Six Pack Idle Mixture Screws Don't Do Much???

A12 Mopar Discussions

  1. PurpleBeeper

    PurpleBeeper Well-Known Member

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    440-6 w/10.5 comp. & moderate cam & about 10-11" vacuum.

    My six pack has been running pig-rich (can smell the fuel out of the exhaust) & I have been "de-tuning" the carburetors back closer to stock. The only non-stock carb parts I have now are a 3.5 power valve, the power valve holes in the metering block drilled, a Promax back carb baseplate, unplugged the front carb idle mixture screws, 3/32" holes in all the outboard throttle blades (center carb blades no holes). The power valve is brand new and I haven't had a single backfire. I'm running #64 jets & un-modified outer carb metering plates. I can get the engine to idle down to about 700-800 rpm, but my vacuum is around 5" when it's that low.

    I've been trying to set the idle fuel mixture on all 3 carbs & using the "block the outer air bleed hole" method on the outboards. I started with the outboards 1/2 turn out & the center carb 1-1/2 turns out. The only real effect I got was when I closed off the rear carb (zero turns out) which made the idle go up. It "seems" moderately better with the center carb at 1 turn out both sides.

    The problem is I "expected" to need the outboard carbs opened up at least a little bit and when I plug any of the outboard carburetors' outer-most air bleed holes the idle doesn't change. From what I found online that seems like the mixture is correct on the outboards.... but something doesn't seem right.... and I can still smell a little bit of richness in the exhaust and the tailpipes are a little sooty (outboards closed off & center carb 1 turn out each side).

    Any ideas?
     
  2. PurpleBeeper

    PurpleBeeper Well-Known Member

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    Another thing I've noticed is that cruising around town, 25-40mph, I am getting a little over 1mpg. I know I've got 3.91's but OMG! When I had heavily modified carbs and 3.55's I was getting 10 city/12 highway. It's hard to imagine a quart of gasoline being used driving one city block almost at idle......and no, I don't have a fuel leak.
     
  3. D575

    D575 Well-Known Member

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    Holy Crap ! ! Better check your crankcase oil.... Ask me how I know.
    Then check float needles...
     
  4. PurpleBeeper

    PurpleBeeper Well-Known Member

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    You have a good point. I just checked the oil a couple days ago, but I think I need to do it again and smell the oil for gasoline. I also need to be looking down the throats of the carburetors when it's running and look for fuel going in the front/rear carbs. This is ridiculous.

    I was getting a pop-pop in the exhaust when decelerating (vacuum 15"), so I blocked off the vacuum advance and that went away. It got me thinking about my timing again, so I checked it again. At about 700-800rpm idle, I had roughly 12-degrees initial advance and now I turned it back to maybe 5-degrees. I'm getting puffs of lighter colored smoke out of both tailpipes and it reeks of fuel. I backed out the center carb idle mixture screws to 2 turns out and the idle seemed smoother but puffing smoke at idle (still have outboards closed off).....man am I confused.
     
  5. lewtot184

    lewtot184 Well-Known Member

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    if turning the mixture screws in the end carbs all the way in and the engine doesn't die, i'd say you have a float level problem, needle and seat problem or too much fuel pressure. if the venturii boosters are wet at idle then it's one of the three or a combination of the three. you don't state what "moderate cam" is but with anything with 60 degrees of overlap or more 700rpm is too low of an idle speed.
     
  6. Daves69

    Daves69 Well-Known Member

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    ^^^Start there^^^^^

    I actually witnessed a guy pull his aluminum six pack intake a carb assembly off his car and throw it in a scrap barrel over a lousy needle and seat. The Holley needle and seat was new but that didn't make it "good". He never put that six pack back on.
     
  7. PurpleBeeper

    PurpleBeeper Well-Known Member

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    My cam is a Comp Cams Xtreme Energy 21-224-4 274/286 duration, 488/491 lift, 230/236 duration @ .050", 110 lobe separation. I put it in recently replacing an old 292/509 purple shaft hoping to get more vacuum at idle since I was at 2"-4" at idle with the purple cam. Yeah, I'm pretty sure I'll need to set the idle at 900-1000 rpm, but I've had it low trying to get a better read on the affect on idle when I turn the various idle screws. I also have the idle set this low because I'm afraid that even with the 3/32" holes in all the outboard throttle blades I still have the center carb open so much at idle I'm uncovering the idle transfer slots and getting into the main fuel circuit on the middle carb otherwise. Maybe I need holes in the center carb throttle blades too?

