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From: Gary Casey <glcasey@adelphia.net>
Subject: Re:  carbureted lean-of-peak

I used to mess around a lot with carb distribution at GM during the  
carburetor days (when was that?!?).  Anyway, with the intake manifold  
upside-down in the O-320 some of the car tricks might not work - like  
dams on the floor of the manifold.  What would probably work is what  
we called a "dip tube", or in this case a "riser tube".  It would be  
a tube that fits snug in the manifold with a flange at the bottom to  
retain it.  It would rise to some distance above the bottom of the  
individual runners.  From there your imagination can have free reign  
- add notches, slots, bevels etc until the fuel distribution is  
evened out as much as possible.  The sharp edge and the slight  
blockage of the runners will have negligible effect on power since  
the air doesn't follow the sharp corner anyway.  Another sure-fire  
method is to simply space the carburetor further away, increasing the  
time allowed for fuel to mix and vaporize.  As mentioned before,  
adding heat helps.  Another thing often overlooked is to tweak the  
carburetor inlet.  Uniform flow around the periphery is the obvious  
thing to go for, but sometimes a "correct" unbalance will help,  
created by a tab or obstruction in the right place.

Gary Casey