AFB carburetor

34ford · September 22, 2007, 06:28:42 PM

Having some issues with the carb so i changed it out with an Carter AFB and it had no book with it in the box so I can't tell which is the full time vacumun port. It is a 9636 for a chrysler product but I'm just using it to see if the problem is the edelbrock 1411 which it was.

With the motor running I put a vacumun gauge on both of the front ports and have no vacumun at idle, only when the rpm's go up so they both must be ported. There is a port by the choke also but it has nothing at idle either.

So my question is do the chrysler products not have or use a full time vacumun port?

Or does anyone know if there is a instruction manual online I can download?

Can't come up with one on a search or at the Federal-Mogul site which is the name on the box as well as Carter High Performance Series

Thanks for the info,

bob

wayne petty · September 22, 2007, 07:39:08 PM

Quote from: "34ford"Having some issues with the carb so i changed it out with an Carter AFB and it had no book with it in the box so I can't tell which is the full time vacumun port. It is a 9636 for a chrysler product but I'm just using it to see if the problem is the edelbrock 1411 which it was.

With the motor running I put a vacumun gauge on both of the front ports and have no vacumun at idle, only when the rpm's go up so they both must be ported. There is a port by the choke also but it has nothing at idle either.

So my question is do the chrysler products not have or use a full time vacumun port?

Or does anyone know if there is a instruction manual online I can download?

bob

http://www.edelbrock.com/automotive_new/mc/carbs_acc/pdf/carb_owners_manual.pdf

the no vacuum at idle, vacuum at speed ports are usually called ported vacuum parts..

there area a few variatons on these as some are timed for emissions like egr..

if you need manifold vacuum those may be found on the back of the carb... differnt carbs have them in differnt places... you can always get it at a vacuum port on the intake manifold...

if you need more ask..

like what exactally was the carb doing...

? flat spot off idle... ??

wayne petty · September 22, 2007, 08:21:29 PM

Crosley.In.AZ · September 22, 2007, 09:22:32 PM

Quote from: "wayne petty"
if you need more ask..

like what exactally was the carb doing...? flat spot off idle... ??

off idle stumble, almost like a mis-fire ... during light throttle. My edelbrock carb has done it since new.... jetted up & down, idle screws adjusted, the dizzy timing adjusted in & out... i gave up.

34ford · September 22, 2007, 10:30:05 PM

Quoteoff idle stumble, almost like a mis-fire ... during light throttle. My edelbrock carb has done it since new.... jetted up & down, idle screws adjusted, the dizzy timing adjusted in & out... i gave up.
________

You hit the nail on the head Tony. Sent a e-mail off to edelbrock to see what their suggestions are. Funny thing is on my last coupe I put the same model carb on and set the idle and ran great with no problems.

bob

Wayne,

thanks for the links. It's like it's missing but not missing. At a high idle(1500-2000 rpm) it's like it keeps a steady rpm but it sounds like it misses then ok then misses again and on and on. If I run it up to 3000-3500 rpm it starts to have a real miss.

wayne petty · September 23, 2007, 01:43:13 AM

Quote from: "34ford"
Quoteoff idle stumble, almost like a mis-fire ... during light throttle. My edelbrock carb has done it since new.... jetted up & down, idle screws adjusted, the dizzy timing adjusted in & out... i gave up.
________

Wayne,

thanks for the links. It's like it's missing but not missing. At a high idle(1500-2000 rpm) it's like it keeps a steady rpm but it sounds like it misses then ok then misses again and on and on. If I run it up to 3000-3500 rpm it starts to have a real miss.

ok 2 differnt answers from wayne...

stumbling off idle is an accelerator pump shot problem... incorrect pump rod ajustment missing pump check balls. too small a shooter nozzle. its going lean during the movment of the accelerator pedal towards the loud position.. with the engine warmed up ... and turned off take a flashlight.. not a match and look down the primarys of the carb...if you bump the throttle lever and you should see a pump shot .. instantly.....not delayed... take the rod link off if it is easy to do and try moving the pump lever.. see where the pump shot starts...put the rod in that hole..or in a hole just after it starts..when reassembled be sure to crank the motor with the throttle partally opened as it will have too much fuel in the intake...be really carefull that you dont pump in too much that you can hydraulic the motor with fuel...

if the shot starts instantly and it is still stumbling you may need to go to a differnt lever hole or a larger shooter size...

see the hi performance carb link above to get the idea... walker products are available through every carb shop nationwide... and a few parts stores as tehy have oxygen sensors and emission controls at great prices... but they only sell wholesale...$40 min order to account holders only... i might be able to buy stuff there as they are local to me.. and the wholesale parts house i worked at has an account there...

here is the accelerator pump nozzles

afb/avs Accelerator Pump Nozzles #1475* edelbrock
Includes .024, .033, .043 nozzles and gaskets.
the owners manual shows they come stock with .028.031.035 so there is some changability..

as for the continious stumbling.. misfiring... look at the ign coil cap and rotor for leaking high voltage...or carbon buildups...

if you have an E core coil like late 80 and early 90s fords and gm's look at the sides.. look for white marks close to the frame of the coil... circular , semi circular.,.. this is high voltages leaking out of the secondary windings instead of going out the top down teh coil wire across the cap / rotor gap down the resistor sparkplug wires and the resistors in the sparkplugs to jump the jap in the hi pressure of your combustion chamber...

since most people dont have an automotive occilliscope or digital storage hand held scope. it gets down to looking at everything... if anybody had a digital volt ohm meter one can measure the spark plug wires.. set the meter on 200K ohm and measure the wires directly... the reading on your meter should be less than the legnth of sparkplug wire.. if the number is higher than the legnth it is going or is bad...

this is written to give the readers of our forum a bit of theory from a mechanic..

not just for one answer.. i teach my tech minded customers this everyday...