    My floats were set too high and I adjusted them down to where they trickle out if you shake the car when the engine is running. This didn't seem to help (maybe a little). I've been toying with the idea of blocking off the PCV nipple at the base of the center carb to get more vacuum and/or put in an oil separator.

    ...anyway, when I pulled off the PCV hose from the PCV valve the idle went WAY up (like 200-300rpm). I checked and the PCV is working just fine. Plug in PCV, idle goes down. Cover PCV hose with my thumb, idle goes way down. Leave the PCV hose open to the air, idle goes way up. To me, this seems like the engine is running super-rich since this massive vacuum leak actually helps the idle. So where is all that extra fuel coming from??? I got a good look inside the front carb and I don't see any fuel flowing at idle...haven't really gotten a look inside the back carb yet.

    My fuel pressure is at 6psi. Should I drop it down to 5psi? How can I be sure my needle/seats are OK? In the past, I only knew they were bad when I got a river of fuel coming out the bowl vent tube on top.
     
  8. lewtot184

    lewtot184 Well-Known Member

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    that cam should easily do 10-12" of vacuum at 800-900rpm, maybe 14". maybe the ignition needs a re-curve.
     
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    • Daves69

      Daves69 Well-Known Member

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      Sounds like the needles and seats are working. Opening the PCV to open air I think will cause the engine to lean out and idle up. Just curious, do you have a breather on the valve cover opposite the PCV or is it closed cap?
      Haven't tried this myself but I might try to isolate center carb from the outboards. Cut off fuel and air to outboards. See what happens with just the center. With intake air and fuel blocked to the outboards I'd expect very little or no loss of fuel in the outboard bowls after idling for a while on just the center.
       
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      • PurpleBeeper

        PurpleBeeper Well-Known Member

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        Well, I'm going to try to look in the rear carb too and also turn the fuel pressure down (regulator on Holley blue & cowl mounted fuel pressure gage). I've thought about isolating the center carb too, but short of making/installing some block-off plates on the intake, the only thing I can think of is to run the fuel line only to the center carb & covering both outboards with thick plastic & rubber bands to seal off the air flow from the top, but I've never seen anybody doing anything like that. Also, I'm not exactly sure what all that would tell me except see if one of the outboards is super messed up or something?

        And Dave... are you sure about the idle going up when it gets leaned out by opening the PCV hose to the air? I mean, I don't know, but my gut instinct is that it would stall or something normally. A small vacuum leak makes the idle go up and down..... a huge leak like that? Please explain what you're thinking on this.

        Based on Lewtot's comment and the fact it reeks of fuel out the exhaust AND basically opening up a hole in the intake (PCV hose open) raises the idle so much and the horrible fuel mileage I'm sort of leaning towards his idea that fuel is getting down the throat of one or more of the carbs "unexpectedly". I'm going to try to re-check the float levels, look down the throat of all the carburetors and turn the fuel pressure down. I don't think 6psi is excessive, but "what if" I have fuel blowing past a borderline needle & seat.

        I have a couple basic carburetor questions... If a carburetor is only on its idle circuit, I won't see any fuel coming out the bottom of the venture boosters, is that right? As long as my vacuum is over 3.5", the power valve won't be open (I have a 3.5 Quick Fuel) and I shouldn't see any fuel coming out of the center boosters at idle AND if I DO see fuel in the center carb and my vacuum is above 3.5 then my power valve is blown, is that right? Lastly, if I have a leaking needle & seat will I see fuel coming out of that carb's boosters or what? How would I know if a needle & seat is just a little stuck open?

        THANKS EVERYONE!

