<VV> carb balance tube theory

[EUGENE1938@aol.com]

jmac2112@adelphia.net writes:
Can anyone point me to an explanation of how carb balance tubes work?

John,
The tube is not open to the atmosphere anywhere but is terminated at each end 
at the base of each carburetor.  Therefore there is a vacuum in the tube any 
time the engine is running.  The prime function of the balance tube is to 
equalize the vacuum at the base of the carburetors during low RPM (high vacuum) 
operation.  At high RPM (low vacuum) operations the tube does not do much at 
all.  The secondary function is to provide a vacuum source to vent the crankcase 
or PCV system.  This has very little effect on the engine operation at idle 
since there is a restriction in the PCV tube to limit air flow.  In earlies it's 
the PCV valve and in lates it's a small orifice in the PCV tube itself.  So 
now you know.


Ed Corson (CORSA member)
IECC - Riverside, CA