Suspected TI issue - 1971 LT1 - original TI parts - NCRS Discussion Boards

Suspected TI issue - 1971 LT1 - original TI parts

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • James G.
    Very Frequent User
    • August 22, 2018
    • 800

    Suspected TI issue - 1971 LT1 - original TI parts

    Last weekend I drove to a local show and after drove half an hour or so up to another corvette shop, when going to leave 20 minutes later the car would not start, at first I though maybe it was flooded, as when warm it is easy to flood on a restart. No dice, even after a half hour wait, it would turn turn turn and just as you let the key off it sounded like it would almost start...

    Got the truck and trailer and pulled the car to the house.
    The next morning figure I need to drop it into the shop but try the key and it fires right up, drove it about 10 miles and there seems to be a misfire under partial acceleration in the mid range.

    I have Packard 440 solid core wires with both ends soldered to the metal lugs
    Original 263 coil
    Original TI amplifier
    Original distributor
    B26 can car holds 14" at 900-1000 rpm

    I just ordered an updated solid state board for the TI box
    also have a NOS GM TI coil

    Any suggestions would be appreciated OR should I just chage the box and leave the coil, change the coil leave the box.
    I am loathe to make more than one change at a time.
    James A Groome
    1971 LT1 11130 - https://photos.app.goo.gl/zSoFz24JMPXw5Ffi9 - the black LT1
    1971 LT1 21783 - 3 STAR Preservation.- https://photos.app.goo.gl/wMRDJgmyDyAwc9Nh8 - Brandshatch Green LT1
    My first gen Camaro research http://www.camaros.org/forum/index.p...owposts;u=4337
    Posts on Yenko boards... https://www.yenko.net/forum/search.php?searchid=826453
  • Terry M.
    Beyond Control Poster
    • September 30, 1980
    • 15599

    #2
    Re: Suspected TI issue - 1971 LT1 - original TI parts

    Replace the coil. You don't need an OEM coil or even a TI coil just for the test. Easiest and least expensive trouble shooting exercise. A coil that is bad when heated up is hard to find any other way. Don't ask how I know.
    Terry

    Comment

    • Duke W.
      Beyond Control Poster
      • January 1, 1993
      • 15669

      #3
      Re: Suspected TI issue - 1971 LT1 - original TI parts

      There's a troubleshooting flow chart in the service manuals.

      I had two "no start" failures over about 60 K miles with a TI I installed on my SWC's 340 HP engine due to constant breakup of the single point ignition at high revs.

      The first TI failure was one of the main power transistor leads (It's mounted on the heat sink housing) that loops over to the circuit board popped off. I stuck it back in the via added a drop of solder than that fixed it.

      The second failure was due to corrosion on the amp connector. At that point I had learned how to blueprint the single point system to give a reliable 7000 revs, and sold the TI system to David Burroughs circa 1988 who, at the time, owned the "12-mile '67 L-88 from which the system had come from.

      So in addition to running the service manual diagnostics, check all connectors and verify that the amp ground is good.

      Since your symptoms are intermittent, my first suspect is the pickup coil wires. They're constantly exercised by the VAC and will eventually fail, sometimes hard and sometimes intermittently before a hard failure.

      When checking pickup coil resistance exercise the VAC with a vacuum pump. Pump it down and then release vacuum so it snaps back.

      Duke

      Comment

      • James G.
        Very Frequent User
        • August 22, 2018
        • 800

        #4
        Re: Suspected TI issue - 1971 LT1 - original TI parts

        Duke,
        Thanks the pick up coil information is something easy to overlook. I wouldn't have considered the work hardening of the wire from bending back and forth.


        Terry,
        Are you saying if the car will not start try another random 12 volt coil?
        Just to see if it will fire off?
        James A Groome
        1971 LT1 11130 - https://photos.app.goo.gl/zSoFz24JMPXw5Ffi9 - the black LT1
        1971 LT1 21783 - 3 STAR Preservation.- https://photos.app.goo.gl/wMRDJgmyDyAwc9Nh8 - Brandshatch Green LT1
        My first gen Camaro research http://www.camaros.org/forum/index.p...owposts;u=4337
        Posts on Yenko boards... https://www.yenko.net/forum/search.php?searchid=826453

        Comment

        • Terry M.
          Beyond Control Poster
          • September 30, 1980
          • 15599

          #5
          Re: Suspected TI issue - 1971 LT1 - original TI parts

          Originally posted by James Groome (65120)
          Duke,
          Thanks the pick up coil information is something easy to overlook. I wouldn't have considered the work hardening of the wire from bending back and forth.


