Will MSD RTR Distributor Work With In Dash Tach?

Discussion in 'Sparky's corner' started by ChesapeakeChris, Nov 12, 2023.

  1. ChesapeakeChris

    ChesapeakeChris Well-Known Member

    Thinking of swapping my clock for an in dash tach, but not sure if my MSD RTR Distributor will work with the tach.


    The tach manufacturer states some aftermarket HEI models may generate a higher output voltage to the tach lead than what a factory GM tach can handle. It states factory GM tachs can operate on voltage ranging from 11.2v to 14.7v, but most aftermarket ignition systems generate over 18v.

    Any insight would be appreciated, thank you...
  2. john.schaefer77

    john.schaefer77 Well-Known Member

    I have the TA ready to run and it works just fine with factory tach
  3. Stage 2 iron

    Stage 2 iron 480 IRON HEAD STAGE 2

    I run a 6A box and it works fine with the factory tach
  4. 87GN_70GS

    87GN_70GS Well-Known Member

    The new aftermarket tachs feature modern circuitry with new components. They will be able to withstand higher voltages
  5. ChesapeakeChris

    ChesapeakeChris Well-Known Member

    The tach above stated it doesn't work above factory B+ (11.2v - 14.7v) and recommended a ballast to bleed off the excess voltage.

    I also found from MSD that they send a well regulated 12v signal back to the tach...
  6. 87GN_70GS

    87GN_70GS Well-Known Member

    I repair tachs for board members, been doing it for awhile. I've been inside the aftermarket tachs over the years, seen them evolve, and have even reverse engineered some. They are much more immune to higher input voltages, almost as much as my own custom designed replacement board
    Max Damage likes this.
  7. ChesapeakeChris

    ChesapeakeChris Well-Known Member

    Sounds great, thank you for the insight...

    So if my in dash tach should suddenly die, I can send it to you?

    What does that run?
  8. rallye

    rallye Platinum Level Contributor

    I have run that tach with the 6AL and HVC-L with no issues.
  9. 87GN_70GS

    87GN_70GS Well-Known Member

    Yes, replacing the circuit board and calibration runs about $50.
  10. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  11. ChesapeakeChris

    ChesapeakeChris Well-Known Member

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