        Today's update....
        1. There is a breather on the valve cover opposite the PCV
        2. I double checked the floats and all are at the lower edge of the sight hole (might set the outboards higher later, but just wanted to make sure the floats weren't too high).
        3. I set the initial timing back to 12-deg advanced & still have vacuum advance blocked off at carb.
        4. Opening any of the outboard idle screws, even 1/2 turn, makes the idle to down, so I left all of them closed.
        5. The center carb - passenger idle screw out 3 turns helped vacuum stay a solid 9.5-10" and the driver's side idle screw does nothing from closed off to 4 turns open, so I left it at 1 turn out.
        6. Turning the idle down to 700 rpm "seems" to temporarily make the fuel smell in the exhaust go away, but the vacuum drops to 7-8" and it eventually starts to reek of fuel again, so I set the idle back around 900-1000 rpm.

        The idle does seem pretty smooth and only a little "thumpy" from the cam, it's just the fuel smell and the horrible mileage & the embarrassing puffs of smoke at stoplights. Man I hate to say it, but I'm half tempted to put the 4 bbl. back on just to see for sure if this is a carburetor issue or an engine issue (engine wasn't run for many years).
         
        Last edited: Jul 5, 2015
      • lewtot184

        lewtot184 Well-Known Member

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        at idle no fuel or wet should be seen above the throttle bores. the only time fuel should be seen above the throttle bores is when the main metering is working, probably above 2000rpm. look for a wet booster(s). those carbs should be fine with a 6.5 power valve and that cam. don't drill any holes in the throttle blades. the factory 6pak idle spec was 900rpm. try another pressure gauge to make sure thats not tricking you. i'm pretty sure your pushing or pulling fuel somewhere. you might want to check gaskets and make sure theres no issue there. the distributor should be recurved to help idle quality when using a non stock cam.
         
      • PurpleBeeper

        PurpleBeeper Well-Known Member

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        Lewtot, you hit some great points.
        1. I checked with a small mirror & all six of the boosters are dry at idle (outboards + center). I could look down in & under them while the engine was running.

        2. Are you sure on the 6.5 power valve? My vacuum can drop to around 2"-4" sometimes, even with the smaller cam. I was worried that if I had a 6.5 power valve & my vacuum dropped below 6.5" (which it does sometimes now & did most of the time with the purple 292/509 cam) that it would go super-pig-rich at idle. I did pull out a 2.5 power valve when I put this 3.5 in and I have tried a 6.5 power valve before that without much difference that I could tell.

        3. Idle rpm - good info. I will shoot for 900-1000 rpm.

        4. I'm reasonably confident in my hood mount fuel pressure gage, but it is pretty old. I turned the fuel pressure regulator down so my gage reads 5 psi and no change.

        5. I've changed the center carb gaskets a few weeks ago, so they're good. That makes me think.... is there some type of gasket issue (maybe '69 vs. '70/'71) where if you screwed up and put the wrong gaskets in you'd get this problem? (way too much fuel at idle). I've screwed up worse than that before...maybe I used the wrong gaskets in the kit?

        6. How can I limit the mechanical advance on my Direct Connection '72-'74 style electronic distributor? Does someone make some kind of advance stop? I would like to run more initial advance, keep the vacuum blocked off and limit my total mechanical advance.
         
      • 69 GTX

        69 GTX FBBO Gold Member FBBO Gold Member

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        I would make sure my timing was correct first. I helped a friend and until the timing was correct, tuning was useless.
         
      • lewtot184

        lewtot184 Well-Known Member

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        i've ran more cam than your running with less compression and a 6.5 worked quit well; but i did have a good ignition curve.
         
      • Meep-Meep

        Meep-Meep дворянин

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        This sounds too familiar! My 6 pack is pig rich too and so far I closed down the outboard mixture screws quite a bit. It helped but I still think it's rich. Need to quantify the mixture but the basic rule of thumb is if it idles when dead cold it's fat. I still need to make more adjustments and do some serious investigating so can't really offer anything specific that hasn't been mentioned. Good thread and I'll add to it if I find something earth shattering.
         
      • 747mopar

        747mopar FBBO Gold Member FBBO Gold Member

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        I'm running the next cam up from that and have no problems pulling 15" of vacuum however mine would run like crap where you have your timing set.
         