Crosley.In.AZ · September 23, 2007, 10:39:59 AM

my problem is not the accelerator squirt / pump. I can ease the throttle open slightly in gear.. brakes on or not... engine goes to a slight stumble / mis-fire act.

What I am saying is I can get the car to stumble as it sits still.... or I can ease the throttle open and the engine stumbles as it moves along slow at parking lot speed

Seems lean , yet I have changed jets & rods. I track what I changed from richer to leaner (both ways) and nothing seems to help. I even filed some small flat spots on the meter rods to richen up the idle transfer and that did not change anything.

Float settings seem to have no effect till you get the float way off ......too low or high.

If I take the car out and run the snot out of it..... it runs WOT like a scalded dog. I can buzz the motor till it runs out of camshaft , shift and buzz it again

The MSD ignition seems to operate correctly. I've thought of changing out the MSD dizzy & box to an OEM dizzy of the HEI design.

Dave · September 23, 2007, 01:18:24 PM

I had one that used to fall on its face when warm but it didnt have to be hot hot . Some self proclaimed carter edlebrock guru told me to change the springs on the metering rods and do this and do that.. Never did get it right and its on the coupe i sold so no worrys for me mate

I have one on the used treasure i put in the roadster frame and I found out it had water in it :?: I pulled it apart and cleaned it and stuff and it starts better than the one on the coupe and idles better so we will see how it runs next summer.. It seems they cant make em the same every time. The one on my 34 was flawless..
Dave

wayne petty · September 23, 2007, 01:28:58 PM

tony.. that does sound lke an ignition problem... what is the timing doing when it stumbles???

does this dizzy have vacuum advance??? if so how much how soon...
(use a vacuum pump and an ajustable timing light, at idle set the ajustable timing light to 0 on the balancer , write down the number of offset on the light. then start pumping the vaccum pump.. when it starts to advance write the gauge reading down. continue till it stops advancing, look at the gauge turn the advance know to bring the mark back to 0 on the balancer and release the vaccum..) write the vacuum reading down and and the offset number.. post the numbers...you can also do the same with the vacuum advance disconected... but with the tach..again idle the motor, 0 the timing with the offset knob, have a friend watch the tach, bring the rpms up , when the timing starts to advance stop and ask the friend what the tach said. bring the rpms up toil it stops advancing 0 the offset knob again.. and shut down.. write the numbers down and post them...

vacuum advance
base timing _________
starts advancing @ _____ vacuum reading_____
stops advancing @ ______ vacuum reading______

centrifical advance
base timing_______________
starts advancing @ _________ tach reading ______
stops advancing @ __________ tach reading_______

can you see a misfire on the coil wire with a timing light...(hook a timing light on the coil wire and look into the light...) try it on a conventional non msd ignition first... the msd ignition system will flash the lamp 3 times pre one of the normal motor but any blackouts would indicate a bad box,pierced insulation on the primary msd wiring..(there is like 350 volts on the primary on msd systems so dont touch or use a volt meter... and msd systems will blow out a scope if you hook to the primary...
some speed shops have a msd tester but i dont know if it is complete or just works or dead.

again.. this in an complete answer for the knowlege of our readers/rodders

i know what you do all day tony.. my feet used to be atf red also... sliding across the shop. no shop should ever be that covered with atf...i don't even know where it came from... it was everywere...getting a 20 minute lecture on how loosing a 3/8-16 nut was cutting into the profit margin was the last straw...

wayne petty · September 23, 2007, 02:10:36 PM

one more thing... off idle stumbles could also be the idle air bleeds incorrect... no amount of jetting will fix that...

my aunt on her 67 caprice 396 had the carb rebuilt.. it would just stumble like crazy off the line... the air bleeds on a Qjet in 67 were pressed into the top cover.. (tiny freeze plugs with holes drilled) later models they were in the main body

on carter four barrels they are installled in the removable primary booster venturi assys...

i don't rembember which ones the idle air bleeds are right now.. someone with a carb in hand will be able to tell.. with the carb apart and the idle mix screw out spray cleaner down the wells under the primary booster. which ever well allows the spray to come out the mixture screw is the idle well. the openings above the long tube in that well are the idle air bleed...inserting small legnth of copper wire into the hole on each side left and right will reduce the air bleed and increase the idle richness . this also effects the idle transition port mixture......and may remove the hesitation off idle.. do not block it totally.. you won't like the results...

while you are spraying make sure the idle transition ports are open... they are the slots just above the tip of the throttle blade when the throttles are closed..

copper wire prevents engine damage if it falls into the intake...

theory of air bleeds...

the speed of the air lifts the fuel out of the bowl and into the wells.. the faster the air the more fuel is pulled over. without any air bleeds a too much fuel will be pulled over. the air bleeds are like a small hole in the side of your drink straw.. the bigger the hole the less drink you get.. this allows for fine tuning.. if anybody wants more theory let me know..

