How to Use a Dwell Tachometer

Written by don bowman
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The Tach-Dwell meter is used for tuning early model vehicles that are normally aspirated and use a standard point type distributor for ignition. The tachometer is used for tuning the carburettor, and the dwell meter is used for setting the points in the distributor. The points in the distributor are responsible for charging the distributor. The dwell is used to regulate the amount of time the coil is charged.

Skill level:
Moderately Challenging

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Things you need

  • Tache-Dwell meter
  • Set of Allen wrenches
  • Common screwdriver

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Instructions

  1. 1

    Raise the hood on the vehicle and remove the air cleaner. Attach one lead on the Tach-Dwell to the negative terminal of the coil. Attach the other lead to a good ground.

  2. 2

    Read the dial on the meter and search the scale for the particular size engine being worked on. For instance, the meter will read in three dwell scales--4, 6 and 8-cylinder. Use the appropriate dwell scale for the vehicle. An eight-cylinder vehicle should be set at 32 degrees of dwell, and it will show a progressively higher scale as the engine size decreases.

  3. 3

    Rotate the switch on the meter to the proper dwell. Start the vehicle and allow it to warm to operating temperature. Read the dwell figure on the meter. If the dwell is not within the right parameters (1 degree + or - ), the points need to be adjusted.

  4. 4

    Lift the metal window in the distributor cap and insert an Allen wrench into the recess on the points. Turn the Allen wrench either way until the proper reading is achieved. When turning the Allen wrench, if the reading is going the wrong way, stop and turn it in the opposite direction. The adjustment, in all cases, will be small.

  5. 5

    Adjust the carburettor with the Tach-Dwell attached as before with one exception: turn the switch from dwell to tache. Adjust the mixture with the common screwdriver. Watch the tachometer for indications of a rise or fall in the rpm while the mixture screws are adjusted.

  6. 6

    Turn the mixture screw on the driver's side clockwise until the tachometer shows a slight drop. Stop there and turn the screw counter-clockwise until the rpm is at the highest point and is no longer rising. Stop and turn the screw clockwise just until the rpm begins to drop. Go to the passenger side screw and perform the same procedure.

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