      • lewtot184

        lewtot184 Well-Known Member

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        this stuff is very difficult to sort out over the internet. i'm sure if everything was sitting in front of me i could figure it out. there is some piece of information missing or the obvious is being overlooked. i've played with 6-paks for decades and have had rich idle conditions but generally they were very easy to solve with minor adjustments. don't put a lot a faith in new power valves. holley stuff isn't made as good as it used to be. there could be a crack in the carb body or casting flaw,....? i know sometimes people put the carb base gaskets on upside down. i know from experience the manifolds from edelbrock are fairly crummy but they would be more likely to create a lean condition.
         
      • 62MAX

        62MAX Well-Known Member

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        It's long but everyone need to read this and pay attention !!


        This is a guide to tune six packs for street engines.
        Revised 10-2012
        Stroker or non stroker, big block or small block.
        Never the final word, but close enough for now, it gets updated from time to time.




        This is not for the faint of heart. If you wondered why people shy away from six paks just read on.

        When tuned properly Six pak cars turn on! faster & run far better than single 4 barrel cars exc a thermoquad. If you want your six pak car to run like it should do the dance and have the right tools to make it happen. Patience must be used throughout the process. Much of the information here can be used on a 4 barrel as well.

        Some theory of operation:

        Things to Remember:

        Six pak engines run AND idle on all three carbs at all times.

        The outboard are always contributing fuel…always

        Only the center carb has an acceleration pump

        The car must idle and run/drive like a normal car before attempting any secondary action or wide open throttle passes.

        Whacking the throttle in neutral to see if the outboards open is not a legitimate test!!!

        Over jetting will not allow you to get the idle mixture correct as the jet size does contribute to what happens in the idle circuit. Please review the theory of operation in the Mopar Performance Engine book.

        Tools needed: A good vacuum gage, quality tach in the car and dial back timing light/digital tach [snap on timing light with numeric readout].

        A good ignition system.

        MSD, Mallory chrome mopar box, NO orange boxes unless you know for sure it is early 80’s vintage. Anything made after 1988 is questionable.

        Quality distributor cap & rotor
        Firecore spark plug wires
        Spark plugs of the proper heat range. Clean and gapped
        0.040 mopar box
        0.050 msd cd type ignition
        Engine well grounded to the body & battery.
        Vacuum adv distributor with heavy enough springs to hold advance until 1200 rpm.
        The distributor phasing has been checked and corrected as necessary IMPORTANT
        Distributor vacuum port on carb disconnected and plugged at carb


        ATTENTION -195 degree high flow thermostat- ATTENTION
        THIS IS IMPORTANT

        60%water-40% coolant with a bottle of water wetter
        Stewart components has the best thermostats

        Pay attention here: If you run a lower temp thermostat, raw fuel will collect in the intake. That fuel burns off in the cruise mode and the air-fuel mixture goes lean.
        This is transparent unless the a-f ratio is being monitored with a wideband a-f meter
        There will be problems getting it to idle and drivability.

        Make sure the timing is 15 - 18 deg btdc [advance] at idle. THIS IS IMPORTANT
        Set the timing marks at 15 btdc and align the leading edge of the rotor with the LEADING EDGE of the cap contact-this is one reason the phasing was checked.
        Car in neutral-auto or 4 sp, emergency brake set.
        A good quality vacuum gage is required
        Connect vacuum gauge to direct manifold vacuum source.

        The heat crossover should be blocked on big & small blocks
        Note: in temps below 40 degree it will take a good while to get the car warmed up. Block heaters will eliminate the long warm ups.

        Automatic cars: be sure there is enough stall in the torque converter or the car may be a real pig idling in gear and have poor get-up & go.

        Beware of mopar orange ignition control boxes that retard the timing etc. Orange boxes built after 1988 tend to have issues.

        Preparation: on the work bench
        Outboards: Remove the lead plugs
        Set the outboards idle adj screws out 1/8 turn ccw THIS IS IMPORTANT
        Be careful when seating the idle screws to set them before the 1/8 setting. Gently is the word. If you look inside the carb bore you will see the needles poking in ever-so-slightly. They should be equal.

