Updated on May 18, 2023
You need to adjust timing on a car for many older models (those which have a distributor) to maintain the best possible performance. When timing is neglected, you can suffer poor gas mileage, less power when you hit the gas and eventually degrading problems that might keep the engine from running.
While you can get a mechanic to adjust the timing for you, it’s a fairly easy process with a quality timing light, and you’ll stand to save a lot of money when you learn to do it yourself. Before you jump in, double check your vehicle.
Most manufactured since the early 90s will have an electronic ignition timing and do not require this maintenance. In those cases, an scan tool would be a better investment.
What Is Timing?
Before we learn how to set ignition timing, we require a short lesson on how engines work. To put it simply, an engine works by using small explosions of gasoline to make pistons move up and down.
That motion spins the engine which in turn rotates the gears and spins the wheels. This is ignoring a lot of other processes that happen at the same time, but it’s the primary function of your engine.
To ignite the gasoline, we use electric spark plugs, so when we refer to a vehicle’s timing, we’re talking about making sure the spark plug fires at the best possible moment.
More specifically, we want to fire the plug right before the piston reaches its peak in the up-and-down motion. If this is a little hazy, it’ll make more sense when we talk about the whole engine cycle.
The Four Strokes
To keep an engine running, it undergoes four steps (called strokes) in rapid succession. Those strokes are called intake, compression, power and exhaust.
During intake, air and fuel are drawn into the cylinder for combustion. The compression stage is when the piston applies pressure to the air-fuel mixture.
The pressure is necessary to get a nice explosion instead of a slow burn, and this is the key to getting propulsion out of the process. The air is fully compressed when the piston is as high as possible, and this is called “top dead center.” This is the ideal time for the spark plug to fire.
The next stage is power, and it is when the explosion of gasoline forcefully pushes the piston back down to rotate the engine. The last step is exhaust where the byproducts of the explosion are ejected to make way to start the process anew.
To recap, we check the timing to make sure the spark plug is firing when the fuel mixture is fully compressed. This gives us the most power for each ignition, but over wear and tear can cause the plugs to fire slightly too soon or late. This is the reason for timing maintenance.
Understanding Timing Numbers
Before we jump into adjusting the timing, we need to know the standards. Timing adjustments are measured in degrees. You will advance or move back your timing by a few degrees during this process. You can find these numbers on the engine’s crankshaft pulley or flywheel.
They’ll be notched in ruler fashion and will be your guide to precise adjustment. You’ll want to compare the numbers you see to manufacturer recommendations.
They’re a little different for every model, and you probably won’t find this info in the owner’s manual. Instead, refer to manufacturer websites or listings from professional mechanics.
How to Use a Timing Light
At last we’re to the inductive timing light (or gun). You can set it up with the engine off to help avoid accidents. The gun should have a few plugs or clamps.
You want to attach the corresponding cables to the power and ground terminals of the car’s battery. A third wire will attach to the number one spark plug wire.
Make sure you have the right plug as this will majorly impact your timing readings. When everything is attached, start the car and let it idle. Shine the light at the timing numbers on the marks on the crankshaft pulley and you’ll see a number.
The timing gun works on a simple principle. When the spark plug fires, the current tells the gun to flash. This strobing effect should cause one of the timing numbers to appear steady as the engine runs. Compare the number to manufacturer recommendations.
Once you’ve checked the idle timing, you want to rev the engine (a friend is necessary for this part). While in neutral, rev the engine up to approximately 3500 RPMs.
As the engine turns faster, the timing will change. This creates a timing range, and you want to compare the whole range to manufacturer listings.
Changing the Timing
Now that you have the number, you know what adjustments to make. Learning how to advance timing (or regress it) is the easy part. Loosen the distributor bolt so that you can barely twist it.
You won’t be removing the distributor, but you will be rotating it. When you spin the distributor housing, you adjust ignition timing.
Make your adjustments in small increments until the timing is in the correct range. The first time you do it will take some practice, but you’ll get a feel for it pretty quickly. At this point you might be wondering which way to rotate the distributor, but that actually depends on the car.
As a rule, you advance the timing by rotating it opposite the rotor. If the rotor turns clockwise, you want to spin the distributor counterclockwise if the engine needs to advance. If this feels confusing, you can just use a small twist and a little trial and error.