          Terry,
          Are you saying if the car will not start try another random 12 volt coil?
          Just to see if it will fire off?
          Exactly James. However, Duke has given you a systematic troubleshooting guide and that is always better than changing random parts in the hopes one of them is the culprit. Best to follow Duke's advice. Usually coils that fail at high temperatures will function whn cooled off, so I may have hit to keyboard too soon.
          Terry

          Comment

          • Joseph W.
            Very Frequent User
            • February 20, 2022
            • 368

            #6
            Re: Suspected TI issue - 1971 LT1 - original TI parts

            Originally posted by James Groome (65120)
            Last weekend I drove to a local show and after drove half an hour or so up to another corvette shop, when going to leave 20 minutes later the car would not start, at first I though maybe it was flooded, as when warm it is easy to flood on a restart. No dice, even after a half hour wait, it would turn turn turn and just as you let the key off it sounded like it would almost start...

            Got the truck and trailer and pulled the car to the house.
            The next morning figure I need to drop it into the shop but try the key and it fires right up, drove it about 10 miles and there seems to be a misfire under partial acceleration in the mid range.

            I have Packard 440 solid core wires with both ends soldered to the metal lugs
            Original 263 coil
            Original TI amplifier
            Original distributor
            B26 can car holds 14" at 900-1000 rpm

            I just ordered an updated solid state board for the TI box
            also have a NOS GM TI coil

            Any suggestions would be appreciated OR should I just chage the box and leave the coil, change the coil leave the box.
            I am loathe to make more than one change at a time.
            A 263 TI coil comes original with a 1971 LT1?
            1971 coupe LS5 454/365hp
            1969 coupe L71 427/435hp
            1969 coupe L89 427/435hp

            Comment

            • Bill B.
              Very Frequent User
              • August 1, 2016
              • 303

              #7
              Re: Suspected TI issue - 1971 LT1 - original TI parts

              James,

              If you end up replacing the ignition coil (and even if you don't), it is a good idea to leave a small gap (i.e. more than 0.030") between the intake manifold and the bottom of the coil in order to minimize the heat transfer from the manifold to the ignition coil. While one does not think of the intake manifold getting "hot", it is aluminum (LT-1) and immediately after shutdown, will start getting hot from heat transfer of the heat in the heads.
              Bill Bertelli
              Northeast and Carolinas Chapters Member
              '70 Resto Mod LT-1 w/ partial '70 ZR-1 drivetrain

              Comment

              • Mike E.
                Extremely Frequent Poster
                • February 28, 1975
                • 5138

                #8
                Re: Suspected TI issue - 1971 LT1 - original TI parts

                Originally posted by Joseph Westbury (68953)
                A 263 TI coil comes original with a 1971 LT1?

                Comment

                • Joseph W.
                  Very Frequent User
                  • February 20, 2022
                  • 368

                  #9
                  Re: Suspected TI issue - 1971 LT1 - original TI parts

                  1971 coupe LS5 454/365hp
                  1969 coupe L71 427/435hp
                  1969 coupe L89 427/435hp

                  Comment

                  • Richard M.
                    Super Moderator
                    • August 31, 1988
                    • 11323

                    #10
                    Re: Suspected TI issue - 1971 LT1 - original TI parts

                    Some more info to consider...

                    The GM Diagnosis chart Duke mentioned is a valuable tool.

                    Since it worked after a overnight cool down, it's difficult to diagnose faults as it's not failing any longer. You'd need it to fail hard again to then diagnose. But yes, check items as described earlier as those are common TI issues.

                    Also ensure your ground(black wires) to the AMP is clean and solid and at the core support. Not factory, but I use toothed lockwashers at those attachment points. The Ign Coil- is hard ground on the 66+ TI System.

                    The miss you're experiencing now, may or may not be related to the original fault though.

                    But one thing that jumped at me is that you're using solid core plug wires. Is this something newly changed? According to Dave Fiedler, solid core wires should not be used with a TI System. It can cause erratic ignition behavior due to extensive overshoot & undershoot pulsing of the ignition coil output, allegedly causing adverse feedback to the TI amp. This may be specific to original Delco TI circuit boards, which you have. The K&B or LL TI Circuit boards may be affected as well, but I can't recall Dave's thoughts on those.

                    Also, in a TI system that has some type of fault, be it a pickup coil, amp, or interconnect fault or ground fault, there is a interesting artifact. When keyed from CRANK to RUN, you will ALWAYS get a one single pulse from the amp and may get a cylinder to fire off. This can be misleading, but common. It is however a slight indicator the amp and harness are talking to the coil. Also, when keyed from OFF to RUN, you also get one spark, albeit no obvious reaction as the engine isn't rotating.

                    Rich

                    Comment

                    • Patrick B.
                      Extremely Frequent Poster
                      • August 31, 1985
                      • 1995

                      #11
                      Re: Suspected TI issue - 1971 LT1 - original TI parts

                      Originally posted by Richard Mozzetta (13499)
                      Some more info to consider...

