How much timing does vacuum advance add at idle?

If you were to put a timing light on a car going down the highway with the vacuum advance properly connected, you would be extremely surprised to see somewhere around 40-50 degrees of ignition timing.

What should timing be at idle with vacuum advance?

This can be checked with the engine running at idle with a timing light. Make sure the vacuum advance connection is removed, and now rev the engine up to around 2,500 to 2,800 rpm. Ideally, the timing now should be somewhere around 34 to 36 degrees to total advance.

How much does vacuum advance add at idle?

Next, he checked the amount of vacuum advance supplied by the can at idle. All we did was reset the initial timing at 12 degrees, and then recorded the amount of timing at idle with the vacuum can connected. This measured 22 degrees, which meant the can added 10 degrees.

Does vacuum advance add to total timing?

Under a light load and part throttle conditions, timing can be advanced. This improves throttle response and makes the engine more efficient. It also helps the engine run cooler. The vacuum advance provides this benefit BEFORE the Mechanical Advance provides Total Timing.

Does vacuum affect timing?

The ignition or valve timing may be retarded if the vacuum is steady but lower than normal. Low vacuum can be caused by low compression, intake leak or tight valves. If the vacuum is higher than normal, it's a sign of advanced timing.

How Ignition Timing Works: Vacuum and Mechanical Advance Explained!

Does vacuum advance work at idle?

Plugging your vacuum advance into a direct source will allow it to engage at idle, which is good for a number of reasons. Much like cruise conditions, engines run leaner at idle than they do under load. Again, this means the mixture burns slower and needs an earlier spark to optimize the burn.

Does manifold vacuum increase with RPM?

Since vacuum varies with load, not RPM, increasing speed gradually will keep the vacuum high. Closing the throttle makes the vacuum go high, opening it reduces the vacuum.

What happens if timing is too advanced?

When this starts to happen at the wrong time, the combustion process is off. This causes your engine to use more fuel to compensate for reduced power. Overheating: If the air and fuel mixture is ignited too soon in the combustion process, the heat generated will increase. This can damage different parts of the engine.

What rpm set initial timing?

Lighter springs allow the advance to begin at a lower rpm. Heavier springs delay the onset and slow the rate of advance. A typical mechanical-advance curve might start advancing at 1,500 rpm and achieve full advance by 2,600 rpm.

Should I run vacuum advance?

You need the vacuum advance for best performance at low throttle settings for the street as Barry said. If you were running on a circle track or a drag strip there wouldn't be a need for it because the mechanical advance would be doing the job.

Is vacuum advance ported or manifold?

The only difference between the two, is that manifold source would give you vacuum advance at idle, ported source gives you the same manifold vacuum, but only once the throttle is cracked open.

How do I adjust my vacuum advance canister?

You can easily adjust the vacuum advance of the Street Fire Distributor. Insert a 3/32" Allen wrench in the canister inlet and turn the adjustment screw clockwise until it is all the way in (Figure 2). Counter clockwise reduces the advance, clockwise increases.

How do you calculate total timing?

A: Total timing, which refers to the maximum amount of ignition timing applied to the engine, is easy enough to calculate. You get the number by adding initial timing to mechanical advance.

What is the correct timing on a Chevy 350?

The timing can vary between 2 and 12 degrees BTDC, the recommended spark plugs are different and even the plug gaps vary. In most cases starting out with 12 degrees of initial advance is about right.

What is the difference between initial timing and total timing?

Initial timing, or the 10 degrees we mentioned earlier, is your timing setting at idle. Total timing, which may be something like 34 degrees of advance, is what the timing changes to when the engine is up to speed. The reason the timing needs to change is due to the increased speed of the engine.

What rpm should full timing be in?

Rev the engine past the point where your mechanical advance is fully engaged. (Usually, 3,000 - 3,500 rpm will do it.)

What will retarding timing do?

Retarding the timing means the plug fires later in the compression stroke (closer to TDC). Retarding the timing can help reduce Detonation. However, if the spark happens too late, you will lose power.

What is normal timing advance?

Timing Advance (TA) is the variable controlling this adjustment. Technical Specifications 3GPP TS 05.10 and TS 45.010 describe the TA value adjustment procedures. The TA value is normally between 0 and 63, with each step representing an advance of one bit period (approximately 3.69 microseconds).

Does advancing timing make engine run hotter?

It can also be seen that advancing the timing increases the peak temperature (see Fig. 16.18) achieved during combustion, but tends to decrease the release temperature, while retarding reduces the peak temperature but increases the release temperature.

What are the symptoms of timing being off?

When any changes are made to the engine of a car, the ignition timing is adjusted accordingly. If not, you could experience several problems with your engine with improper ignition timing like knocking, hard to start, increase fuel usage, overheating, and reduced power.

What should vacuum be at acceleration?

Common Vacuum Test Results:

Normal Engine: On most engines, accelerate to around 2000 rpm and then quickly release the throttle. The engine should snap right back to a steady 17- 21″hg vacuum.

When the engine is at idle speed manifold vacuum?

At idle, manifold vacuum is high (although it's the highest when decelerating with the throttle closed). As engine load increases, the throttle opening also increases and manifold vacuum drops. There are two basic types of MAP sensors: analog and digital.

What causes low vacuum at high RPM?

A vacuum reading at idle that is much lower than normal might indicate leakage through the intake manifold gaskets, manifold to carburetor gaskets, vacuum brake booster or the vacuum modulator. Low readings could also be caused by very late valve timing or worn piston rings.