7041540 Buick 455 goes lean at WOT

[Rhett]

Just a thought Rhett, have you checked the secondary tubes in the airhorn? Sometimes they're pressed it too far blocking some flow.

I'll check that! But honestly I think theyre where they need to be, this car runs pretty hard.

Kenth - I couldnt edit  my post but had seen where Cliff writes just about the same thing in his book. I've got a set of 67's I can try so thanks for the tip. I think that carb is alreay at .11 bypass. My go-to 540 never had nozzle drip, just wanted huge bypass for idle quality. Even with that, still idles down to 700 rpm, which seems strange to me..I figured it wouldnt idle to below 1200 with .19 

[Rhett]

Here's the config of the spare 540 I put together:

Fuel Inlet   0.152
Float Level   0.250
Accel Discharge   0.033
Idle Tube   0.046
Idle Channel Restriction   0.059
Main Air Bleed (upper)   0.070
Main Air Bleed (lower)   0.070
Idle Air Bleed (air horn)   x
Idle Air Bleed (upper)   0.067
Idle Air Bleed (lower)   0.070
Idle air baseplate   0.110
Mixture Hole   0.090
Primary Jets   0.067
Primary Rods   N/A
Secondary Well restriction   0.040
Secondary POE Restriction   0.060
Secondary Tube Restriction   0.037
Secondary Rods   .044 M DA
Secondary Valve Opening   1.295
Secondary Hanger   F

[Kenth]

Looks like a good start! 

[Rhett]

Nah I tried it last night and it was a plug fouling pig. Looked good on paper anyway. I obviously made a lot of changes at once including going to a M4M float so when I have time I'll go back and make one change at a time and sneak this thing up on final build specs. In the meantime I'll go back to my "go-to" 540

[Kenth]

What is the fuel pressure?
You may have overloaded the inlet valve due to the excessive .152" opening and high adjusted float and got an uncontrolled fuel flow.
Did you check for nozzle drip at idle speed in gear (A/T)?
A .135" inlet seat and 11/32"-13/32" float setting might work better.

[Rhett]

Yeah I checked that, it actually wasnt the idle that was a problem (although It could have used more bypass), it was the cruise/primary power/WOT circuits that just were overwhemed. On both the 540's, the .152/M4M float combo seems to work well at .250, the airhorn gasket just weeps a little.

[Kenth]

Unnecessarily high fuel pressure, an unnecessarily large needle valve and an unnecessarily high adjusted float will invariably work together to cause an excessive fuel level in the float housing resulting in all circuits delivering fuel too early and causing the problems you describe.