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66 425hp Ignition Upgrade

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  • Tom C.
    Expired
    • November 1, 1997
    • 94
    #1

    66 425hp Ignition Upgrade

    My 425 (actually 475 or so now) runs great up to 5000rpm. Anyone had any experience with the infra red points replacement system (mallory unilite) which replaces the points in the stock Delco distributor. My TI unit is gone and I'm currently running a single point distributor and stock coil. I Have been told I need a hotter spark for optimum performance above 5000rpm. I'd be interested to know what performance figures others have with their 425 motors and on what kind of gas. (I'm running 100 LL avgas).

    Anyone know where I can find a non-working TI amp to install as a dummy. I'd like everything to "look" right.
    Tags: None
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    • Trebor M #25911
      #2
      Re: 66 425hp Ignition Upgrade

      The Mallory system you want to install is a very good idea if you want preformance plus reliability. I have installed plenty of these and I hav'nt had a problem yet. You can run a hotter coil and still maintain a stock appearence. The distributor will go from having one wire to three coming out of its bottom side. This is the only outside indication that shows the modification. If you are crafty you can hide the ground wire and show only two wires like the original TI distributor had. As far as the amp goes you can purchase these at most corvette swap meets. The TI harness , if you dont have it , is expensive if it is for appearence only. good luck.
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        • Trebor M #25911
          #3
          Re: 66 425hp Ignition Upgrade

          The Mallory system you want to install is a very good idea if you want preformance plus reliability. I have installed plenty of these and I hav'nt had a problem yet. You can run a hotter coil and still maintain a stock appearence. The distributor will go from having one wire to three coming out of its bottom side. This is the only outside indication that shows the modification. If you are crafty you can hide the ground wire and show only two wires like the original TI distributor had. As far as the amp goes you can purchase these at most corvette swap meets. The TI harness , if you dont have it , is expensive if it is for appearence only. good luck.
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            • Doug Flaten
              #4
              Re: 66 425hp Ignition Upgrade

              If you can live with a few extra wires near the coil and ballast resistor, you might consider a multi-spark capacitor discharge ignition such as MSD. I installed one on my '61 dual four. I hid the ignition box behind the kick panel where there was plenty or room. The engine continually fouled plugs and missed a lot. Granted it runs rich because it needs carb work, but the MSD ignition made it idle smoother, pull harder and the plugs no longer foul out in 1000 miles. It is noticeably quicker up to the 6500 rpm red line using one set of the dual points to trigger the ignition. There is no longer the engine vibration that was noticeable when the #4 plug fouled out. It is not too intrusive and made a great deal of improvement in maintenance, performance and driveability.
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                • Doug Flaten
                  #5
                  Re: 66 425hp Ignition Upgrade

                  If you can live with a few extra wires near the coil and ballast resistor, you might consider a multi-spark capacitor discharge ignition such as MSD. I installed one on my '61 dual four. I hid the ignition box behind the kick panel where there was plenty or room. The engine continually fouled plugs and missed a lot. Granted it runs rich because it needs carb work, but the MSD ignition made it idle smoother, pull harder and the plugs no longer foul out in 1000 miles. It is noticeably quicker up to the 6500 rpm red line using one set of the dual points to trigger the ignition. There is no longer the engine vibration that was noticeable when the #4 plug fouled out. It is not too intrusive and made a great deal of improvement in maintenance, performance and driveability.
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                    • Dwight Farmer
                      #6
                      Re: 66 425hp Ignition Upgrade

                      Tom, I was curious about your experience with 100LL avgas. I used Exxon 100LL avgas a couple of years ago and my 400 horse tripower ran very rich at idle even at 1/3 avgas to 2/3 93 Amoco premium. I understand that the Reid Vapor Pressure is lower in avgas and will vaporize quicker thus creating an overrich condition. I drained it out and replaced with the 93 Amoco and it ran fine. I should note that I had an ole muscle car mechanic recurve the distributor to bring the timing up slower. I was wondering what brand avgas you used and if you got the rich idle condition with your 425 horse. Thanks.
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                        • Dwight Farmer
                          #7
                          Re: 66 425hp Ignition Upgrade

                          Tom, I was curious about your experience with 100LL avgas. I used Exxon 100LL avgas a couple of years ago and my 400 horse tripower ran very rich at idle even at 1/3 avgas to 2/3 93 Amoco premium. I understand that the Reid Vapor Pressure is lower in avgas and will vaporize quicker thus creating an overrich condition. I drained it out and replaced with the 93 Amoco and it ran fine. I should note that I had an ole muscle car mechanic recurve the distributor to bring the timing up slower. I was wondering what brand avgas you used and if you got the rich idle condition with your 425 horse. Thanks.
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                            • Bill W.
                              Very Frequent User
                              • November 1, 1977
                              • 402
                              #8
                              Re: 66 425hp Ignition Upgrade

                              Hi Dwight,

                              Just read your quiery on av gas. You are correct In stating av gas has a lower Reid vapor pressure, this means your fuel will vaporize more slowely, not faster. I too have noticed a rich idle condition when using LL 100. I will make a wild guess that the density(spicific gravity) of the fuel has been lowered a few points. This would have a direct effect on the float level in your carb.(lower S.P. equels higher float level). I first noticed this happening about five years ago. Prior to that time, I saw no differance in idle quality.

                              I no longer have the means to check fuel density, maybe one of the members can do this, if so, please e-mail me the results. Bill
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                                • Bill W.
                                  Very Frequent User
                                  • November 1, 1977
                                  • 402
                                  #9
                                  Re: 66 425hp Ignition Upgrade

                                  Hi Dwight,

                                  Just read your quiery on av gas. You are correct In stating av gas has a lower Reid vapor pressure, this means your fuel will vaporize more slowely, not faster. I too have noticed a rich idle condition when using LL 100. I will make a wild guess that the density(spicific gravity) of the fuel has been lowered a few points. This would have a direct effect on the float level in your carb.(lower S.P. equels higher float level). I first noticed this happening about five years ago. Prior to that time, I saw no differance in idle quality.

                                  I no longer have the means to check fuel density, maybe one of the members can do this, if so, please e-mail me the results. Bill
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