How to Adjust Vacuum Advance on HEI Distributor

by Linea Lorenzo

The vacuum advance on a HEI distributor is often one of the first adjustments for improved engine performance. This post will explain how to adjust your vacuum advance and some techniques you can try to make it easier.

Vacuum advance is especially useful in colder climates as it allows the engine to start more easily from a cold, congested intake manifold.

Make sure your vacuum advance is hooked up correctly. Make sure the proper number of turns are on it for optimal performance.

How do you set a vacuum advance HEI?

How do you set a vacuum advance HEI?
How do you set a vacuum advance HEI?

Vacuum advance is important to the performance of your vehicle. It's one of the many factors that will affect how fast your car accelerates, how well it can get up hills, and whether or not you have a stable idle. If you're new to cars I'm sorry for this introduction but if you want more information about vacuum advance hei please keep reading. You may be wondering what does "hei" stand for? Well, in simple terms hei stands for high-energy ignition systems which are used on some vehicles because they produce higher outputs than other types of ignitions do.

You just set the vacuum advance linkage to point at 26 degrees before top dead center. The easiest way is with a timing light.

How do I adjust my adjustable vacuum advance?

There's a good chance that you've never heard of an adjustable vacuum advance, and if you're like me, you may not know what it does. I always thought the timing was set by how much gas was in the tank when I filled up, or maybe the time on my odometer. But there's actually more to it than just those two things! The adjustable vacuum advance is responsible for regulating your car's idle speed and controlling engine load at different speeds while driving. It controls how quickly your engine responds to changing demands from the driver and maintains balance between fuel consumption and performance. If this sounds hard enough to understand, don't worry- we'll go through everything step by step here!

  1. Check to see if there is any damage to the vacuum advance
  2. Adjust the vacuum advance by turning it clockwise to increase or counterclockwise to decrease
  3. Test drive your car after adjusting - you will notice a difference in performance
  4. If you are still experiencing problems, consult with an auto mechanic for additional help
  5. Remember that adjustable vacuum advances are not designed for racing conditions and should be used only when necessary

The first thing you need to do is remove the vacuum advance from the car. Find it, and disconnect it from all other parts of your car. It should be a long piece with two wires attached to it.

Do you set timing with vacuum advance?

The answer is that it depends on the engine. If you are running a stock carburetor, then the timing will be close to 12° BTDC. But if you have an aftermarket dual-plane intake with high-rise heads and custom camshafts, your vacuum advance may need to be advanced as much as 18° BTDC. So which one should you use for your application? It's best to consult Engine Builder Magazine or ask someone who knows more about these types of engines than I do!

Vacuum advance is used to control engine timing. It has the effect of advancing the timing, which adds more power and torque at lower rpms.

How many degrees does vacuum advance add?

The number of degrees that vacuum advance adds to the intake timing is dependent on the camshaft. The more aggressive the cam, generally speaking, the more degrees it will add. For instance, a stock cam with vacuum might only be 12-degrees while an aftermarket grind could have as much as 30-degrees added with vacuum. However, if you are using nitrous oxide or other power adding devices this can alter what your engine needs so always consult your tuner!

The vacuum advance is a mechanism installed on car engines that advances the timing of the spark. When you accelerate, it adds around 10 degrees to the engine's firing angle and when you decelerate, it subtracts around 10 degrees.

How do you test a vacuum advance on a HEI distributor?

A vacuum advance is installed on the HEI distributor to increase engine response at low RPMs. It's common for this device to wear out or break, but it can be easily tested with a vacuum gauge. All you need to do is attach the gauge and check the reading against what it should be. If your vacuum reading doesn't match up, then you may have found the problem! This guide will walk you through all of these steps in order to test your HEI distributor for vacuum leaks.

  1. Remove the vacuum advance from the distributor
  2. Connect a vacuum gauge to the vacuum port on the distributor
  3. Rotate engine until it reaches operating temperature
  4. Observe how much time it takes for the manifold pressure to drop below 10 inches of mercury (inHg) and then return to normal
  5. Record this as your baseline reading, which is typically around 15 minutes but may vary depending on your engine type and age
  6. Disconnect vacuum gauge from distributor and install new or rebuilt vacuum advance in reverse order, with gasket facing down towards intake manifold

To test the vacuum advance on a HEI distributor, you'll need to touch it to make sure that it's warm. This tells us if there is power flowing through the system.


The vacuum advance on a HEI distributor is adjusted by turning the screw located at the bottom of the distributor. Turn clockwise to increase and counterclockwise to decrease the amount of vacuum advance, which will change how quickly your engine starts up or accelerates from idle. Use this information as you adjust your own distributor so that it optimizes performance for any driving situation. If you need assistance with adjusting your car's vacuum advance, contact our certified technicians today!

About Linea Lorenzo

Linea was born to love drawing and just a few tech gadgets. While not working or sleeping, he often spends hours to look through the coolest, latest gadgets at different shopping sites, drooling about them. He also likes to keep things clean and tidy - now that the reason you see so many cleaning devices and electronics reviews at Ah yes, he made the site also just for that. Occationally, he invited friends to share their expertise around here too. Linea received Bachelor of Arts in Arts & Letters at Sacramento State University.

Thoughts on "How to Adjust Vacuum Advance on HEI Distributor"

You can Get FREE Gifts. Furthermore, Free Items here. Disable Ad Blocker to receive them all.

Once done, hit anything below