34ford · September 23, 2007, 04:00:11 PM

Quotey problem is not the accelerator squirt / pump. I can ease the throttle open slightly in gear.. brakes on or not... engine goes to a slight stumble / mis-fire act.

What I am saying is I can get the car to stumble as it sits still.... or I can ease the throttle open and the engine stumbles as it moves along slowing at parking lot speed

Seems lean , yet I have changed jets & rods. I track what I changed from ricer to leaner and nothing seems to help. I even filed some small flat spots on the meter rods to richen up the idle transfer and that did not change anything.

Float settings seem to have no effect till you get the float way off too low or high.

If I take the car out and run the snot out of it..... it runs WOT like a scalded dog. I can buzz the motor till it runs out of camshaft , shift and buzz it again

The MSD ignition seems to operate correctly. I've thought of changing out the MSD dizzy & box to an OEM dizzy of the HEI design.

Tony, that a real good description of what mine is doing with the exception of some miss in the higher rpm's. I'd try a different carb before I'd change the dizzy. I have a HEI that came with the motor in mine.

Mikej · September 24, 2007, 06:40:58 PM

Quote from: "Crosley"my problem is not the accelerator squirt / pump. I can ease the throttle open slightly in gear.. brakes on or not... engine goes to a slight stumble / mis-fire act.

What I am saying is I can get the car to stumble as it sits still.... or I can ease the throttle open and the engine stumbles as it moves along slow at parking lot speed

Seems lean , yet I have changed jets & rods. I track what I changed from richer to leaner (both ways) and nothing seems to help. I even filed some small flat spots on the meter rods to richen up the idle transfer and that did not change anything.

Float settings seem to have no effect till you get the float way off ......too low or high.

If I take the car out and run the snot out of it..... it runs WOT like a scalded dog. I can buzz the motor till it runs out of camshaft , shift and buzz it again

The MSD ignition seems to operate correctly. I've thought of changing out the MSD dizzy & box to an OEM dizzy of the HEI design.

It could be that your throttle plates are open to much. Tip in hesitation occurs when you are idling on the wrong circuit. The idle circuit must be adjusted correctly. Throttle plates closed up as much as possible and the adj. made with the idle screws.

Crosley.In.AZ · September 24, 2007, 09:10:02 PM

Quote from: "Mikej"
Quote from: "Crosley"my problem is not the accelerator squirt / pump. I can ease the throttle open slightly in gear.. brakes on or not... engine goes to a slight stumble / mis-fire act.

What I am saying is I can get the car to stumble as it sits still.... or I can ease the throttle open and the engine stumbles as it moves along slow at parking lot speed

Seems lean , yet I have changed jets & rods. I track what I changed from richer to leaner (both ways) and nothing seems to help. I even filed some small flat spots on the meter rods to richen up the idle transfer and that did not change anything.

Float settings seem to have no effect till you get the float way off ......too low or high.

If I take the car out and run the snot out of it..... it runs WOT like a scalded dog. I can buzz the motor till it runs out of camshaft , shift and buzz it again

The MSD ignition seems to operate correctly. I've thought of changing out the MSD dizzy & box to an OEM dizzy of the HEI design.

It could be that your throttle plates are open to much. Tip in hesitation occurs when you are idling on the wrong circuit. The idle circuit must be adjusted correctly. Throttle plates closed up as much as possible and the adj. made with the idle screws.

the motor is on the idle circuits.... I can close the idle screws and the engine dies. Plenty of adjustment on the idle screws ... engine goes rich and lean , etc with screw adjustment.

So. I think the idle circuit is operating and the idle is not very high.

I've done all this stuff twice in the past 4 yrs or so.... car runs the same,

cept when the fuel pump quit. The car was real quiet then... new fuel pump ,& the car runs the same .

wayne petty · September 25, 2007, 10:52:59 AM

ok...

afb/avs owners with off low idle problems. the idle and transition port circuts are described on the bottom of printed page 2 and the top of printed page 3.. (acrobat displayed page 3 and 4) it does not say what to do about it... does anybody have their wide band oxygen sensors hooked up???

perhaps spraying/misting a little carb cleaner into the carb while it is stumbling. if it smooths out the idle transition is lean..

there are two idle air bleeds on each primary venturi booster assy..

it might be a good idea to verify that they are open by removing the assemblys and spraying through each passage with carb cleaner...

C9 · September 26, 2007, 09:45:16 AM

Once't upon a time I had a mildly modified Cleveland 400-M in a 3/4 ton Ford 4x4 which ran a Carter 625.

One day I had the same stumble you're talking about.

PCV valve was NG.

A new one cured the problem.