        Install the BLACK springs – Just do it, ignore everything else you have read.
        Install the BLACK springs – Just do it, ignore everything else you have read.
        Yes I repeated that, explained way below

        If you have the jetable metering plates, If so read their instructions and follow them.

        Center carb
        Set the center carb idle adjustment screws at 1.5 turns out [ccw] THIS IS IMPORTANT
        Be sure to adjust the idle screw until the throttle blades are closed and the transfer slot is exposed no larger than a square. [Carb will have to be off the car to see this] You only want about .040" of the transfer slots exposed below the throttle plates. If the idle screw is adjusted too high, you will be into the transition circuit, exposing too much of the vertical rectangular slot. Many times the idle screw is adjusted incorrectly to compensate for other issues. This puts the carb into the transition circuit and at that point you have no mixture control on the center carb.

        If you have new carbs (untouched) they will have 62 jets in the center carb & a 6.5hg power valve. Starting point jetting stock 340 use 62’s, highly modified or stroker use 64’s, big blocks start with 64, stroker 65.

        You must know what power valve is in the center carb. Typically a 6.5

        Reminder 195 degree thermostat required.

        Temporarily change out the brass sight plug on the fuel bowls (all 3) with clear sight plugs, to see the float level without any gas spills. See thru sight plugs deteriorate quickly so use only as a tuning aid. Do not leave them installed on the carbs.

        Do not use an idle solenoid to set idle rpm.
        A properly tuned car will have no “run on” issues

        Factory style linkage, no progressive/ mechanical linkages!
        Installation: use the gaskets made by oh company spec p/n
        Do not over torque bolts.
        Make sure the linkage is set properly. The rods should fall into the hole on the carb lever at the idle setting position.
        Check the linkage for any binding, manually open the center carb to wot and see if the secondaries will rotate open.
        Have an assistant floor the gas pedal and check for wide open throttle

        Fuel pump: Carter street pump only.
        Factory style fuel lines only.
        Use rubber hose only for tuning purposes, typically on the front carb as this is the carb you remove to rejet the ctr. .
        Fuel filter should be in the stock location.

        Ready set go

        Start car & allow engine to reach operating temp. Set idle to 1000 rpm

        Fuel level adjustment THIS IS IMPORTANT, this is best done idling at 900 - 1100 rpm
        The slotted screw on top of the needle n seat is just a lock screw.
        To adj the float level loosen the lock screw to rotate the seat nut.
        Turning the adjuster nut counter clockwise will RAISE fuel level in the bowl,
        Clockwise will LOWER it
        Make only small 1/2 turns and wait 3 or more minutes so the fuel levels off before rechecking level. Patience is a must!!

        FUEL LEVELS
        Center carb the fuel level is at the bottom of the sight plug hole
        Secondaries just starting to come over the bottom of the sight plug hole
        This is critical so get it right.

        Set idle for 900 rpm
        If the car won’t idle:
        Is engine vacuum reading at least 2 hg higher than the power valve rating? If ok proceed, if not correct power valve issue and proceed.
        Note some engines only pull 5 hg of vacuum so use a 2.5 power valve.
        Advance the initial timing a bit to see if it helps idle.
        Be sure operating temp is 195-210
        Be sure there are not light springs in the distributor.

        Now set the initial timing to where it wants to be. Somewhere between 10-20 degrees BTDC. The engine will tell you by increasing vacuum and rpm at this point. In some applications the engine does not care, so set it to 12-14 degrees BTDC.


        Rule of Thumb Chart:
        Cams with 106-degree ctrlines seem to like initial timing set at 16-22 BTDC
        Cams with 108-degree ctrlines seem to like initial timing set at 12-18 BTDC
        Cams with 110-114 degree ctrlines seem to like initial timing set at 8-14 BTDC

        Re-Set the idle rpm for 8-900-See if you have "control" over the idle mixture screws on the ctr carb.

