Air Bleed Alternatives
Totally agree that not a good idea to just go ch anging stuff. As far as idle being rich. Tailpipe is an eye burner at idle. Plus I have to open throttle plate way too much to get engine to idle and that is at 22 degrees initial on the timing. Also mixture screws are about 3/4 turn out and really not big change with any adjustment. I will install the new carb and run first. No changes. Then check plugs. I have a good article on reading tqve plugs. i will also read the article you provided. Thx
You are correct that the throttle position, mixture screws not responsive and the timing are related.
The Demon guide is a reasonabley good ballpark for initial timing based on displacement and cam duration.
http://www.demoncarbs.com/Tech/DemonSelectionGuide.asp
With the throttle's idle position too open too far, the idle circuit will supply more through the transition slot than the idle port. That's why the mixture screws seem largely ineffective. See if you can reduce the throttle and open up the mixture screws.
Additionally with the throttle too far open at idle, the air coming in the top of the transition slot is less than it should be. One function of the transition slot is that it acts like a variable air bleed. This old Chrysler booklet shows it even though most of the magazine writers miss it.
http://www.imperialclub.org/Repair/Lit/Master/222/Page08.htm
If the cam is too radical, then the throttle can be closed down by drilling a small hole in each of the primary throttle blades. There's other ways to do it as well, but that's the usually old school method. Put the holes near the idle port so the extra air picks up fuel.
Urich and Fisher explain that on Wild Camshafts side bar of their Holley Carburetor books. Highly recommend picking up a used copy of that oldy but goody for explanation of all the systems and basic tuning.
Before drilling, check the PCV. (An inoperative or too large a PCV valve can let in a lot of extra air at idle. Radical cams that produce low manifold vacuum at idle can be an issue with stock PCV valves. )
PS. Before I forget. Once its running half decent, check the fuel level. New style bowls starting point is middle of the window. Old style, fuel level should be just below the hole. But you can adjust a bit up or down for some tuning before you change air bleeds.
Also, on the secondary side, don't mess with the idle air bleeds unless you have to. Not yet anyway. The secondary throttle blade edges are probably very low or below the transition slot. They are not going to effect your normal street driving. They come into play when those vacuum secondaries start to open. This would be high speed Wide Open or nearly wide open throttle - like passing on the highway. Put a little zip tie or paper clip flag on the rod to prove this to yourself.
