Air leak thorugh throttle plate gap

[Schurkey]

Problem:  Idle speed high, runs best by far with choke blade partially closed.  Cannot get idle mixture rich enough via idle mixture screws.

Background:  1973 Quadrajet from a Pontiac 455 station wagon.  [will edit later with carb number] Rebuilt by me except for re-bushing the throttle plates (primary AND secondary) which was subcontracted to a local provider.  Rebuild included sizing the fuel and air passages according to your book.  Entire engine was rebuilt and is presently attached to a "test stand" so the engine has about 40 minutes of running time but has never been installed in a vehicle; and cannot be loaded down as there's no transmission attached.

Issue:  I'm pretty sure the lean problem is due to the throttle plates not closing properly.   When closed, I can still see an air gap between the throttle blade and the throttle bore.  I loosened the throttle plates and tried to get a better fit; but nothing seems to make any difference.  The throttle plates just DON'T fit the throttle bores any more; and I think there's a big vacuum leak especially through the secondary throttles.

I'll pull the throttle body later today; it might be that I can get a photograph of light shining through the throttle plate-to-throttle body gap.

What does it take to get the throttle plates (esp. secondary) to seal to the throttle bores?
 
Is it not really an issue and I should be looking for another cause?

Is this common?  Can it be CAUSED by an improper re-bushing of the throttle body?

[omaha]

 I guess the throttle shaft bushing being installed incorrectly could have an impact on the alignment. I like the drill that Cliff sells as it is self piloting for the install of the bushing. (Usually the secondaries do not need bushings). Throttle plates need to be as tight as possible. I could see where the secd. plates not fitting good could cause idling probs.  Are they installed correctly? looking at the baseplate upside down and the primary side facing forward, (away from you) the numbers on the secodary blades should be facing you and on the forward side of secondary the throttle shaft. I unhook the wind up springs when tightening and fitting. holding them in place as best i can befor tightening with the l;ocktight. other than that I cannot think of anything else. sometimes it seems like the blades like to fit in a specific side. I swap 'em around til I get the best fit all around. oh well hope this helps. Hopefully Cliff will chime in with more advice.  BTW. even the best fitting that I have got always seems to show a little bit of light through at some place.

[77cruiser]

The idle air bypass hasn't been enlarged has it?

[Schurkey]

I pulled the carb again; loosened the secondary throttle plate screws (again) and snapped the throttle shut a few times.  Also sanded the throttle body high-spots where the plate did seem to touch.  It may be that the throttle plates are seating better now.

In looking at the carb base gasket, I see that one vacuum passage was probably not sealing properly; and another had a leak from a ported source into manifold vacuum.  Seems like I chose a screwy base gasket that clearly was not intended for this carb.

Putting it all back together tomorrow; hopes are high...