<VV> RE: Primary Secondaries

grant young gyoungwolf at earthlink.net
Fri Oct 26 20:50:38 EDT 2007


<I have a 1966 140 Corsa that has primary carbs all the way around (all 4). 
What do I need to do in the way of carb mods to use primaries in the 
secondary positions.>
This obviously won't work, or GM would have made them that way...

Actually, you should remove the choke shaft and plug the choke shaft holes
(to keep out dirt). You might also consider plugging one of the pump
squirter holes if you find you get a bog or stumble when they are
activated. Other than that, just have some fun getting all four synced for
a smooth idle. I'm not sure why people (other than having a secondary go
bad) do this as a secondary flows slightly better than a primary, so you
are giving up a bit of top end and well as adding another variable to the
rough idle problems we sometimes have.
There is always some debate as to whether secondary carbs had or need
accelerator pump cups. I have recently had a dozen or so NOS secondary
carbs from all years and they all had pump cups installed except for a pair
designated for an A.I.R. engine. These carbs also did not have the passage
from the pump well to the outlet area drilled. It is easy to tell which
carbs don't have the passage, as the rivet at the bottom of the pump well
is missing.
Hope this helps,
The Carbmeister




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