What is the difference between initial timing and total timing?

Mechanical timing refers to the amount of advance that the weights, or advance assembly add to the initial. For instance, a distributor may be set up to supply 21° of centrifugal advance. Total timing is the term given to the highest amount of advance. This is when the initial timing is added to the mechanical timing.

What does initial timing mean?

The term "Initial Timing" refers to the amount of Ignition Timing applied to the engine at idle.

How do you calculate total timing?

What is total timing on a car?

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. Correctly setting it, however, involves multiple steps. First, you'll want to determine your desired total timing.

Is initial timing before or after TDC?

Let's see where this takes us. We'll break ignition timing into three categories: initial, mechanical, and vacuum advance. Initial is the easiest and you can consider this as the base timing. This is the amount of timing in degrees before top dead center (BTDC).

How To Set Initial Timing and Total Advance Timing on 350 Small Block Engine

What is initial ignition timing?

All discussion of ignition timing starts with the initial timing. This is the amount of advance at idle with the spark triggered Before Top Dead Center (BTDC). Most stock street engines call for 6 to 8 degrees of initial advance, but this is not set in stone.

What happens if timing is too far advanced?

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. Low Power: Ignition timing that is retarded too far can result in the spark plug igniting the mixture too late.

Does advancing timing increase mpg?

It advances the timing when there is vacuum in the intake manifold, except during idle (on most vehicles). It is needed for maximum efficiency because the fuel mixture burns slower when the pressure in the cylinder is lower. If it doesn't work, the engine will still make normal power but its fuel economy will go down.

Does timing change with RPM?

Basically, the PCM uses spark advance ( or retard ) to make adjusts to idle speed in order to try and hit it's target RPM at idle. So from the example above if the actual RPM is 12.5 less than the target the PCM will add 3* of advance, or if the RPM is 12.5 more than the target it will retard the timing by 3*.

What is initial timing on small block Chevy?

Depending on your cylinder heads, compression ratio, camshaft, and centrifugal advance curve in the distributor, "normal" base timing for a street high-perf small-block Chevy is somewhere in the 12- to 18-degree before top dead center (BTDC) range, with total timing at full centrifugal advance about 34 to 36 degrees ...

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 should spark advance be at idle?

In Forscan "Spark advance" is about 3 - 6 degrees and "Ignition timing" is a lot more, about 33-35 degrees. These values are at idle.

Does timing affect idle speed?

Can Timing Affect The Idling On The Car? Yes. A valve timing adjustment (for example, in a car that has a spark distributer) may result in an increase in idle speed at a throttle setting that is less efficient, in vehicles with a catalyst and valve timing settings that are different.

Will advanced timing cause rich?

If you advance your timming you will have to richin the fuel mixture, if you retard the timming then you would have to lean out your carb for it to run best.

When should you advance ignition timing?

In most cases, full advance (32 to 36 degrees) will have occurred before 3,500 rpm. An engine with camshaft duration of above 240 degrees, but less than 260 degrees of duration @ 0.050-inch valve lift, will respond well to 18 degrees of initial timing; however, the total timing will remain the same (32 to 36 degrees).

Does vacuum leak affect gas mileage?

A vacuum leak at the intake manifold gasket, in the manifold itself or any of its vacuum hose connections can lean out the air/fuel mixture and cause the engine to misfire and deliver poor fuel economy.

Will advanced timing cause hard start?

Hard starting is usually caused by an advanced ignition timing, not a delay in the ignition. In an overly advanced condition, the carb will backfire, while in an overly retarded condition, the exhaust will backfire.

What are the symptoms of incorrect ignition timing?

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.

How an ignition timing could affect engine performance?

If the ignition timing is not advanced enough, the piston will already be moving down when much of the combustion takes place. In this case we lose the ability to expand this portion of the gas through the full range, decreasing performance.

How do you increase ignition spark?

How do you set the initial time on a rebuilt engine?

You can set the timing with the engine off like this: Turn the engine to Top Dead Center on compression stroke. Turn the key to ON and rotate the distributor "backwards" to retard the timing. Now advance the timing by rotating the distributo until the points spark.