<VV> Synchronizing carbs

[Kenneth Schifftner]

Gang:

What Smitty says is correct from my experience using a Dwyer zero center gauge. Indeed the balance is set at idle when the speed screws are in contact with the levers on the carburetors.  Once the linkage is moved to increase the engine speed the idle speed screws do nothing but sit there.

Why the engine is revved further is not to maintain balance it is to make certain that the right carburetor is favored (higher draft than the left) that helps actuate the vacuum advance, etc..  GM only allowed for one complete turn of the link on the left carb so it is easy to be one turn off. I made an adjuster for the left carb and wrote an article about it in the NJACE newsletter.  With that homemade adjuster, the right carb can be favored more accurately.  It seems like at higher revs the balance tube has greater effect.  Really, drivability is what matters. 

Certainly the slop in the linkage is not good. If the effect of sloppy linkage results in the left carb having a higher draft than the right carb at speeds just above idle (I usually use about 1000 rpm) then that slop should be removed regardless of how many extra turns it may take to reconnect the left carb linkage at idle balance.

If the demonstration that was mentioned was the one at Flagstaff, that car did not have the standard linkage.  The car was a last minute substitute.  It had the bolted in swivel type linkage and the adjusting rod was not left/right threaded to act like a turnbuckle.  The swivels had to be removed for each adjustment. The difficulty was with the linkage not with trying to get balanced draft at both idle and higher engine speeds.

I've balanced dozens of carburetors this way with good effect.

Ken Schifftner