        Using a good vacuum gage adj center carb mixture to highest reading of vacuum.
        This is where the digital [numeric readout] tach is better than the vacuum gage as you can see the instantaneous rpm. If you do not have control over the idle mixture between 1-2 turns out ccw of the mixture screws there are issues that need to be taken care of before proceeding. Over jetting contributes to this problem.

        Typically if you have the center carb idle mixture screws between 1 to 2 turns ccw and the idle mixture/rpm properly set you may not have to adjust the outboard idle mixture any further.

        If you are 2 turns out on the ctr carb idle mixture screws and the idle is still too lean - the outboards need to contribute more fuel to the idle. Open the idle mixture screws on the outboard carbs another 1/8 turn ccw. Now they will be out a total of ¼ of a turn ccw. Now go back and reset the idle mixture and rpm.
        If you need richen the idle mixture-set the idle mix to 1.0 turns out ccw

        Starting with the front carb, adj the mixture screws one at a time 1/8 turn ccw, after turning each screw wait and see what the engine vacuum and rpm do. Obviously if you have a wideband a-f gauge you will see what is happening. It’s a balancing act, just remember about the ctr carb and it’s proper settings. Also remember you have ½ turn ccw left in the ctr carb to richen the overall mixture. The end spark plugs will indicate of the out boards are to lean #s 1&7 / 2&8.

        If the idle is too rich no matter what you do…Most times you are over jetted or you have other issues. Over jetted carbs will have poor idle control. At idle fuel flows from the float chamber thru the main jet then into a the small angular but horizontal passage that leads across to a vertical passage and onto the idle feed restriction where it is mixed with the air coming in from the idle bleed. Remember this. Do not over jet!

        Beware of other issues such as poor intake sealing, carb gaskets backwards, the wrong pcv valve, a vacuum leak from the brake booster or other places, wrong pwr valve, wrong thermostat etc.

        Recheck idle rpm and set to 8-900

        Drive car like a normal person, no wide open throttle. Is the car rich? Jet down 2 steps until you find the min jet size. You will know when you are lean as you will have no power.

        Now reset the initial timing again. Somewhere between 10-20 degrees BTDC. The engine will tell you by increasing vacuum and rpm some point and then falling off. In some applications the engine does not care, so see chart.

        Re-Set the rpm for 900-See if you have "control" over the idle mixture screws. Using a good vacuum gage adj each mixture screw to highest reading of vacuum. If you have a wideband afr meter set to 14.7. If you don’t like this number set it at your number reading. See how close you are between the vac gauge and af meter and digital tach.

        Recheck idle rpm and set to 800-950 depending on engine build, hook up vac adv and make sure car still runs/drives properly.

        How do you know when you are "there”?
        If the car gets up and goes seamlessly you are there
        The engine when hot soaked restarts immediately without touching the throttle
        The car will idle at 700-900 rpm in neutral and the response is crisp.
        There is no smell of raw gas in the exhaust.
        The bottom of the intake is not soaked with fuel. Open a carb and look in
        The spark plugs are clean and white.
        The engine when cold starts easily runs and drives smoothly from the get go.
        When the engine is rev’d and the throttle released it immediately returns to idle.
        The vacuum advance is hooked up and the car drives well.

        OK if you made it this far it’s time for the Secondaries

        The reason you put the black spring is to delay the opening of the secondaries until the engine is ready for it. The engine will run fine on just the center carb till at least 3000 rpm. The air fuel mixture spikes lean when the secondaries open, but at higher rpms this is transparent and has no affect on performance. The opening of the secondaries should be seamless, but very apparent and usually scary to the uninitiated.
        Some cars may enjoy a lighter spring.

        The secondaries rods should be disconnected and removed and the vac signal blocked.

        Please do this safely and with regard for others….
        Go out and drive the car on the center carb and determine what rpm the car starts to fall off in power. Take note.
        The car should have a ton of power just with the center carb.
        Be sure to several wot runs.
        Please do this safely and with regard for others…

        Reconnect carb linkage and vac lines; be sure to set the length of the rods properly.
        Now go for a drive and see what rpm the six pak hits.
        Please do this safely and with regard for others….
        Hold first gear or 2nd gear, run up to 2500 rpm, and floor it. What should happen is the secondaries open without any hesitation and the cars gets up and really goes.