                      The GM Diagnosis chart Duke mentioned is a valuable tool.

                      Since it worked after a overnight cool down, it's difficult to diagnose faults as it's not failing any longer. You'd need it to fail hard again to then diagnose. But yes, check items as described earlier as those are common TI issues.

                      Also ensure your ground(black wires) to the AMP is clean and solid and at the core support. Not factory, but I use toothed lockwashers at those attachment points. The Ign Coil- is hard ground on the 66+ TI System.

                      The miss you're experiencing now, may or may not be related to the original fault though.

                      But one thing that jumped at me is that you're using solid core plug wires. Is this something newly changed? According to Dave Fiedler, solid core wires should not be used with a TI System. It can cause erratic ignition behavior due to extensive overshoot & undershoot pulsing of the ignition coil output, allegedly causing adverse feedback to the TI amp. This may be specific to original Delco TI circuit boards, which you have. The K&B or LL TI Circuit boards may be affected as well, but I can't recall Dave's thoughts on those.

                      Also, in a TI system that has some type of fault, be it a pickup coil, amp, or interconnect fault or ground fault, there is a interesting artifact. When keyed from CRANK to RUN, you will ALWAYS get a one single pulse from the amp and may get a cylinder to fire off. This can be misleading, but common. It is however a slight indicator the amp and harness are talking to the coil. Also, when keyed from OFF to RUN, you also get one spark, albeit no obvious reaction as the engine isn't rotating.

                      Rich
                      I have heard the idea lately that TI ignition is not compatible with solid core wires but that has not been my experience. I have run the same set of Moroso solid core wires on my 70 Corvette for 30 years without a problem, and it still has its original GM 53 year old TI amp. I also have a 67 Corvette with a GM TI amp that I use with Packard 440 wire inside the stock big block wire sheaths. It starts quicker than any Corvette I have ever had.

                      Comment

                      • Richard M.
                        Super Moderator
                        • August 31, 1988
                        • 11323

                        #12
                        Re: Suspected TI issue - 1971 LT1 - original TI parts

                        Originally posted by Patrick Boyd (9110)
                        I have heard the idea lately that TI ignition is not compatible with solid core wires but that has not been my experience. I have run the same set of Moroso solid core wires on my 70 Corvette for 30 years without a problem, and it still has its original GM 53 year old TI amp. I also have a 67 Corvette with a GM TI amp that I use with Packard 440 wire inside the stock big block wire sheaths. It starts quicker than any Corvette I have ever had.

                        Patrick, That is good to know. I've not experienced it myself but Dave was quite convincing at the time. Pethaps using different coils or other hardare are factors.

                        Rich

                        Comment

                        • James G.
                          Very Frequent User
                          • August 22, 2018
                          • 800

                          #13
                          Re: Suspected TI issue - 1971 LT1 - original TI parts

                          I mistated the coil number, I had been talking to someone about their Big block TI earlier.
                          The coil is gapped from the manifold.

                          As far as the TI and solid cores... Somewhre I recall something regarding soldering a resistor in line on the plug wires.
                          I know they used the TI with all of the Corvette racing programs in the late 60's correct?
                          I would find it difficult to believe they were running spiral wrapped linen core wires in the racing programs.
                          James A Groome
                          1971 LT1 11130 - https://photos.app.goo.gl/zSoFz24JMPXw5Ffi9 - the black LT1
                          1971 LT1 21783 - 3 STAR Preservation.- https://photos.app.goo.gl/wMRDJgmyDyAwc9Nh8 - Brandshatch Green LT1
                          My first gen Camaro research http://www.camaros.org/forum/index.p...owposts;u=4337
                          Posts on Yenko boards... https://www.yenko.net/forum/search.php?searchid=826453

                          Comment

                          • Patrick B.
                            Extremely Frequent Poster
                            • August 31, 1985
                            • 1995

                            #14

                            Comment

                            • Duke W.
                              Beyond Control Poster
                              • January 1, 1993
                              • 15669

                              #15
                              Re: Suspected TI issue - 1971 LT1 - original TI parts

                              I recall reading they were a type of wire used on light aircraft engines... likely "solid core" with near zero resistance.

                              Duke

                              Comment

                              Working...
                              Searching...Please wait.
                              An unexpected error was returned: 'Your submission could not be processed because you have logged in since the previous page was loaded.

                              Please push the back button and reload the previous window.'
                              An unexpected error was returned: 'Your submission could not be processed because the token has expired.

                              Please push the back button and reload the previous window.'
                              An internal error has occurred and the module cannot be displayed.
                              There are no results that meet this criteria.
                              Search Result for "|||"