When you’ve made adjustments, tighten the distributor and make sure vacuum hoses are attached and check the timing again. Rinse and repeat until the numbers are correct.
Best Timing Lights (What We Recommend)
The popular Innova 5568 is a professional quality timing light. In addition to checking ignition timing, you can also use the digital display to advance or retard timing from 0-90 degrees, and check tachometer, voltage, and dwell readings.
For convenience, the 5568 uses detachable cables, a definite advantage if you need to attach different cable styles, such as switching between ignition timing and voltage. You’ll be able to accurately test up to 9,990 RPM and switch between 2 and 4 cycle engines.
The Innova 5568 works with most ignition systems including DIS, conventional, electronic and computer controlled systems but not MSD.
Instead a cheap plastic connector, this model uses a metal clip to put around your spark plugs wires, which is a lot safer, but can get hot quickly.
The ergonomic design makes this Innova comfortable to hold, even at odd angles, and you can easily read the backlit display from almost any perspective. The included hard storage case works well to keep the unit protected when not in use.
The manual can be a little confusing at first, but most features are easy to figure out, and you will see why this unit is so popular after only one or two uses. Using a timing light is easy once you have the basics down.
The biggest complaint on the Innova 5568 is that is does not support Multiple Spark Discharge (MSD) ignition systems.
This is a common problem with timing lights, and the MSD website specifically mentions a need for MSD specific timing lights in working with their products.
Watch the readings carefully when using the tachometer functions, as the 5568 does have a tendency to “slip” the RPM synchronization under certain circumstances.
The 3555 features an advanced direct reading dial capable of up to 60 degrees of adjustment while the rotating neck’s slim design allows for superior aim at the timing mark.
You can use the 3555 to check base timing, advance or retard timing, and diagnose a no-spark condition.
It works with most foreign and domestic ignition systems and incorporates a patented skip circuitry test capable of 9,990 RPM, making this an excellent go-to tool for most vehicles.
While a delicate instrument, users report the 3555 is durable enough to handle a few small drops. The bright light makes measuring easy and the adjuster knob is smooth and accurate.
Some customers have found the lack of a trigger to be disappointing. The button works, but its automatic shutoff means less user control.
Additionally, some owners have reported issues with the light’s accuracy, although this seems to be related to whether the leads are connected tightly enough.
You don’t have to worry about a timing light that’s not compatible with some batteries (ie: 6v Volkswagens).
Perfect for a wide range of recreational and personal vehicles, this timer maintains its accuracy to an impressive 14,000 RPM. It’s compatible with all two or four cycle engines and its rugged protective sleeve can survive a blistering 1,200 degrees.
From the ample 4-foot cable to its high portability, this self-powered timing light is widely used at many mechanic schools in the country. It’s as simple as hooking up the induction wire to the #1 plug, aim, and shoot.
Despite its appearance, this light won’t function as a flashlight. It may also prove more difficult to see the mark in bright sunlight for some users, despite being quite bright.
If you only need a basic timing light gun, the Innova 3551 should be near the top of your list. The swivel head means you can get to areas that other lights require you to perform minor acrobatics for, and it has a light that is bright enough to read in full daylight.
It does not offer a lot of extra features, but will accurately check your timing up to 9,990 RPM and is priced right for the limited functionality. Just like its more advanced relative, the 5568 above, the 3551 plays along well with most ignition systems.
One simple feature that you won’t find in most timing lights is the convenient On/Off switch that allows you to use the gun without keeping a finger on the button.
The biggest complaint is that the shielded battery connectors are cheaply made, so you will have to be careful not to short it out, or use ordinary electric tape to reinforce the insulation. It is not made for commercial use, and may not stand up to a lot of rough handling.
If you’re a Do-It-Yourself type mechanic, the Actron CP7528 could very well be the best timing light for the money. It’s designed for you to use it with 6 and 12 volt systems, making it ideal for use with both cars and motorcycles.
Timing can be advanced from 0-60 degrees with the analog dial and the all-metal inductive pickup is preferred by most. The Xenon bulb is bright enough for you to use outside in full sunlight, a feature that is lacking in many of the timing lights on the market today.
See Also: Light Bulb Base Size Charts
The biggest complaint is that the CP7528 does not have a big variety of functions, and that can be an issue if you have several types of checks to perform.
While cheaper than a digital model, many users wish they spent extra for the tach capabilities of the Innova 5568.