Carb Sync procedures

[mark_gober]

Hey everyone,

Thanks for everyone's advice on my battery/carbs.  I'm now coming to the forum, begging for a hand.

I've had these carbs off three times for what was supposed to be a rebuild.  Each time, I've had to pull them back off for several problems or oversights during my previous attempts.  I'm convinced that the carbs are set up correctly now (float heights are identical, pilot screws are all exactly the same, butterfly valves were visually identical).  I installed the carbs and upon initial startup, the vacuum gauges were all EXTREMELY close.  There was no more than .5" mercury difference. 

Here's where everything takes a turn for the worse.  In trying to dial everything in the next day, I connected my vacuum gauges and suddenly my #4 gauge was showing 10" of vacuum with the others approximately the same (about 4").  I started fiddling with the adjustments trying to bring it into spec.  As many of you probably know, fiddling with one adjustment throws the others off.  Then I shut the engine off and the #4 gauge didn't zero.  Turns out I either broke the gauge or it died.  Either way, I'd messed all my values up because of a stupid broken gauge and now I feel like my only option is to remove the carbs and re-bench sync them. 

Does anyone have a tried and true method for synching these carbs?  I'm referring to bench synching them and then in what sequence they need to be synched.  I'm really hoping that this is the final time to remove these carbs. 

Mark

[John Luttrell]

You are on the right track; everything should be adjusted to match the #1 carb; that's the carb that the throttle cables run to it.  So with the throttle closed, find a drill bit that correctly matches the amount of butterfly opening on the #1 carb.  Then adjust the rest of the carbs using the drill bit as a feeler gauge.  This method can get them so close, they may not need any adjustments with a gauge set afterward.

[Greg Cothern]

They range they give for acceptable difference from one another is broad.  I have never found it necissary much if a bench sync is good.