more carb help

[a1elec]

got a 406 with a pro fuel 750. has off idle stumble been moving up in shooter size. im up to # 40. the hesitation is now gone but after idling for 5 minutes the idle starts to drop and it will die. i noticed when this starts fuel seems to be dripping from the shooter or is being pulled from the shooter. fuel pressure is steady at 6lbs. float level at bottom of site plug. any ideas? thanks john

[71 Nova]

Sounds like a leaking float needle, but you said you checked that, both primary and secondary bowls?

Could be a bad power valve leaking thru. I would check that, too. Did you remember to put back the shooter checkvalve? How about the fuel filter? Fuel pressure doesn't always equate to fuel flow. Just some ramblings, hope this helps, I'm sure others have good ideas, too...

[TubbedTruck67]

You might check your accelerator pump to make sure its not to tight.

[a1elec]

yes i checked the adjustment on pump. i will swap out the needle and seat and see what happens. thanks guys john

[drummondracing]

I had one do the same thing and no matter what i tried I wouldnt stop. I was told by an old timer the main body was warped and letting vacuum pull fuel through the squirter????????? I know it sounds crazy but I swapped the main body out and it works perfect now best of luck

[a1elec]

i talked to holley about the shooter leaking fuel. they said when you get to shooters in the 38 to 40 or bigger range vacum will pull fuel from them. they sell shooters to combat this problem. i ordered a couple let you know what happens. john

[dadnova]

Foound this troubleshoot section on carbs.

Fuel comes out of vent tube or runs out A) Lower
float level
B) Decrease fuel pressure
C) Remove, clean/replace needle-&-seat
D) Inspect float to ensure it's moving freely

Backfires or Pops through carburetor A) Open
idle-mixture screws
B) Increase squirter size
C) Increase jet size
D) Raise float level

Backfires or Pops through exhaust A) Lower float
level
B) Decrease fuel pressure
C) Decrease jet size
D) Readjust butterfly position, primary & secondary

Engine won't start A) Prime carburetor with fuel
B) Pump squirters to get fuel flowing
C) Check ignition timing

Fuel leaks from throttle shafts A) Lower float level
B) Decrease fuel pressure
C) Readjust butterfly position, primary & secondary

Is rich at idle A) Increase initial timing
B) Go in on mixture screws
C) Readjust butterfly positions
D) Lower float level
E) Decrease fuel pressure

Stumbles under light acceleration A) Open mixture
screws
B) Readjust butterfly positions
C) Raise float level

Stumbles under hard acceleration A) Readjust
butterfly position
B) Increase squirter size

Won't return to idle A) Increase initial timing
B) Readjust butterflies

Surges at part throttle A) Open idle-mixture screws
B) Open primary butterflies & close secondary
C) Raise float level
D) Increase jet size

Emits black smoke under hard acceleration A) Lower
float level
B) Decrease fuel pressure
C) Decrease jet size