How To Adjust Vacuum Advance On Hei Distributor

Vacuum Advance On Hei Distributor

How To Adjust Vacuum Advance On Hei Distributor? A star-shaped wheel in the central shaft passes in front of a magnetic pick-up in the high-energy ignition (HEI) system.

The star point emits a pulse that fires the coil every time it passes close to the pick-up. The coil of the distributor is a very important part and can be found in the cap. The magnetic pick-up switch is housed in a module in the distributor. To power the module, the distributor just requires one wire.

Each time the stay wheel creates a pulse, the module sends a voltage to the magnetic pick-up, which the stay wheel interrupts. This pulse is redirected to the module, which connects the coil and ignites the starter motor.

The vacuum advance on the HEI controls the distributor’s base. As a result, when the engine is start, the distributor will be semi-retarded.

The resulting vacuum rotates the base plate band, increasing the spark progress. When the engine is start, the RPM rises to over 2000rpm, at which point the mechanical advance kicks in, increasing the advance to 32 degrees.

How Do You Change The HEI Distributor’s Vacuum Advance

The vacuum advancement on HEI distributors (high engine ignition) is one of the first and most important changes for optimizing engine performance.

So, how do you change the HEI distributor’s vacuum advance? The steps below will show you how to do it.

  1. Adjust the mechanical timing of the engine by detaching and reconnecting the vacuum advance hose at the distributor. The power lead should then be connected to the vehicle’s battery.
  2. Disconnect and release the distributor hold-down nut. Heat the engine up by starting it and allowing it to reach the optimum operating temperature.
  3. Use the timing and turn on the distributor. 
  4. Tighten the distributor bolt after making all necessary adjustments. Increase the engine speed to 2000rpm while your assistance watches the time on the harmonic balancer. Make a note of the time settings. The vacuum advance hose plug should then be removed and reconnected to the distributor.
  5. The vacuum advance hose should be remove from the carburetor. Attach the long hose vacuum gauge to the carburetor’s vacuum advance port to continue.
  6. While driving the vehicle, have your assistance look at the maximum amount (not vacuum). When the engine is running at a standard highway pace, the speed is indicated on the gauge.
  7. Bring the vehicle to a safe stop, then engage the brakes and turn off the engine. Link the inductive pick-up of the timing light to the number one spark plug wire and the power lead to the vehicle’s battery.

Vacuum Advance And Its Working

Vacuum advance is an ignition control system that modulates the sparks automatically based on the vacuum in the intake manifold. When a vehicle’s engine isn’t operating at full capacity, vacuum advance offers the extra refining that is require.

There are three parts to vacuum advancement:

a linkage, a vacuum canister, and an advanced plate

Vacuum advance is an important part of the ignition platform because it provides both performance and efficiency. Leaving the vacuum advance unplugged equates to a loss of free engine efficiency.

  1. Make that the vacuum pump is connect to the distributor vacuum advance and has a gauge. Start the car and increase the revs to 2000, with the help of your assistance. Pump the vacuum to the same level as the reading from the driving test in step 5.
  2. Remove the vacuum pump and insert a 3/32 Allen wrench into the port where the hose clamps on the vacuum advance. In the vacuum advance, there is a little adjustment screw. To lower the vacuum advance, turn the screw clockwise, and to raise the vacuum advance, turn it anticlockwise.
  3. Reconnect the vacuum advance hose to the carburetor after removing the vacuum pump and timing light.


Delco Remy, a division of General Motors, develope the high-energy ignition (HEI) electronic ignition system. The majority of HEI systems include a distributor cap with a fit ignition coil. Intake manifold vacuum advance is an ignition timing adjustment system that changes the instant a spark occurs.

Only automobiles with partial throttles have vacuum advances. As a result, they are not in racing automobiles, which have a full throttle. Vehicle performance is improve via vacuum advance. For instance, it has a significant impact on how quickly cars accelerate and climb slopes. Protection Status
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