Accelerator pump

[dlphil10]

I have been ironing out an off idle stumble. Itll almost cut out when the car is cold. I've lowered the primary throttle angle and it seems to almost go away after the car has warmed up, but its still there at the 10-12inhg range.

I noticed that my accelerator pump stream is quite a bit weaker on the driver side with light throttle changes. I've blown compressed air down that side, but it still seems weak. I have your power piston installed, but it's probably 2 years old and the carb has been dry quite a bit. Is it time to replace?

[Cliff Ruggles]

The accl pump is there to cover up a lean condition with quick throttle movements. 

It's not uncommon for the tiny holes in the airhorn to get plugged up, so first step would be to manually clean them with a small precision drill bit or small piece of spring wire.

Just had a carb in the shop yesterday with poor fuel shot on one side and it required manual cleaning to get the tiny discharge hole opened up. 

If you carb has APT I'd also raise it up slightly to see if this helps?  Also check the power piston hanger arms, they must be level and exactly even.  Most troubled carbs I get in here with complaints like this have bent arms so one side is leaner than the other.......Cliff

[dlphil10]

Thanks Cliff. I'll see of I can free it up. No apt system with this carb (7029262). What is the best way to measure the hanger height and make sure the arms are level?

I had nozzle drop from this weak side of the carb over the summer before adding bypass, lowering throttle angle, and tweaking fuel pressure. Seems like fuel supply to it is adequate but I can check.

[Cliff Ruggles]

First look at the hanger arms and make sure they are level, not bent up or down.

Then pull the rods together under the piston and make sure the tips are exactly even. 

Install the piston into the carb and verify that the meter rods are the correct depth in the jets.

When the piston is all the way up the tips should still be in the actual jet orifice.  All the way down the upper section should just be starting into the jet orifice so the actual full diameter of the metering rod is controlling fuel flow thru the jet.

It's not real fussy but involves exact precision so both sides of the carburetor are providing the same metering area to the engine at any given power piston position.......Cliff