at 103-104 ICL. Heads are Home ported 452's with large valves, and a M1 4500 flange intake with a 4150 adapter for the 850 Holley.
The car has a 4500 converter, 4.10 sure grip, and Headmen headers.Very Nice car BTW. The car takes fuel great, no stumbling, or dead spots. It smokes like a freight train at idle, to the point of burning your eyes. I tried two diff power valves, and it didn't help. It will idle on its own with out dieing out.
IMO
The carb is too large, the cam is too large. I feel if the engine had another 2 points in compression it would run much better. But it is what it is.
I started to drill some small 1/16" holes in the back two butterflies, but not sure.
I talked him into letting me drag home a 750 DP holley to clean up, and try..

So what am I missing, or any idea's of what to try?? As of right now, I plan to go through the 750 and give it a whirl.

if you were thinking about drilling holes in the throttle blades than that has me thinking they are open to far exposing the transfer slots and since you never mentioned that. i would start there

Where are the floats at? Does it clean up if you screw in the mixture screws? Have you looked right in the carb to see if its pulling out of the mains? Kinda sounds like the butterfly are open too much..

In addition to the butterfly's being open too far,, what vacuume reading and what rated powervalve and also too high a fuel level.

Fuel level is below the sight glass, Its not pulling fuel from the boosters. I flopped it over and they was about .020 or so transfer slot exposed. It was idling somewhat on the idle circuit, I could kill the engine with a few turns of the idle mixture screws.

I forgot my vacuum gauge, but a 3.5 " of HG PV should have it covered.

Bob correct me if I am wrong, but I thought you added the wires to the idle air circuit if it was too lean at idle. My 1050 was running super rich at idle and I installed larger air bleed jets in each corner. Went too big and it would not stay at idle. Kept leaning out. i used the wires to get it back to a correct idle mixture. What does it do if you remove the wire from the idle air jets?

Looks like I may have opened up the wrong air bleed, which was opened .005 or so. I opened up the inner bleed (smallest of the two) thinking it was the idle air bleed. Looks like from this picture the larger of the two is the idle circuit air bleed.
Can anyone confirm? The carb in question doesnt have screw in bleeds BTW
How much should I open it up if all else fails? .010 be too much?

Yup opening up the inner helps to increase fuel at idle it is an idle circuit restrictor. the air bleeds you open up for leaner idle and install smaller for richer idle!

To lean the idle mixture down you need to restrict teh amount of fuel getting into the idle circiut, one way is to turn the idle mixture screws in until it want to die and then back them out 1/8 to mayb 1/2 turn more. The other way is to enlarge the idle air bleeds in the top of the carb, the outer ones. I have done both with sucess but you have to creep up on it a little at a time. Start with turning the mixture screws in to 1/2 turn out from bottomed out and then see how you like that, if it drives nice, no stumble from off idle, then try turning the screws in 1/8 turn more. Keep playing with it until you like it Make double sure that the idle vacume reading in gear is more than the 3.5 power valve you have in it, also check the power valve to make sure it is working correctly and the gasket is not oblonged on the metering block or hanging over the step on the power valve BTW, by opening up the high speed bleeds you may have also help that old carb flatten out the fuel curve at high rpms(above 5000RPMs)

first thing I would do is convert it to 4 corner idle adjustment. and open the rear blades a little.

I think you're on the right track now that you figured out you opened up the wrong air bleed. Don't you hate it when that happens?

Wire in the IFR is a good place to start, but it's hard to be precise, because if the wire isn't inserted perpenducular, it's "footprint" becomes larger than you calculated and can be confusing. You've gone this far - I'd recommend drilling and tapping the IFR for 6-32 and drilling 6-32 set screws to the desired size and screwing 'em in. Then you know what you've got.

What size IAB is in the primary now? Eventually, you'll reach the point of no return where still-laregr IABs won't make any difference, and then it's time to drop the IFR down a few thou and start over. I never go larger than .080" on the IAB, although I've never experimented to find out exactly where the max is.

I usually start with something like .036 IFR and .076" IAB ona an engine such as the one you're working with and begin tuning from there. Your wire makes the IFR the equivalent of a size that I would guess to be way too small. Sounds like something else is going on, unless the IAB is tiny.

Don't forget, it could be the secondarys idling too rich. As a previous poster said, you can convert it to 4-corner idle. An easier solution is to increase the IAB size on teh secondary side and see if that'll get you where you need to be.

How about an internal leak? Did you file the main body gasket surface until it was flat?

Jim

Something looks strange about this metering block

The idle passage appears to be soldered closed?

Also the wire is located in the well. This will limit the fuel in the well, however normally ifr is jetted in the upper portion of the "dog leg"
limiting both air and fuel, as opposed to just fuel the way it is shown now.

You might try the wire up higher in the block to limit the ifr?

Is there a idle feed passage in the carb throttle base?

It appears that this carb idles through the transfer slot.

Are you sure the power valve is working? I bought a 750 one time that had the wrong gasket between the baseplate and main body. The gasket didnt have the hole that feeds vacumn to the pv.

They measure in the .037-.040 range stock. The wire was .012 thick so were looking at .025-.027 now.

Doesn't address your problem, but the actual math is:
New area = (hole diameter^2 - wire diameter^2)^.5
If the hole is .040" and the wire is .012", the result isn't the same as the hole size minus the wire size (.040 - .012 = .028), but (.040^2 - .012^2)^.5 = .038, only 9% smaller.

If you are using the symbol^ as divided by, then I think you slipped a little on the calculation.
.040/2=.020,.012/2=.006 then .020-.006/0.5=.028 and not .038
But, I certainly coud be mistaken