1. Dustermantommy

    Dustermantommy Member

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    Got My 340 rebuilt two years ago with a lot of good parts set of X heads cast iron, custom dome Ross Racing pistons big cam and value springs and so on. It made 490 hp @ 6900 rpm on the engine dyno at the shop In Jupiter FL. J & J Balancing that built it. Wow I was very excited to put it in my 70 duster back half car for some Bracket Racing. (Just retired from the FEC railroad after 35 years ready for some travel with my car to all the grate drag strips east to west) but I’m stomped? It took a year to finish the car and now it won’t start got spark, fuel, Compression it just sputters like it only fires on some cylinders. Got all new MSD 7-Al box, coil, distributor checked all plugs all have fire 1 8 4 3 6 5 7 2 , checked TDC on #1 multiple times. I even got a new old school points distributor and hot wired to the battery. Still got the same problem. I can sweep the timing (turn the distributor 180) with no back fire, got to be a timing Issue. Love my Mopar but I’m at the end of my rope
     
  2. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    Basics are fuel, compression, spark

    Compression: Have you checked? Cam timing, dry cylinders with no break in, fuel washed off cylinder walls, incorrect valve adjustment, or wrong push rod length. Run a compression/ leak down test

    Fuel. Make sure it is actually gasoline and FRESH. Obtain some known fresh gas in a squirt bottle to hand prime carb throats

    Spark. Must be adequate spark and at the right TIME. You can check timing with a light "on the starter." With MSD you should have MASSIVE spark. CHECK SPARK NOT while jumpering starter relay, but rather WHILE USING THE KEY to crank the engine. That is important

    Google and be aware of "rotor phasing."

    Are the plugs fouled with fuel?
     
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    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      HOW DID you install distributor and set timing? You need to be on compression stroke Some timing lights "do not like" MSD
       
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      • jay27

        jay27 Well-Known Member

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        Im not sure how to diagnose sputters , however I would look at what has changed since the dyno.
        Fuel , is the fuel fresh , does the carb have a stuck needle and seat
        Ignition , what has changed , plugs, gap , coil , MSD box
        You can move the distributor 180 degrees and it does not backfire? confused by that.
        You have a good response above and if possible post a video, good luck.
         
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        • jay27

          jay27 Well-Known Member

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          Is it responsive on throttle or not at all , is the sputter an idle situation or? what does it do with throttle?
           
        • doug 371

          doug 371 Well-Known Member

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          I'm not familiar with that box but is there possibly a green loop wire to cut?
           
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          • Murray

            Murray FABO Gold Member FABO Gold Member

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            Distributer= 180* off.
             
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            • lilfontleroy

              lilfontleroy annoyinglilLeroy FABO Gold Member

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              have you tried a shot of starting fluid? I know it's not the best way to get things going, but it can help with diagnoses.
               
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              • doug 371

                doug 371 Well-Known Member

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                I bet its a new box with loop wire not cut
                 
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                • dano

                  dano Evil Handy Man

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                  Welcome and congratulations on retirement. My dad went 38 years with the BNSF starting as a track gandy working his way up to engineer. Its a crap job with crap hours.

                  You'll find lots of help and knowledge here.
                   
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                  • RammerJammer75

                    RammerJammer75 Well-Known Member

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                    Correct me if I'm wrong, but I'm pretty sure all MSD boxes you don't cut any of the loops for 8 cylinder engines.
                     
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                    • RammerJammer75

                      RammerJammer75 Well-Known Member

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                      Straight from the MSD pdf.
                      upload_2020-9-23_15-13-12.png
                       
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                      • tonysrt

                        tonysrt FABO Gold Member FABO Gold Member

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                        Are you getting 12 volts in the run position when using the point distributor. It may fire in the start position and crap out in the run position because your losing voltage. You say you hot wired to bat., are you on the positive side of coil?
                         
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                        • harrisonm

                          harrisonm Well-Known Member

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                          I agree with all above.
                          1. I would do a compression test first. One time I saw a 440 with solid lifters and the valves were adjusted so poorly that compression was practically zero on all cylinders. No compression, no running engine.
                          2. Make SURE the rotor in the distributor is pointing to the #1 spark plug tower when the engine is at TDC in #1. That means you have to be absolutely sure you are on true TDC. Remember that the timing mark tab will hit the "0" line in the balancer for #1 when the piston is at true TDC and again when the piston is at the top for the exhaust stroke. To find true TDC, turn the motor over a little at a time. When you start feeling pressure coming out of the spark plug hole, the piston is on its way up for the compression stroke. That means that the next time the timing tab hits the "0" mark on the balancer (and it will be REALLY soon), #1 is at TDC.
                          3. Make sure you have spark.
                          If you have compression, if you ensure the distributor is installed properly and if you have spark and fuel, it will run.
                           
