Valve lash setting is something most drivers don’t even think about.
First you need to know if you even have an adjustable valve train for valve lash setting.
Either check your owner’s manual or call your dealer about valve lash setting.
In most cases you will not have to worry about it.
Some manufacturers advise valves should be inspected only if there is excessive valve train noise.
Others don’t mention valve lash setting clearances in their maintenance schedules.
Listen for valve noise.
Usually the need for valve adjustment is determined by their sound.
More accurately, the louder the tapping made in the valve train, the greater the need for adjustment. Properly adjusted valve lash will be quiet. Some engines will always have a light tapping noise. They should never be so loud as to overshadow all the other noises the engine makes.
Note: Knowing when the valves are too loud is a matter of experience. Not to mention, they very gradually become louder and we are often oblivious to this fact. If you’re not sure, find someone with experience to help you determine the need for adjustment.
If yours are adjustable there are some warning signs they may need attention.
- Poor running engine and low performance
- Burnt exhaust valve(s)
- Broken valvetrain components (springs, pushrods, lifters, camshaft)
- Limited or reduced lifespan of valvetrain components
- Excessive valve guide and valve seat wear
Over time the original clearances between the valve stems become bigger (with exhaust valves, the clearance can become tighter). That often leads to a clattering noise that a driver might not notice over time, because it increases gradually.
Intake valves open and close to let the air-fuel mixture (or just air in modern engines) enter the combustion chambers. Consequently, the exhaust valves allow exhaust gases to escape. Too much or too little valve clearance can result in poor performance or a rough idle. This is because the engine can’t “breathe” normally and operate at peak efficiency.
Too much clearance means the valves will likely clatter and, over the long term, cause damage to the;
- Camshaft lobes
- Rocker arms
If there’s too little clearance the valves won’t fully close, causing excessive heat, and the engine will lose power.
If your engine generates a loud clatter, it could be time for a valve lash setting adjustment. Though on some engines the valves don’t generate noise when there’s too much clearance. Loss of power could be a sign of a weak or broken valve spring, and a tapping noise could be caused by a loose rocker arm, so a clearance adjustment may not be all that’s needed. The mechanic won’t know for sure without inspecting the valves.
Adjusting valve clearance (or “lash”) requires removing the valve cover (or covers on V-type engines). It could take a fair amount of time to checking both intake and exhaust valves. It’s not a quick job like an oil change, especially on engines that have three or four valves per cylinder. Plan on at least a few hours at the shop and a charge just for the inspection.
Eliminating valve clatter is one benefit of adjusting the clearance. Also the engine will likely become smoother and more responsive. In addition, correct valve lash setting can extend the life of the valve system.
The purpose of a valve adjustment is to bring the clearance between the tip of valve stem and the camshaft lobe or rocker arm back into the specified clearance that was determined by the design engineer. As the camshaft rotates, it pushes on the valve stem. Either directly or by using a rocker arm, to open the valves inside the combustion chambers at the proper time. The valve springs will automatically close the valves.
If the valve clearance is too small, the valves will never fully close when they should be doing so and this will eventually burn part of the valve surface off and cause a constantly misfiring engine. Also, If the valves are too tight, the engine may be running rough either cold, hot or all the time. If the valve clearances get too loose, this will lead to a noisy running engine. As a result, will eventually damage the camshaft lobes, rocker arms ( if equipped ) and the tips of the valves themselves.