Holley 1920 diaphram return spring
Do you think it is important that both carbs are the same number , or that they are both 1920's ? I picked up a second 3920 a few weeks back from another member , and rebuilt it , but before I asked about the throttle shaft I had already removed it to make changes so it would connect to my linkage , now have a very small leak. That 's why I was looking for another.
First up, Yes it is most desirable to have two (or however many) identical carbs for multiple carburetion. There can be many differences in the same basic model carb that
have a large influence on the way it meters & delivers fuel, idle/main jets to idle/main air bleeds combined with emulsion bleed count/size/height(or lack of), design manifold/
base running temp calibration,high altitude/Cali/fed calibration, variations in power enrichment to main ratios, vacuum only vs vac/manual power enrichment, accel discharge
rate, volume, & timing,...transfer slot/port calibrations........etc...etc..........even two identical carbs have to be timed in sync to function optimally.....My '66 Yamaha YL1 has
a cool little 2 cyl. 2 stroke 100cc twin,...I can feel almost immediately when the cables let the throttle slides get a tiny bit out of sync.,..You can hear and feel it!
So back to Your second 3920, where exactly is the air leak,...around the shaft at the throttle body or...???
