I am having a lean condition when I brake. I say it is lean because if you blip the throttle it recovers and if it dies completely you have to pump the throttle to start it. I have the idle adj screw about 1/2 turn of bottom and the idle mixture screws slighty on the rich side. A richer mixture setting tends to help some but in no way cures it. If you were to kick the car out of gear and roll to a stop with no brakes it idles just fine all the way. there doesn't seem to be a problem when I turn sharply either. I do not have power brakes or anything else that runs off of vaccum. Its a single belt engine with a fan and alternator . Trans is a 4 speed and idle is set about 800. Initial timing is 18. I have checked the fuel levels in all the carbs and they seem to be fine. I am having the problem under normal braking conditions. If I were to panic stop I am sure it would die right away hot or cold. The problem seems to be a lot worse when the engine is cold. Outside temperature doesn't seem to make a difference. Thanks for any tips.

Paul Reber

I'll be interested in hearing solutions to this, too. Mine is on the shelf because of crap like this...

Ya, I would like see what turns up for this also. Good luck.

By the way I've got a six pack too on my 340.

Filter clogged?

Fuel pressure?

Maybe the floats are set right but not enough fuel is making it to the bowls.

here is some advice given to by another moparts member. a little lengthy, but if done in order makes a difference.

have to agree strongly with Mike(HPMike) I've been running six pack inductions for about 30 years now, sm blk, big blk, and even the custom 6 pak cast HEMI intake manifolds that I made for the 71 wingcars,.....I don't have anything but, sixpack cars,,,,,,,,I've rebuilt countless numbers of carbs, along with countless installations and tunings,....when there are troubles, it usally due to someone unfamilar with there tuning or functions, or attempts at trying to improve them,......which usally results in "problem" carbs, starting, stalling, flooding issuse!.....seeing your have "new" carbs/ set-uo,....I'd recommend you use a Carter street pump, don't use rubber hose, it's problems down the road!, use a factory style/ repro steel, or stainless steel fuel line kit,a good quality hi flow fuel filter, AFTER the pump!, not before!, you'll restrict the fuel flow, Factory style linkage, no junk progrssive/ mech linkage!, change out the brass side float screw on the fuel bowls (all 3 bowls) with Holleys clear sight plugs, this way you can see your float level, and no gas spills trying to adjust, their like $4 each,.....when setting the fuel level, I've found that it's best to bring it up to half the height of the clear sight plug, (can't do this with the brass sight screw!, unless you have X-ray vision, hence the need to install the clear plastic sights).....plus "if" you ever have a starting problem, just shaking the car side to side will slosh the fuel in the clear site, and you'll know wether or not you have fuel in the bowl,....after you have basically installed the set-up, and started the car, and set an acceptable idle after warm up, with the engine running, set the floats, start with the center carb, the slotted screw on top of the float adjuster, is just a lock screw, you can remove it for now, the 5/8" nut is the adjuster/needle seat nut, rotating it counter clockwise will raise fuel level in the bowl, clockwise will lower it, make small 1/2 turns let the car run a bit, check the fuel in the clear site window, half the window is ideal height, esp. in the front and rear carbs, when they dump in, you don't wanna lean the engine, which on a sixpack car, might "melt" a piston or two!....really!, been, there, done that!....after you set the fuel level in all 3 carbs, reset the idle on the center carb, by disconnecting the linkage on the end carbs, if your using an idle solenoid, make sure it's energized in the up position contacting the center carbs solenoid idle arm screw, set the desired idle, that keeps your car running, factory specs are a guide line, your cam, vacumm, etc, will affect your desired RPM range, after you establish this idle, this is what your car will run with, now de-energize the solenoid, using the idle srew located on the ceter carbs main throttle shaft, set the idle to a bare minimum running idle, this is were your throttle shaft will close down too when you shut off the car, and the idle solenoid de-energizes, if later you have shut down problems of the car desieling, (sputtering run on after shut down) keep lowering the idle screw on the center carb main shaft, untill this is condition is eliminated, the idle solenoid was added to maintain an idle, and allow the throttle blade to choke off the engine on shutdown if needed, when it de-energized, after your center card idle is set, now comes the fun, start the car, in idle, the front and rear carbs are still disconnected at their