<VV> Rerun: Cold Weather Adjustment for Rochester H Model Carbs

[Mikeamauro at aol.com]

Well, it's finally cold in central Florida (cold here is in the lower 50s).  
This morning the wife made her customary weekly trek to the grocery store. 
Upon  return she asked what I did to the Greenbrier: "it started and ran like a 
brand  new car." Typically, on a morning like this, (lacking the necessary 
finesse  to tame the cold natured beast...speaking of the van, not my wife  :>)  
she would have stalled and restarted the van a half-dozen  times before getting 
out of the driveway. For anyone who missed it, and having a  similar cold 
natured beast (again, speaking of non-turbo Corvairs--with YH  equipped turbos, 
I've found the shop manual adjustments are still spot on)  following is a rerun 
of a previous post:
 
 
After years of putting up with the cold-natured attributes of my Rochester  H 
model equipped vehicles (conditions under 60-degrees being the most  
troublesome), I finally decided to take a closer look at the issue. Looking  at my two 
H model, powerglide equipped vehicles, and numerous spare  carbs on the 
shelf, I found all had the vacuum choke pull off links adjusted to  open the choke 
too far upon start up. Per various bits of literature, the  ideal positioning 
of the pull off is to have the fast idle on the next to  highest step on the 
cam upon starting with a fully activated choke (i.e.: with  the bi-metal choke 
coils calling for full closure of the chokes). Instead,  what I found was the 
vacuum pull offs, at full cold start, were pulling the  chokes open much too 
far; and, as a result, were also stepping the fast  idle cam well down the ramp 
into the barely useful area of the cam (i.e.:  generally to the next to 
lowest step on the cam). The fix: I straightened the  vacuum pull off links until, 
with choke coils calling for full choke, and  vacuum pull offs activated 
(using a Mity vac tool, but one could also push the  pull off in by hand) until the 
fast idle cam was positioned to the next to  highest location. Using wide 
band O2 air fuel instruments, with sheet  metal and thermostat bellows installed, 
excessive choking is NOT evident:  AF readings revert to lean operation 
conditions in about 5-minutes of  driving. To achieve the desired 
adjustments--depending on the individual  carb--straightening of the pull off link was 
required, in some cases, to full  straight, and much straighter than seen in any 
diagrams seen in the manuals  and carb rebuild kit instructions.  
 
Mike  Mauro        

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