Bad Valve Clearance – How To Adjust The Valves The Right Way?

Bad Valve Clearance – How To Adjust The Valves The Right Way?

July 29, 2021 0 By CarGuy

If your engine is running poorly with no power and is making some weird ticking noises maybe all you need to do is to do a valve adjustment job to fix the bad valve clearance.

Valves have to have proper clearance between them and the rockers. If this clearance is nonexistent or it’s too big, some issues may start to appear.

When we are talking about engines, everything is about the perfect timing. All bits and pieces inside the engine need to work in perfect harmony in order to deliver some proper performance, and the valves are no exception to this rule.

In this article, we are going to learn everything you need to know when it comes to valve clearance. What is valve clearance? Which valve clearance is bad and which is good. We also going to get through all of the symptoms of incorrect valve clearance.

In the second part of this article, we are going to learn how to measure the valve clearance and how to adjust the valve clearance with shims. So, let’s get into this article. Just remember that this article is for adjusting valves on engines that do not have an overhead camshaft.

What Is A Valve Clearance?

The valve clearance is the gap between the rocker arm and the top of the valve stem. There are two to four valves per cylinder. One valve is the intake, the intake is usually the bigger valve, and the exhaust valve is the smaller one.

Valve clearance is important because if there is zero valve clearance the valve will stay open, and if there is too much valve clearance the valve will be completely shut.

Valve clearance is always checked when the engine is cold since the metal parts expand when running at high temperatures.

Misaligned valves can start to rattle and cause noises under the hood. This noise is caused because the valves are misaligned and they do not share the same setting on all the cylinders. That’s why valve adjustment is important.

Why Your Valves Need Adjustment?

Valves are one of the moving parts of your engine. Although everything on your engine is perfectly aligned from the factory when the car is driven and as the years go by these valves misalign over time.

Every once in a while, let’s say every 80,000 miles your valve cover needs to be removed in order to check the condition of the valves. To see the valve seals, valve stems, replace burnt valves, and adjust them to factory spec.

Bad Valve Clearance Symptoms

Bad valve symptoms can be a few and we are going to cover most of them. Most of the symptoms are connected with the engine idle and the overall performance of the engine. Also, the sounds that bad valve clearance produces.

Rough Idle

One of the first symptoms, when you have misaligned valves and bad valve clearance, is the rough idle. A bad alignment can cause your valves not to open or open too late, or open too much. This kind of work will interfere with the air and fuel distribution and also the exhaust.

All of your valves need to be properly adjusted and also the setting to be the same among them. Each valve should have the same clearance.

Valves Start To Rattle

If they are not adjusted correctly the engine will start to rattle when cold started. When it gets warmer the problem will go away and will be easier to ignore. But you shouldn’t ignore this issue because when something rattles will cause also vibrations in your cabin and will cause an unpleasant feeling.

Poor Gas Mileage

Gas mileage will suffer when the valves are not opening and closing as they used to. If the valve is misadjusted and drops the fuel inside the combustion chamber after the spark, it may cause the car to run rich and drop more fuel than it needs to in order to work properly.

More fuel will come out of the exhaust that is not ignited and may cause explosions in the exhaust and blue smoke. All these things will worsen your fuel mileage because the O2 sensors will read some values that are not the right ones for your engine.

Engine Misfires

Misfires are also one of the symptoms that go along with poor gas mileage. The car is usually misfiring and starts to work unevenly. The bangs in the cylinders are not timed and this creates uneven work. The air/fuel mixture and timing are completely messed up in this situation. This can only be solved with the valve adjustment.

Misfires can also be caused by bad O2 sensors, bad MAF sensors, bad spark plugs, and coils. So, if your engine is misfiring it is good to check some of these components.

Burnt valves

If the valves are adjusted too tight, they can burn and cause an incorrect seal of the combustion chamber. When valves are not adjusted properly, they can have extremely low tolerances when they open and the exhaust gasses will not be able to completely escape the chamber.

By not allowing the exhaust gasses to escape the combustion chamber, heat is going to be developed and also too high compression. And all these things may cause the valve to burn or chip.

Loss Of Compression

If the valves are too tight, your engine will probably going to have some compression issues. If the valves don’t seal completely there will be a lack of compression in the compression chamber and this can potentially cause some other issues as well.

Since there is a lack of compression there will be less and less power from that cylinder. When you face this issue, the best thing to do is to do a compression test. Loss of compression rarely occurs when the valves are not adjusted properly. Loss of compression mostly happens when there is a lack of seal in the engine head valves. This may be caused by a burnt valve or some related issue like a valve guide seal and bad valve guides as well.

What Happens If Valve Clearance Is Incorrect

If the valve clearance is incorrect, you are probably going to face most of the symptoms above. In the worst-case scenario, you may end up with a burnt valve and poor fuel mileage.

That’s why it is very important that your valves are adjusted properly. Later in this article, we are going to learn how to adjust valves with a valve adjustment tool. This is a fairly simple process and is extremely easy to do.

How To Tell If Valves Need Adjusting

After you hear a light tapping noise coming from the engine, you know that there is something going on with the valves. If they are loose, you can hear them and spot them easily.

If you remove the valve cover you will notice how the rocker arms are loose and they do not have the proper clearance with the valve. And if your engine is above 80,000 miles for sure it needs some adjusting in order to bring it back to proper working order. This can be a part of your next small tune up if you haven’t done any preventive maintenance already on your car.

Valve adjustment Benefits

Valve adjustment benefits are very big. First of all, when your valves are properly adjusted the engine will run smoothly and you will enjoy driving. Secondly, the wear and tear will be reduced to zero and your valves will not going to suffer. Thirdly, you will enjoy better fuel mileage and overall, you will improve your engine lifespan.

Valve adjustment is important if you want to have an engine that will last for many miles and will serve you for long years.

Valve Adjustment Procedure

In order to adjust the valves, you need to have a proper tool in order to tighten them up. A valve adjustment tool can be found on Amazon for really cheap. You will also going to need a feeler gauge in order to measure the distance between the valve and the rocker.

Feeler gauges are necessary for you to know the sweet spot and adjust all the valves of your engine the same way. We are going to attach a video of how this procedure is done the proper way.


In this article, we have learned what is valve adjustment. And why it needs to be done in order for the engine to work properly.

Valve adjustment is important if you want your engine to run in perfect harmony. And all of the cylinders to work properly. By doing this, you will prevent future problems like burned valves. And also bad valve seals by doing just a simple job.

One of the other benefits of valve adjustment is that your engine will stop producing that unpleasant noise that you don’t want to hear.

Valve adjustment kits are also fairly simple to find online and are readily available. You just need to know the procedure which is not that complicated when you figure it out the first time.