TUNING A SIX PACK

A12 Mopar Discussions

  1. mac

    mac Well-Known Member

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    the carbs i had were pretty rough and just about anything would be an improvement. also, like i mentioned before, i did not have a good experience with the Promax replacement.
     
  2. 440beep

    440beep FBBO Gold Member FBBO Gold Member

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    do you by chance have a photo of these small screws? I'm trying to visualize................

     
  3. MAPS

    MAPS Active Member

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    So you are saying i am better of putting back the 6.5 valve ?
    Thank you.
    Zoi
     
  4. 66Satellite47

    66Satellite47 FBBO Gold Member FBBO Gold Member

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    No my 6 Pak's are long gone. If you look under the base plate on the end carbs you can see the screw that sets the throttle blade position. You need to have the end carbs off to see it.
     
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    • 66Satellite47

      66Satellite47 FBBO Gold Member FBBO Gold Member

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      As you look through this thread you can see that 6 Pak's need a lot of tuning attention to run real good. The power valve should not have a real big factor at idle. Try a few. But start with the basics. Float level, idle mixture screws, main jet size. On most stock combinations the end carbs are lean, maybe not yours. Many 6 Pak's got modified back in the day, look to see if yours is one.
       
    • MAPS

      MAPS Active Member

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      Thanks I have done everthing and twice.
      My last bet is sending them out to some guy everyone swears by and see what happens there and if that is not succesful ...4 "pack"
      here I come...lol
       
    • RJRENTON

      RJRENTON FBBO Gold Member FBBO Gold Member

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      If you do not get your problem fixed and proceed with your "4 pack conversion", I'll give your old carbs s good home.....
      BOB RENTON
       
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      • 66Satellite47

        66Satellite47 FBBO Gold Member FBBO Gold Member

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        Which intake are you using, and which carbs? The '69, 70 & 71 carbs seemed to be very different in what they wanted.
        A 4BBL will likely take some work too. I spent over two months and at least 100 runs to get my 850DP and TM7 intake dialed in. No instrumentation, computers and O2 sensors back then.
         
      • BrianInTexas

        BrianInTexas Member

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        Is there anyone in south/central Texas (I’m about 65 miles west of Houston) with six pack experience that can help me dial in my car? I can adjust fuel levels in the bowls and adjust idle mixture, but I have only a little experience (rebuilt a 4 bbl and changed power valves) beyond that with fine-tuning carburetors, and no experience with six packs. My car was running well and then spark plugs fouled…I believe the front or rear carb float/needle/seat stuck open and started flooding the engine. I changed the spark plugs, checked the bowls/floats and plan to get some clear bowl plugs to set the fuel level as described in this post. However, for me to go beyond that, I’m more likely to make things worse, or as Clint Eastwood said, “man has got to know his limitations.” I’m also open to trailering my car to someone that can help. Of course, I expect to pay for this and hopefully make some new friends along the way. Thanks, and I’ll post updates after I experiment with getting the fuel level correct in the bowls. Brian
         
      • 66Satellite47

        66Satellite47 FBBO Gold Member FBBO Gold Member

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        You do need to get the float levels correct. If needed replace the needle/seats. Stock jetting is probably pretty close. I found that on the end carbs, taking the end carb idle mixture screw plugs out and richening them slightly 1/8 or 1/4 turn made a big difference. Also on the end carbs the idle throttle position has an adjustment screw below the baseplate. I found that that helped, but I had a pretty big cam.
         
      • BrianInTexas

        BrianInTexas Member

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        Thanks for the suggestions…I’m going to start with the floats and go from there.
         
      • AAR4Fun

        AAR4Fun New Member

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        I know this post is sometime back in the thread, but need to know. Were you experiencing any stumble or falter with the lower PV while the pedal is in motion and before secondaries come on? My AFR leans from mid 14's to 16's before more fuel is introduced and it comes back down. This is with only the center carb functional.
         
        Last edited: Nov 15, 2021
      • Frustration

        Frustration Well-Known Member

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        Sorry for the delay getting back to this bogging off the line, and lean condition in the 4000 RPM range. I noticed a fuel leak on my intake manifold. Not a ton, but enough to smell and a small puddle would form on the driver's side. I found out that the accelerator pump had warped due to someone (probably me) overtightening it. I put a straight edge on it, and it was considerably bowed. I used a fine file and brought it back to square. It solved the leak as well as the bog down low. It was actually pumping gas out between the accelerator pump and the carb base. It was enough to see when I took the air cleaner off. May be worth checking if you have an old set of carbs.
         
      • 68 HEMI GTS

        68 HEMI GTS Well-Known Member

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        I could see it on the A/F gauge, it felt slightly smoother with the higher number PV as well when you accelerate from a roll. Keep in mind if your vacuum outboards start to open you will see a lean spike untill the boosters turn on. No way around it.
         
