What exactly is Valve Clearances. Why they are needed!

The operation of an internal combustion engine depends heavily on valve clearances. When the valve is entirely closed, they refer to the tiny space that remains between the valve stem and the rocker arm or cam follower. Although purposely leaving a gap may seem paradoxical, valve clearances play a significant role in preserving engine longevity and performance.

Thermal Expansion: When an engine runs, its parts—including the valves and the area around the cylinder head—heat up. varied materials expand and contract at various rates in response to heat because they have varied coefficients of thermal expansion. The engine accounts for thermal expansion by leaving a tiny gap between the valve and its actuation component, such as the rocker arm or cam follower. This makes sure that even when the valve expands as a result of higher temperatures, it can still fully close.

Valve Train Dynamics: The valve train is made up of a number of parts that cooperate to govern the valves' opening and shutting, including the camshaft, rocker arms, pushrods, and valves. These parts are subjected to dynamic stresses, vibrations, and wear while in use. This dynamic movement is accommodated by the valve clearance, which acts as a buffer zone, preventing the valve from sticking or failing to close properly. It permits smooth and reliable valve operation, reducing the possibility of harm to the valve train.

Valve clearances are also important for the engine's lubrication and oil circulation. Many engines include hydraulic tappets or lifters that depend on oil pressure to keep the right valve clearance. Oil pressure creates a hydraulic cushion that lessens noise, wear, and friction by filling the space between the valve and its actuation mechanism. This guarantees efficient functioning and guards against component metal-to-metal contact.

Correct valve clearances are essential for attaining the best engine performance and reducing emissions. A number of problems can result from improper valve clearances. The valve may not fully close if the clearance is too short (or the valve lash is too tight), which would diminish compression and lead to poor combustion. Power loss, a reduction in fuel economy, and an increase in pollutants might result from this. Contrarily, excessive clearance (too-loose valve lash) can result in noisy valve operation, decreased power, and even possible valve breakage because of greater impact forces.

Thank you for watching

Craig

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#ReducingEmissions
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#EngineMaintenance
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#PowerLoss
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[PatGreen]

I really like this model as well as the closeups! This video gives a greater explanation. Well done!

[MarkAnthony-rbfp]

This makes total sense in why i kept having a misfire until i adjusted the valve lash and it idled smoothly and no more misfire afterwards.

[johnny]

The real reason is for thermal expansion and contraction. You have to allow for things to grow (pushrods, valve stems, etc.) when the engine gets hot otherwise it could hold a valve open like you talked about. Combustion temps are over 1000°F and things around the cylinders get waaaay warmer than just coolant temp, valves, piston tops, and cylinder walls are often over 1000°F even though your coolant is sitting at 220°F.

[markproulx]

Another good explanation by The Repair Specialist!

[benruether]

The common important exception is hydraulic tappets or lifters. Constant contact in those and preload on hydraulic lifters adjust via the rocker arm locking nut depending on the style of rocker arm mounting used.

[robertorochamartinsrocha]

you need gap because also the valve expend when hot ... if not you dont get the right sealing too

[mikeyd]

Only when cold surely? When they expand from the heat generated by the engine this gap will be smaller?

[cireez]

if clearance is too much does this cause a ticking sound, also does car struggle when accelerating? if clearance is improper

[aidan]

Would an interference engine run the risk of the piston hitting the valve?

[marcquirante]

I adjust mine i dunno if i do it wrong after adjusting it the fuel consumption so low and struggling to accelerate. It average kpL 70+ 😂 but i think its running lean because its hotter to run than usual. Another mistake theres 3 marker on flywheel i think i timing it wrong

[Soothsayer-rsnb]

So if the gap is larger than recommended it's not a big deal?

[ginoasci]

I have a knocking on a new triumph motorcycle with only 2000 miles.
Sounds like it’s coming from the top end.
I’m concerned about engine damage.
Could you please take a quick listen to a very short video I have on my channel.
There are only a few videos so it’s quick to find.

[Nāmarūpa]

Am I right to assume you do this when engine is cold?

[yunan]

Why does the clearance for the intake and exhaust valve differs for some engine?