6 BBL stumble...

[P Dubya]

I am starting to have some stumble on acceleration. Previously ran and accelerated great/no stumble. Sounds like a popping noise from carbs. If I stand on it hard enough and keep after it the stumble goes away and there's all kinds of power to be had.... Am I correct to think that this is most likely a problem with just the center carb? Any pointers on what I can check? Plugs, wires, etc replaced last summer. 440/6 BBL

 

[P Dubya]

Very well could be accelerator pump as it runs like a raped ape once the other carbs come into play.
Timing is good
Idle speed is good and smooth, all cylinders firing.

 

[Budnicks]

Squiter size ?
could be a slightly clogged accel./pump nozzle
all the additives & ethanol/alcohol **** they put in gas now,
usually leave behind a;
lil' white or pinkish crystals that clog the lil' tiny orifices
mostly from the alcohol content
take the squirter nozzle off, clean it out really well,
Aerosol Berrymans should do it
then spray some (any decent carb cleaner) carb-cleaner
thru down into the carb side too, flush it out good

if the car has sat a bunch it'll get 'that **** in the bowls too'
same stuff;
'lil' white or pink-ish crystals, clog shit'

stumbling is usually the squirter size/discharge is too small
not enough fuel
(an off chance if it's an older set up, it could be a worn plastic cam for the accel./pump too)
or a restriction, in tip-over/tip-in (?) when you 1st hit the throttle

maybe also check the diaphragm in the accel./pump too
or the adjustments on in the linkage on the accel./pump cam lever too lose
possibly (?)
or bottoming the lever out too tight (?)

partially clogged main or secondary fuel filter too

do the easiest stuff 1st

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In my experiences
a Coil 'taken a dump/going out-away', can have a stumble too,
it sort of acts like a carb issue at times, been there too

guess that's a few things to check

good luck

 

[lewtot184]

a cold intake, especially this time of year, can create a stumble. i preferred a .025" squirter with tubes and a white 218 pump cam when i was running 6paks. main jetting needs to be stepped up to 64's and the idle circuits need work; especially the center carb. i wouldn't run a completely blocked heat crossover. fuel has to atomize and some heat can be beneficial in colder climates. i preferred either yellow or purple springs in the end carbs. purple is a very good general purpose spring for a taller geared heavy automatic trans b-body.

 

[P Dubya]

a cold intake, especially this time of year, can create a stumble. i preferred a .025" squirter with tubes and a white 218 pump cam when i was running 6paks. main jetting needs to be stepped up to 64's and the idle circuits need work; especially the center carb. i wouldn't run a completely blocked heat crossover. fuel has to atomize and some heat can be beneficial in colder climates. i preferred either yellow or purple springs in the end carbs. purple is a very good general purpose spring for a taller geared heavy automatic trans b-body.

This stumble happens all the time. Hot or cold.

 

[Geoff 2]

I do not see how it could need jet/squirter changes if it previously ran great with no stumble....

 

[P Dubya]

Some update... Have had the carburetors professionally rebuilt. Installed today and it seems to run good at idle. I have not driven it yet but I can hear a miss on the passenger side. I have had other people tell me all kinds of bad things could be happening but I would like to rule out the possibility of something as simple as a bad plug or wire. I plan to look under the cap to see if I can see any issue there but since the miss is coming from the passenger side I think I can rule out the possibility of the coil or other ignition parts leaving the chat....They (plugs/wires) are relatively new, maybe a year. Doesn't mean I couldn't have a bad one. I am open to opinions on best plugs to use. I honestly don't remember what brand is installed at this time. Also what ohm reading should I be looking for on a bad plug wire? Thanks!

 

[Mick56]

You could check all the plugs wires and get an idea of the resistance. If one wire is waaay different than the others, it could be bad. If they're all about the same, look for something else.

 

[P Dubya]

I did find this condenser wire insulation to be old/cracked. All the plug wires on passenger side in my opinion seem to ohm out about right. About 5K ohms on shortest wire. 8K on next longest and 10-11K for next two wires.

 

[Geoff 2]

The condenser could be faulty internally. It is a noise suppression capacitor; leave it disconnected & see if the problem is fixed.