main throttle linkage, (important note: make sure no vacumm source is hooked up to the front and rear carbs when main linkage is disconnected, cause any reving you may do, might tip in a end carb! with vacumm!, and if you can't shut it down in time, you might lose an engine!....seen it done!)to properly set the fuel/ air mixture idle screws, start with the center carb, hook up a tach.......warmed up, good idle (low)....turn the fuel/ air mixture screws (2) located on each side of the center carb metering block, do one at a time, run it in slowly, until the engine begins to stumble, slowy back it out watching the tach needle, stop when you've obtained the highest rpm reading,....you can also do this with a vacumm gauge attached to MANIFOLD vacumm, I like to use both at the same time, ...repeat the process for the other side, when done, now re-do-it, again, just to confirm settings, now some of the end carbs, have their fuel idle screws "plugged" with lead, they are located in the base, in the front of the carb base plate, under the bowl, if plugged, dig out lead plug, most people think ones for fuel, ones for air , their not!, you'll adjust these screws just like the center carb, except you can't just use a vacumm/ tach gauge,....look into the top of the front end carb, you see 2 small projections in each bore on each side, just below the neck, these are the air bleeds, block off the outer bleed using your finger over the small tiny hole, with the motor running at idle (low), it should stumble or pick up in idle, when you block off, either outboard bleed, set the front carb first, pick a bore, left or right, with it's coresponding baseplate idle screw, block the bleed off with your finger,(make sure the carbs throttle plate is fully closed) do one side at a time, when you block the bleed, if the idle increases, too much fuel, remove your finger, turn the base screw on the side your blocking the bleed on, in, one turn, block the bleed again, listen for the idle, (you could use a tach gauge at this point), if it stumbles/ decreases, no fuel, back the base screw off a half turn, block the air bleed again see where the "idle" is,......keep adjusting in this fashion until there's no change in idle, no increase/ decrease, you now have the ideal fuel/ air ratio for the vacummm requirement on your motor, complete this for both sides of the front carb, shut off the motor, disconnect this carb remove it, re-install it in the rear,....install the rear carb, now in the front, adjust this carb like you did to the last one, after you hook up everything, now here's when most guys will balk at this move,....they'll insist the air/fuel mixture won't be 100% by moving the tuned front carb to the rear, well if your truly familiar with the sixpack set-up, you know getting to the rear carbs base screws is fustrating to say the least, unless your squeezeing every ounze of effeciency out of the motor, this technique is far better than leaving the factory setting/ lead plugs in, with is usally a lean set-up,,,,,,, after setting this relocated carb up, if you wish you can "play" trying to "tweak" the rear carb, this may include a round of removal the "tweak" the screws to obtain that last ounze of "tuning", I've yet to see a "tool", truly capable of fitting into the installed rear carbs "idle screws"......anybody?,

Well, when your "done" setting the air/ fuel "idle" mixtures on the end carbs, connect the end linkages, to the end carbs, do it with the idle solenoid energized, the rods are threaded were they join together on the center carb, they install on the end carbs with rod clips, there is a F/R or left?right handed clip, energize solenoid, do the front carb first, make sure the linkage is pulled far forward on the center carb secondary rail, thread the rod, in or out, until it fits nicely in the hole, then proceed to the rear, repeat this proceedure, now check the linkage for any binding, you should be able to chrack open (engine off!) the center car, WOT, and manually open both carbs by rotating the front carb throttle arm, close the center carb, check all linkage for binding, readjust if needed, now de-energize the idle solenoid, see if any bind is preventing the center carb from closing on the main throttle shaft idle screw, you may have to comprimise on some idle/ and or end carb linkage adjustments to have an ideal, functioning set-up, but once you take the time to do this, you'll appreciate your efforts!,....as far as altering the end carb secondary springs in the vacumm pods,.....I like a sixpack to come in quick,....you'll have to buy 2 sping kits, replace with the "white" springs if you want a quick responding set-up,....if you what a mid range set-up use the "yellow" springs,.....any thing in the brown or black range is worthless.,,,,,Hell I could write a book here, I probally have, if you have any other questions, PM me.......I wrote this for others, to utilize as well,.......