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                          • 67Dart273

                            67Dart273 FABO Gold Member FABO Gold Member

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                            That is why I said........it is important to use the key to test spark
                             
                          • doug 371

                            doug 371 Well-Known Member

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                            Thanks...I couldn't remember exactly
                             
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                            • B3422w5

                              B3422w5 Well-Known Member

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                              Make absolutely positive you have plenty of voltage from your battery.
                              Even a little low will cause what you are seeing. Try putting a battery charger on boost hooked up to the battery and see if symptoms change.
                              MSD hates marginal voltage
                               
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                              • Dustermantommy

                                Dustermantommy Member

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                                Wow, Thanks each and every one of you for your responses it is overwhelming me how much the Mopar community is willing to help. C0B5305D-4453-45EA-A393-72BA01EBD5FB.jpeg 4EAC3155-40DA-4017-8F1D-D91C0EE11F1D.jpeg 4EAC3155-40DA-4017-8F1D-D91C0EE11F1D.jpeg C990B1C9-B731-4238-8951-640367360905.jpeg ECE2E793-FFDB-4FCE-92A4-E3E2C28C7D67.jpeg 5763C42A-6217-468E-84EF-A992313C1C19.jpeg 47D6B389-9499-43FB-BF94-C905871AF18A.jpg
                                C0B5305D-4453-45EA-A393-72BA01EBD5FB.jpeg 4EAC3155-40DA-4017-8F1D-D91C0EE11F1D.jpeg C990B1C9-B731-4238-8951-640367360905.jpeg ECE2E793-FFDB-4FCE-92A4-E3E2C28C7D67.jpeg 5763C42A-6217-468E-84EF-A992313C1C19.jpeg 47D6B389-9499-43FB-BF94-C905871AF18A.jpg C0B5305D-4453-45EA-A393-72BA01EBD5FB.jpeg 4EAC3155-40DA-4017-8F1D-D91C0EE11F1D.jpeg C990B1C9-B731-4238-8951-640367360905.jpeg ECE2E793-FFDB-4FCE-92A4-E3E2C28C7D67.jpeg 5763C42A-6217-468E-84EF-A992313C1C19.jpeg 47D6B389-9499-43FB-BF94-C905871AF18A.jpg
                                sputtering wants to start but sounds like not turning over fast enough but it’s turning over well
                                 
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                                • Dustermantommy

                                  Dustermantommy Member

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                                  Ran with box before, 7AL-3 MSD ,thanks for your help
                                   
                                • Dustermantommy

                                  Dustermantommy Member

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                                  Ya l know man bet you don’t see him much it was tuff for me to, but kept my head down and banked a lot of green and maxed out my 401 k for 27 years, it’s paying off now
                                   
                                • dano

                                  dano Evil Handy Man

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                                  Yep, as a kid I remember laying in bed hearing him come home and be gone before I woke up. I'm glad he's having a long retirement now.
                                   
                                • Dustermantommy

                                  Dustermantommy Member

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                                  Yes Railroad Retirment is not part of Social security system it is it’s own entity for all those people that paid the price of working for a RR and can be 2 or 3 times as much SS so I know he is not worried about money and thats a lot of being retired. Thanks for your help!
                                   
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                                  • Dustermantommy

                                    Dustermantommy Member

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                                    One of the first things I did took the 14 Volt battery out of the trunk and wired with a short lead to starter and IG. box no different, thanks for your post!
                                     
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                                    • B3422w5

                                      B3422w5 Well-Known Member

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                                      had this happen with a buddies new motor about 6 weeks ago. Couldnt get it to fire, acted like it wanted to.
                                      Finally looked at battery it had 12.3 volts not cranking on it.
                                      Put a charger on “ start” cranked it over, fired right up.
                                       
                                    • CRUZE 418

                                      CRUZE 418 FABO Gold Member FABO Gold Member

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                                      Why or where do I recognize the gal in the picture with you?
                                       
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