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Avanti bogs down under full throttle - update

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  • Avanti bogs down under full throttle - update

    My '63 w/supercharger has had alot of work done on it recently. It's automatic and if you manual shift it, it will bark between 1st & 2nd. But while it will fly, there's a problem we can't figure out. If you're running at 45-50 mph and just stomp down, it bogs or has a dead spot. However, if you manually downshift it in tandem with going full throttle, there doesn't seem to be a problem. It will also bog at 70 mph, but I'm not gonna downshift at that speed. Any ideas or suggestions would be much appreciated. [^]

    edp/NC
    '63 Avanti
    '66 Commander
    edp/NC
    \'63 Avanti
    \'66 Commander

  • #2
    what rear axle have you got?

    Comment


    • #3
      Sounds like transmission kick down is not working. It is
      a ratio thing, but if the rear gears are fairly low, there
      must be a trans or linkage problem

      Tex in Alabama












      Comment


      • #4
        I think you should try advancing the timing and see if it improves. For testing, ignore the recommended settings and advance it 5 degrees and see if it's better.

        When things are right the transition from primary to secondary should be seamless. A bog can also be caused by feeding the engine too much air or fuel before it can actually burn it. On the AFB the secondary air valve keeps that from happening. Unlike some other carbs it isn't adjustable ( at least not easily ) and will only open as engine vacuum is enough to overpower the weights on the valve. If that valve were stuck open a bog would occur but unless you go in and jam it open or remove it the valve will work as it should.

        If you had a trans problem you would get sluggish acceleration but no bog. I think the real telling symptom is the bog at 70. A foot to the floor downshift won't begin until the carb is well into opening the secondaries in fact almost at the end of pedal travel so your bogging before the trans can downshift. It would be very difficult to duplicate that timing manually so I believe the car doesn't bog because the downshift is happening a little quicker than if you just floor it and let the linkage do the downshift.

        Try the timing it's a free and easy test.

        ErnieR



        1988 "Beater" Avanti---R5388 @ Macungie 2006

        Comment


        • #5
          quote:Originally posted by bige


          Try the timing it's a free and easy test.

          He might have trouble getting more initial (and total) advance on that engine. I think it is an R1 with a blower.

          Dick Steinkamp
          Bellingham, WA

          Dick Steinkamp
          Bellingham, WA

          Comment


          • #6
            Hi Dick...I know he has a unique situation and ultimately it could be a challenge setting his car up but strictly as a test bumping the timing would either confirm or eliminate timing as issue. It may ping in the warm weather but that's another issue.

            If memory serves Ed also has a Mallory distributor.

            If I run initial timing at 4 degrees that the factory setting would equate too my car is an absolute slug. It takes 14 degrees initial to wake it up.

            As you know every car is different but Ed may be conservative on the timing because of the compression issue and timing it to keep the car from detonating may be hurting performance. The balance may be elusive but like I said cheap and easy test.

            ErnieR


            quote:Originally posted by Dick Steinkamp

            quote:Originally posted by bige


            Try the timing it's a free and easy test.

            He might have trouble getting more initial (and total) advance on that engine. I think it is an R1 with a blower.

            Dick Steinkamp
            Bellingham, WA

            Comment


            • #7
              DO you have adequate fuel pressure?

              Comment


              • #8
                quote:Originally posted by bige
                The balance may be elusive but like I said cheap and easy test.
                It's certainly worth a try.

                As we discussed, my R1 is A LOT happier with much more advance than the factory spec...and that's with today's relatively low octane fuel.

                Dick Steinkamp
                Bellingham, WA

                Dick Steinkamp
                Bellingham, WA

                Comment


                • #9
                  Yes, I have a T-bow Mallory distributor and R1 heads. We put the R2 springs in the dist that I got from Summit Racing. btw, my brother suggested it may be timing related too. Thanks![^]

                  quote:Originally posted by bige

                  Hi Dick...I know he has a unique situation and ultimately it could be a challenge setting his car up but strictly as a test bumping the timing would either confirm or eliminate timing as issue. It may ping in the warm weather but that's another issue.

                  If memory serves Ed also has a Mallory distributor.

                  If I run initial timing at 4 degrees that the factory setting would equate too my car is an absolute slug. It takes 14 degrees initial to wake it up.

