Factory tach with MSD6al.

Discussion in 'Troubleshooting & Diagnosis' started by joer, Dec 26, 2020.

  1. joer

    joer Veteran Member

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    How can I get my factory tach to work off my msd box. 79 Z/28 need help.
     
  2. sandlapper

    sandlapper Veteran Member

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  3. joer

    joer Veteran Member

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    It's an old msd-6420 box. I always ran a after market tach. The tach started to jump around. Could be the tach so i changed it. New tach still doing it. I called MSD. Might be the tach plug on the box. What i want is to not use after market any more. Why not use factory tach. What i want to know is how to connect factory tach to msd box. Using sum-850050 distributor.
     
  4. Zspoiler

    Zspoiler Veteran Member

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    There is a filter for those .If not in your manual contact MSD
     
  5. joer

    joer Veteran Member

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    I talked to MSD. He said something about cutting out filter. After you cut out filter can you splice a wire from the end to MSD box?
     
  6. COPO

    COPO Veteran Member Lifetime Gold Member

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    My MSD 6AL is a model 6420 cause I didn’t want to go digital and my brown Tach wire works on the Tach connector at the MSD box.
     
  7. sandlapper

    sandlapper Veteran Member

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    Just what he said
    that's what it says in the instructions I linked above; mid-way down page 7. "Bypass In-Line Filter"

    JMO, for a motor that's primarily street ... a good, stand-alone HEI dist is hard to beat. Hot fire & dang-near bulletproof & parts readily available. Have run HEI in CT race cars. I've also run CD boxes in CT race cars; still have spares (suggest you travel with spares as well). Ya know, before Cup went EFI, they all ran a dual-trigger dist and TWO coils & TWO CD boxes; all redundant with selectable A-B switchgear. Always brand new stuff but boxes still puke.
     
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  8. joer

    joer Veteran Member

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    My set up is the same as COPO. Old 6al 6420. I'll look for the brown wire and change the end. Plug it in and see what happens.
     
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