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Mechanical Tachometer in a later series Alpines?

Discussion in '"Stock" Alpine' started by Scotty, Dec 5, 2020.

  1. Scotty

    Scotty Donation Time

    Is anyone running one of these on their III-V? How would you set this up on a 1725 (assuming the other end of the cable goes onto what, the Distributor?) and what has been your experience with it?

    (Yes, I know I can have mine rebuilt and I probably will, but I ran across this and I'm... kind of bored today lol. Hey, my IV has a mechanical Speedo and after changing its cable it suddenly became really reliable, soooo...)

    Apologies if this belongs in the Modified Forum. I figured earlier series X going into a later series Y might be at the line of "Stock" for this, so hopefully erring on the right side :).

    Muchas Gracias, Mi Rayo de sol Amigos!
     
  2. husky drvr

    husky drvr Gold Level Sponsor

    Scotty,

    The short answer is it can and has been done. The catch is in the details - It's Not A Simple Change.

    You'll need the tachometer, drive cable, proper distributor with drive gear, proper distributor base with driven gear, the longer oil pump drive gear from a S I or II Alpine three main bearing engine, and a camshaft from an alloy head three main engine.

    The three main engine's cam and oil pump drive gears have different tooth(12) counts than the 1725 engines(11).

    The 1725 will only work with a 1725 oil pump, so to get matching parts, you'll have to disassemble your engine to change the oil pump drive gear to the early Series long pump drive gear. Now you have an incompatible cam for your newly installed pump drive gear. You have to change to an early series cam. If you are using a used cam, you should get the cam and lifters reground so they don't tear themselves apart when you start the car.

    Nothing to it,
     
  3. hartmandm

    hartmandm Moderator Platinum Level Sponsor

    I have seen pictures of another approach for driving a mechanical tach cable with a 1725. Add a gear (from an earlier oil pump?) to the 1725 oil pump. Then I think the earlier distributor mounting bracket was used. Not sure if there are mods made to the mounting bracket. Then use the 1725 distributor.

    It should be way easier to get the electronic tach working and accurate.

    upload_2020-12-6_11-8-4.png

    upload_2020-12-6_11-13-22.png

    Mike
     

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