                  As you know every car is different but Ed may be conservative on the timing because of the compression issue and timing it to keep the car from detonating may be hurting performance. The balance may be elusive but like I said cheap and easy test.

                  ErnieR


                  quote:Originally posted by Dick Steinkamp

                  quote:Originally posted by bige


                  Try the timing it's a free and easy test.

                  He might have trouble getting more initial (and total) advance on that engine. I think it is an R1 with a blower.

                  Dick Steinkamp
                  Bellingham, WA

                  edp/NC
                  '63 Avanti
                  '66 Commander
                  edp/NC
                  \'63 Avanti
                  \'66 Commander

                  Comment


                  • #10
                    Good question - how do you check it?. And, would the car otherwise run good with inadequate fuel pressure? I have a spare R2 fuel pump.

                    quote:Originally posted by curt

                    DO you have adequate fuel pressure?
                    edp/NC
                    '63 Avanti
                    '66 Commander
                    edp/NC
                    \'63 Avanti
                    \'66 Commander

                    Comment


                    • #11
                      Sorry. dunno.

                      quote:Originally posted by tluz

                      what rear axle have you got?
                      edp/NC
                      '63 Avanti
                      '66 Commander
                      edp/NC
                      \'63 Avanti
                      \'66 Commander

                      Comment


                      • #12
                        You may have a point. No one I know of except the long defunct Studebaker dealer service dept seems to comprehend how the carb and trans linkage interact. I can't understand it from reading the shop manual either. Guess I shoulda bought a 4-speed...[xx(]

                        quote:Originally posted by Flashback

                        Sounds like transmission kick down is not working. It is
                        a ratio thing, but if the rear gears are fairly low, there
                        must be a trans or linkage problem

                        Tex in Alabama












                        edp/NC
                        '63 Avanti
                        '66 Commander
                        edp/NC
                        \'63 Avanti
                        \'66 Commander

                        Comment


                        • #13
                          If you had poor fuel pressure you would not have a momentary
                          bog but a loss of power that would get worse as you tried to build rpm. Low enough fuel pressure and you wouldn't be able to get up to 70. If you are experiencing a drop in power to the point that the engine almost dies you might have fuel pressure issue. If you can get acceleration up to redline once you are past the bog pressure is ok



                          1988 "Beater" Avanti---R5388 @ Macungie 2006

                          Comment


                          • #14
                            quote:Originally posted by edpjr

                            My '63 w/supercharger has had alot of work done on it recently. It's automatic and if you manual shift it, it will bark between 1st & 2nd. But while it will fly, there's a problem we can't figure out. If you're running at 45-50 mph and just stomp down, it bogs or has a dead spot. However, if you manually downshift it in tandem with going full throttle, there doesn't seem to be a problem. It will also bog at 70 mph, but I'm not gonna downshift at that speed. Any ideas or suggestions would be much appreciated. [^]

                            edp/NC
                            '63 Avanti
                            '66 Commander
                            Sounds like the adjustment of the rod to the transmission is out of adjustment so it's not kicking down to second. WOT in third at lower RPM will cause a bog. With the stock rear, it should kick down even at freeway speeds.

                            JDP/Maryland
                            JDP Maryland

                            Comment


                            • #15
                              I've apparently got some other problem. Adjusting the rod didn't fix it. Still investigating...[?]

                              quote:Originally posted by JDP

                              quote:Originally posted by edpjr

                              My '63 w/supercharger has had alot of work done on it recently. It's automatic and if you manual shift it, it will bark between 1st & 2nd. But while it will fly, there's a problem we can't figure out. If you're running at 45-50 mph and just stomp down, it bogs or has a dead spot. However, if you manually downshift it in tandem with going full throttle, there doesn't seem to be a problem. It will also bog at 70 mph, but I'm not gonna downshift at that speed. Any ideas or suggestions would be much appreciated. [^]

                              edp/NC
                              '63 Avanti
                              '66 Commander
                              Sounds like the adjustment of the rod to the transmission is out of adjustment so it's not kicking down to second. WOT in third at lower RPM will cause a bog. With the stock rear, it should kick down even at freeway speeds.

                              JDP/Maryland
                              edp/NC
                              '63 Avanti
                              '66 Commander
                              edp/NC
                              \'63 Avanti
                              \'66 Commander

                              Comment

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