<VV> Single Carburetor

[Sethracer at aol.com]

In a message dated 4/22/2013 8:35:45 P.M. Pacific Daylight Time,  
mmccrae6 at cox.net writes:

Do NOT  use ported vacuum, but draw directly from manifold vacuum.
Mike and I will have to disagree on this one, I guess. I believe you should 
 give the distributor what it expects. The Corvair distributors (Turbo 
models  excluded) were designed to have a stable timing at idle based on the 
initial  setting only, with no vacuum or mechanical advance. Vacuum was only 
applied when  the throttle was opened, mechanical advance at some higher RPM. 
You could do the  mod that Matt suggested, eliminating the Vacuum advance 
completely. If the  initial timing is set with this mod done, you won't have 
the stumble you  describe - if that idle drop is the culprit, and I think it 
is. Running with out  vacuum advance, however, will impact gas mileage at 
part throttle cruise.  Engine vacuum is a reflection of engine load. An engine 
with a light load can  tolerate extra advance and, as GM originally 
intended, more advance is better.  (Okay there is some question on an engine that 
is designed to NEVER ping, More  advance past a certain point gives no HP 
advantage. I assure you the  Corvair engine is not that engine.) Just short of 
pinging is where the Corvair  engine lives a happy life. If you cannot find 
a "ported" vacuum source on the  2GC, you should either look for another 
carb, or eliminate the connection  entirely. GM built several dozen different 
2GC models over 25+ years of  production. Models that fed vacuum at idle to 
the distributor were designed to  work with that style distributor. (not 
ours). If you feed manifold vacuum  to our distributors, opening the throttle - 
which drops the vacuum signal, will  instantly retard the timing - You 
already know the result of that. PS - Which  distributor number are you using on 
the 110 motor? -Seth  Emerson