Do you that a Vacuum Advance Controls your Vehicle’s Mechanism?
For many people, vacuum advance is a mystery, where in reality, it is very simple. A vacuum advance can affect the timing by adding advance when your vehicle moves down the highway to help increase fuel mileage.
Vehicles don’t normally run on the manifold vacuum but on the ported vacuum, which comes only at part throttle. At the same time, a manifold vacuum is only available when the engine is not under a load or at an idle.
The main thing that has confused many people is not about how a vacuum advance works or why the engines have only one distributor, but their main concern is which vacuum port to hook one up to on the carburetor and why?
What is a Vacuum Advance?
The vacuum advance is an ignition timing control mechanism that is built into distributors. The vacuum advance is made up of
- A vacuum canister,
- A linkage, and
- An advance plate is attached to the trigger mechanism inside the distributor.
How does Vacuum Advance Work?
When the engine vacuums rise, it pulls on the diaphragm inside the canister. The diaphragm is connected to the advance plate with the help of linkage. The movement of the linkage rotates the trigger mechanism. This causes the ignition to be triggered sooner.
What Happens if Vacuum Advance doesn’t Work?
There will be a time when deterioration will reach the point that vacuum advance will no longer adjust the timing. This will cause a vehicle to be reluctant when the engine attempts to move its weight. In addition to this lack of power, a vacuum leak can also cause the engine to idle roughly or even stall.
When should Vacuum Advance Start?
You can start the tuning process by setting the initial timing to at least 15 degrees BTDC only if your engine idles at 10 inches Hg or less. Remember, if your vehicle is equipped with an automatic transmission, then putting it in gear may pull the manifold vacuum down.
How do you Know if your Timing is too Advanced?
Symptoms of incorrect ignition timing are poor fuel economy, sluggish acceleration, hard starting, backfiring, or “pinging” or “spark knock.” Too little spark advance will cause low power, bad gas mileage, backfiring, and poor performance.
What are the Symptoms of Bad Timing?
Symptoms of a Bad or Failing Timing Belt
- You Hear A Ticking Noise Coming From The Engine.
- Your Car’s Engine Won’t Turn Over.
- You Notice An Oil Leak Near The Motor.
- You Experience Exhaust Issues.
- Your Revs Start Acting Up.
Which is Better Mechanical or Vacuum Advance Distributor?
Vacuum advance gives you great fuel economy and better engine performance because of raised timing during the periods of low speed like gear shifting or gear stop. In comparison, advanced mechanical timing gives you better engine performance in high-speed applications like race car driving.
How do I Adjust my Vacuum Advance?
An adjustment to the vacuum advance is vital if spark knock occurs under part throttle. Thie adjustment is made by inserting the 3/32” Allen wrench into the vacuum advance canister port and turning it counterclockwise. Test-drive the car and repeat the adjustments until the spark knock is eliminated.
How does Vacuum Advance affect Performance?
Timings can be advanced only under a light load or part throttle conditions. It improves the throttle response and also makes the engine efficient. This helps the engine run cooler. Also, the vacuum advance provides this benefit even before the mechanical advance gives total timing.
The vacuum advance distributors are very good for street vehicles. It does not affect full-throttle power. They provide no benefit for engines that spend most of their life at high rpm (race engines).
Does vacuum advance add to total timing?
Yes, the vacuum advance will give you this benefit even before the mechanical advance will provide total timing. The vacuum advance feature has NO EFFECT on full-throttle power. They provide no benefit for engines that spend most of their life at high rpm (race engines). A vacuum advance unit can add up to 15 degrees of advance.
Do you need to Run Vacuum Advance?
It depends on your idle vacuum, and you may need an advance that can work with your level of vacuum. If you have a low vacuum, you need a fully deployed can at a low vacuum. You also need to limit the total amount of vacuum advance.
Bottom Line
There is a tiny silver can on the side of most distributors, which is easily the most misunderstood component of the vehicle. This is feared by many people and ignored by much more, and the vacuum advance can is a vital component of the car’s ignition platform that provides both performance and economy,
Leaving it unplugged is akin to throwing free engine efficiency straight down the drain.