        The long vacuum hoses for the outboard carbs need to be exactly the same length.

        Pulling a vacuum on the hose should make the vacuum pod open the throttle blade and hold a vacuum

        The best way to dial in the secondary air fuel ratio is with a wide band air fuel meter.
        A fine tuned seatofthepantsometer and spark plug reading will work for the more experienced.

        If you made it this far and the car is bogging when the six pak opens you need to go back and recheck starting at the top. Bogs are usually from the secondaries opening too soon!!

        Notes:
        Automatic cars with too tight of a converter will cause significant idle rpm drops when in drive, the car will not run at it’s full potential so be sure to use the correct converter for the application.

        Some cars like staggered jetting.

        Reminder 195 degree thermostat required.

        If car spits fuel out of the vent it means the o ring on the needle seat is bad.

        It’s always easier to remove the front carb for rejetting.
        Tape over intake and make sure there is never any unaccounted for hardware.

        If you are using a wideband O2 meter you will see a lean spike when the secondaries open. It should be small and you should not feel it.

        Do not use Teflon tape or any other sealers on the flare fittings. A drop of light oil on the threads is a good ides



        If the initial timing exceeds 12 degrees BTDC with a MP distributor typically the advance curve will need to be modified so the total timing is not more than 34 degrees BTDC.

        Chart to shorten the slots if you have a non adjustable mopar distributor.
        Distributor degrees X 2 + initial= total
        18 initial plus 14
        32-36 total advance typically, every car is different.
        There should be no advance until 1200 rpm
        Then the advance should increase slowly until it is “all in” at 2400rpm for lighter cars - 2800 rpm - heavier cars

        Dist. degrees / slot size
        6.............. .340
        7............... .355
        8............... .375
        9............... .390
        10.............. .405
        11.5 ........... .420
        12.............. .435
        13.............. .445
        14.............. .460
        15.............. .475
        16.............. .490
        17.............. .505
        18.............. .520


        There are 2 basic plates in the distributor one that has 11deg advance and one that is 17. The slot length on all is .480.

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        • Like Like x 1
        • PurpleBeeper

          PurpleBeeper Well-Known Member

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          Hey 747mopar - What timing are you running? I'm back at 12 degrees initial & vacuum advance blocked off.

          Lewtot184 - Yes, I think I'm missing something. I've started to think maybe I forgot to put a separator plate in one of the end carbs or missed some type of dirt that's blocking a passage, used the wrong gaskets or something like that when I rebuilt the carbs. FYI- before I rebuilt the carbs last time it was POURING fuel into the engine so bad that it got into my oil. It's much better than that now, but still seems rich.

          62Max - I've seen that somewhere before and it's a great write up. I have a few comments/questions though.

          1. My vacuum gage isn't super accurate (not too many lines marking inches of vacuum and I'm doing this myself running from under the hood to looking inside the car back & forth.
          2. I'm running a MSD-6A ignition & my plugs are only stock-gapped at .035"/copper (nitrous)
          3. It sounds super-scary to have the outboards un-hooked (I blew this engine once when the linkage bound up). Do you know of an easy way to "lock" the outboards closed when you unhook the linkage & vacuum hoses? (for safety). What about some zip ties? I've also thought about covering the outboards with plastic bags/rubber bands to block off air flow completely. Good idea? I've read other people making manifold outboard block-off plates to run on the center carb only.
          4. What the heck is all this distributor advance degrees vs. "slot size"? I know nothing about this. I've got a MP electronic distributor and I would like to try a little more initial advance if I can figure out how to limit the mechanical advance.
          5. I've followed these instructions almost to the letter (except the Teflon tape) and I still have the light yellow springs in the outboards.

          I think I might just have to take a look at my plugs. Darn, I wish I had a wide-band O2 sensor so I wouldn't have to use my nose to check fuel mixture.

          THANKS EVERYONE!
           
        • 62MAX

          62MAX Well-Known Member

          My Photo Garage
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          Running just the center carb will not get you anywhere,the end carb idle circuits have to be in the mix to get it right.