Wow I'll have to print that... I'll be firing this up soon. I HATE those clear sight plugs though. The strip out after about 3 cycles. I was going to say floats but if you've checked them maybe it's a develery problem. Only problems I've had w/ a carb under stops and hard turns was sloved w/ a float level adjustment. Have you treis rasing them a little more than mid-way?

My current and last carb both caused issues (engine trying to die down) when slowing down to stop quickly. Once I started lowering the float levels, this issue got better each time I lowered the floats.
I started with the manufatured recommendation but then started lowering the floats 1/4 turn at a time until this issue went away. Both carbs ended up with the float levels below the sight glasses (Holley & a QF).

One quick question, Are you using the factory type Idle solenoid or are you setting the idle with the Idle stop screw only?

in my experience with 6-paks, 39yrs, stalling when coming to a stop is usually one of, or maybe both, of two things. the idle mixture screws in the end carbs are set too lean or the float levels are too low. i have two cars with 6-paks and they drive very well. the idle mixture screws in the end carbs are between 3/4-7/8 turns out and the float levels are set to where fuel just slightly trickels out at idle. i use 64 main jets on the "stocker" and 65 main jets on the car with a little cam and headers.

the 64's made it better at part throttle giving me about 13.5:1 afr. i have to fix a few exhaust leaks and recheck it

Great stuff!!

After reading this, I know my mixture screws are out about 2 turns which kind of makes me think the outboard are doing nothing at idle. I will do the clear sightgalsses first to see if the stalling problem goes away or gets better. I think the procedure of setting the mixture on the outboards is well worth doing. I am not running a solenoid and have had no shutdown issues. (yet).

Thanks again

Paul

I had the same problem with brand new Holley carbs on my RoadRunner. Once I adjusted the outboard idle mixture screws it was fixed.

Have you tried disconnectiong the power brake booster to see if the problem goes away???? Be careful as the brakes will require more effort)
If it does go away I would then look at either the booster or the check valve. A leak at either one could create a lean condition when applying the brakes.

If it doesn't you're back to a carb issue

I just had this very problem with my 6 pack set up. I could never seem to get the idle mixture adjusted so that it wouldn't foul the plugs and smell like a gas pump out the tail pipes. I replaced both my booster and check valve and it immediately idled better and cleaner and no more black plugs.

I don't have power brakes or anything else the runs off vaccum BUT after adjusting the outboards by the "cover the bleed" method I could run the mixture screws all the way in on the center carb and it would not die. I turned the outboards in (whew) another 1/4 and the center carbs mixture screws are active again ( about 3/4 turn out) The problem with it dying during braking still persists. As far as the idle goes it seem to want more air than is available at idle(bad fumes)I have read several things about drilling the existing holes in the outboard throttle plates .050 over but may try another method to figure out EXACTLY how much more air it wants. I have tried playing with the float level to cure the dying (one internet site said to lower it until the problem goes away) I don't think they meant as low as I had it (probably 1/2" or so below the sightplug) and it still acts EXACTLY the same. As I am writing this I am wondering if maybe the PVC valve could be doing the brakeing problem??? BTW manifold vaccum is about 12-14 at idle.

if you are idling in gear with the emergency brake on, foot off the gas, and then step on the brake, does it die? put a vacuum gauge on it. what happens to the vacuum when you do this?

if it doesnt die doing that, then you fuel level is wrong. mine was choking out too andit stopped when I lower the level a bit in the rear carb

I don't have power brakes and its a 4 speed. I lowered the fuel level in all carbs 2 flats at a time until the level was about 3/8" to 1/2 " below the sight hole, it still did it. How low did you set yours to make the problem go away ????