Trying to adjust a Holley 4300D and can't make sense of the directions

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RC92234

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351C 4V w Motorcraft 4300D carb.  Runs rich and is prone to flooding although when warm starts like a dream.  I'm trying to adjust the carb to run leaner and I'm getting stuck at the first step:  From the 1973 Ford Car Shop Manual, pg 24-21-04: "...set the fuel mixture screws and limiter caps to the full counter-clockwise position".  If I do full counter-clockwise, the screw just comes out.  There's no indent or hesitation, so no way to detect "full counter-clockwise but still screwed in".  What am I missing?

And before I started, the screw on the right side was just barely holding on; when I put the screwdriver blade in the slot it was very jiggly (so I'm surprised it stayed in place at all).  Right side was fine.

Pg 24-21-04.jpg

 

c9zx

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It sounds like the limiter plastic caps have been removed, a good thing. Follow the procedure at the end of the page you attached, "Normal idle fuel Settings" You'll need a vacuum gauge to optimize the mixture screws accurately. You can try going by sound, idle speed, and smell. The flooding when hot is likely caused by fuel percolation, gas being boiled out of the bowl and into the intake, 4300D is famous for this problem. You could try lowering the float level a bit to mitigate the problem. Good luck. Chuck

 
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It sounds like the limiter plastic caps have been removed, a good thing. Follow the procedure at the end of the page you attached, "Normal idle fuel Settings" You'll need a vacuum gauge to optimize the mixture screws accurately. You can try going by sound, idle speed, and smell. The flooding when hot is likely caused by fuel percolation, gas being boiled out of the bowl and into the intake, 4300D is famous for this problem. You could try lowering the float level a bit to mitigate the problem. Good luck. Chuck
Agreed, limiter caps have been removed and you just need to adjust to highest vacuum with a vacuum gauge. Here is a video on how to do it:



 

RC92234

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Thanks for the great info.  Will be picking up a vacuum gauge today, but that explanation of the difference between manifold and ported vacuum is priceless.

And while I waited to hear back from y'all, I did as indicated above:  screw in until lightly seated and then back off 1 1/2 turns and already 100% improvement.

And yeah... mea culpa:  I said "Holley", meant "Motorcraft"

 

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We knew what you meant, many of us are mind readers. :classic_biggrin: Chuck

 

Hemikiller

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Another helpful trick to reduce flooding is to block the auxiliary fuel inlet valve on these carbs. It's a small poppet valve in line before the primary needle and seat, and is one of the dumbest designs I've ever seen. I simply drilled & threaded the seat for a machine screw to block it off on the 4300A in my 71 Country Squire. 

You should also look at the base gaskets for the carb to EGR plate. Many rebuild kits will only supply a thin paper gasket. You need the thick insulating gasket that's about 1/4" thick. Felpro #60301 appears to be the correct part for a 4300D.

 
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