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        • Frustration

          Frustration Well-Known Member

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          Here's a little update on a change I made yesterday. I was able to borrow back my old Weiand six pack, tunnel ram from a close friend. This intake has all the Mopar Engine Book modifications to the inside, including dams and grinding, as well as a jet change to my stock carbs per the book. When I started the car, it seemed to have a vacuum leak. I took the intake back off and re-sealed it with new gaskets. Upon startup, it did the same thing. I started to play with the air/fuel mix and that cleaned it right up. It wanted at least two turns on the center and 1 1/2 on the outboards. At that point, it ran near perfectly. I took it for a ride and was pleasantly surprised with the road manners, though it did change the note of the engine in a positive way. Once warmed up, I matted the throttle at around 45 MPH while in high gear. The car fell over for a second or two, then took off like a banshee! Thinking further, I never changed from the soft, yellow springs in my outboard carbs. I'm guessing they opened the secondary carbs too soon, and there was not enough fuel to support all the air. I also have the same squirter in the center carb. Today I plan to change springs and squirter before our cruise. On a side note, I took the car to my buddy's house to show off the cool intake. A few of my friends were standing around the engine bay, admiring it and asked to start it up. I told another buddy to reach in and hit the key. With no throttle action at all, it fired up and idled like a stocker. To say I'm pleased would be a gross understatement! One final note...further back in this thread, a question was asked whether this intake setup would fit under the stock, lift-off hood. It does, but not without modification to the air cleaner base. I ran the car without an air cleaner as I don't want to cut my original base. I run a reproduction hood that is very close to the original style, including the part under the scoop where the air cleaner seals to the hood. That is where the air cleaner hits. I used to run a cheap aftermarket hood that had a much larger opening under the scoop. That hood cleared the air cleaner in stock condition. (this is not the A12-style base, but the other, oval style. The A12 base will not work) I hope this bit of info helps others as this intake is one of the coolest I've ever laid eyes on. Good luck my friends!
           
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          • 68 HEMI GTS

            68 HEMI GTS Well-Known Member

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            sounds like it works pretty good. I’d consider modifying the stock intake If you go back. I worked the dividers down a bit on mine. I picked this mod up from a guy with a really good running six pack stroker. It seemed to strigten up some of the low speed manors and it flat screams at WOT. Then I seen a very similar mod on a dyno test on YouTube the other day.
            8716D307-C9A9-4C24-A1B7-45D60B171B7F.jpeg B6836604-18E4-4E63-BBCA-1821BB8F9EE7.jpeg


             
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            • Frustration

              Frustration Well-Known Member

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              That's really cool. Would love to know how much difference the mods to the intake made. I'm sticking with the Weiand for a while anyway. I may do the stocker mods though, while it's off the car. Thank you for posting.
               
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              • 68 HEMI GTS

                68 HEMI GTS Well-Known Member

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                I don’t have any track data with the modified six pack or the mechanical carbs for that matter. It feels quicker than when it made the 10.90 passes. Although I’m putting a 4 speed in the car so I’ll never really get a true good test. The guy who I stole the intake mods from had a 12:1 TF240 headed 512 in a full steel 70 bee running 10.40’s. That helped make up my mind to try it. He was kind enough to share some really good pics of the mods. His manifold was ported by MCH. Same car but slower dial as it had iron heads in the pic. Real V code as well!

                C0D919F8-3DBC-4793-B66E-3B8A5EB5AF4F.jpeg
                 
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                • rumblefish360

                  rumblefish360 Well-Known Member

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                  Very nice car.
                   
                • biomedtechguy

                  biomedtechguy Accelerati Rapidus Maximus FBBO Gold Member

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                  A few quick notes on a great thread.
                  DON'T LEAVE CLEAR PLASTIC fuel bowl site plugs in any longer than needed to adjust the float level! They rapidly get soft and melt. I know from personal experience.
                  I have a beautiful example of the Weiand P3690982 6bbl intake, after researching it more than any sane person should. The only mods on mine are the sharp 90° angles where the plenum floor meets the intake runners have been beautifully radiused, one of the recommended mods in the Chrysler Performance tech bulletin. There are mods a guy "6BBL FLASH" did that are shown on the Victory Library site and he raced regularly, and got about 2/10ths faster times than the Chrysler Performance mods got him.
                  Also, I was REALLY disappointed that the Weiand wouldn't fit under my 70 Roadrunner N96 hood, but as part of my research, as stated above, it will fit under the aftermarket, slightly larger A12 6bbl hood scoop.
                  Paul Rossi said that intake was done at 6,500 RPMs, and another guy Jed who has a YouTube channel had 3 home built 500 cfm 2bbl carbs on a Weiand, well set up, and he has decided to go to a 2x4bbl setup because of the same reason, his cam and 500 cu in stroker need more RPM capability than the Weiand can offer.
                  I may never use mine, as I have a Bill Mitchell aluminum RB block that I'm building into a 541 stroker, and I can't see using TF 240 heads on a 541, so I'm going with the TF 270 Max Wedge port size heads, and in an attempt to keep it under my Air Grabber, I'm using the Indy ModMan intake CNC'd to MW port size.
                   
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