Holly 4150 - Lean Off idle

[Mark H.]

I just rebuilt my 65 SB and it's Holley 4150. Running fine except for just after idle (clutch out @ around 1200 rpm) it goes lean on me - surges on/off hard until I gas it onto the mains (idles and runs on main jets fine). I guess it's the pilot circuit since it behaves very much like a plugged pilot jet on my motorcycle. Carb was cleaned thouroughly after full disassembly. Float level is right; stock jets; choke is working. Thoughts ?

Thanks,
Mark

[Clem Z.]

Re: Holly 4150 - Lean Off idle

I just rebuilt my 65 SB and it's Holley 4150. Running fine except for just after idle (clutch out @ around 1200 rpm) it goes lean on me - surges on/off hard until I gas it onto the mains (idles and runs on main jets fine). I guess it's the pilot circuit since it behaves very much like a plugged pilot jet on my motorcycle. Carb was cleaned thouroughly after full disassembly. Float level is right; stock jets; choke is working. Thoughts ?

Thanks,
Mark

open the idle/air screw another 1/2 turn. make sure the secondary is not open too far causing the primary idle transfer slots not to be open far enought. wrong # power valve.

[Mark H.]

Re: Holly 4150 - Lean Off idle

Clem,

I will try opening up the mixture screws (I had them set to get the max rpm at idle. Thanks

"Wrong power valve " ? The Holley kit did give me a few and, frankly, I don't know if I used the right one or not (I tried - by their looks - to match it up to the one that came out). Would this play into my off-idle problem ? I would think that this would only affect things after the secondaries opened. If it could be the PV, which one should be used.

Thanks,
Mark

[Clem Z.]

Re: Holly 4150 - Lean Off idle

the PV should be a #65