A few posts ago, I talked about a lean condition with my 260 engine with a 1.08 4100. Bill White correctly identified the problem as "rich" not lean. He also advised that the particular carb I have was used on everything including FE motors. This rich condition effected the driveability at 900 to 1100 rpm in the form of a hesitation after the accelerator pump. To compound the issue, the engine also bogged on WOT from idle. THE CURE - After doing some looking, I found a site describing how to tune a Holley idle/transition circuit. They have changeable air bleeds and idle "jets" for their idle/transition circuit. 2100 and 4100 don't have this ability, but because I had a rich condition increasing the air bleed seemed like a good idea. Increasing the air bleed hole by .005" took care of the problem.
Now to the bog. I adjusted the pump arm to hole #1 and used outside hole of the pump lever. This gave me the "smallest" amount of accel. pump action. Still too much. Took out the screw that holds the venturi assy. in place and also allows fuel to enter from the pump to the venturi. This is a hollow screw with two .063" holes. Blocked off the two holes and drilled a smaller one
in their place. NO BOG and a crisp response.
I now have good driveablilty and no WOT bog. Is the carb still too big for my little 260, probably, but if I can still get 18 MPG who cares.
So I quess, you can tune a 2100/4100 to some degree.
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HAVE A NICE DAY!!!!