Engine valve adjustment


#1

I see some times in this forum people say their car isn,t running smoothly etc. Some tell them they need the valves adjusted as they are to tight. I have never heard of valves getting tighter as an engine wears,I always found there is more slack as they wear. I am 81 years old now so the last valves I adjusted were on a 92 Honda accord 4 cyl. I didn,t adjust them because they were too tight, just the other way around. Am I out of touch with something here ? I am now the owner of a 06 Honda CRV.


#2

Over a long period of use the valve seats can get pounded into the head by the valve itself. This will result in the valve moving closer to the camshaft, or getting tighter.

It’s not at all uncommon, and without adjustment will burn the valve.


#3

Frankly, I am surprised modern cars don’t have self-adjusting valves, like one of my motorcycles. If I am not mistaken, checking valve adjustment is part of the timing belt job on most cars that have timing belts. On cars with timing chains, I don’t know anyone who does valve adjustments unless a problem arises.


#4

Modern cars do have self adjusting valves. They’re called “hydraulic” valves because the lifters/tappets use oil encapsulation to continually maintain minimum play in the valvetrain. They’re designed such that basically, when the lifter is unloaded oil is allowed to flow into a cavity between two parts of the lifter, expanding it. When the lifter is mechanically “loaded” by the cam, the passage is shut off and the fluid becomes as part of the lifter. The only adjustment is at installation, adjusting put the lifter assembly at a specificed oint within its length range.


#5

From zero to 60,000 miles the valve face can wear faster than the stems, making the valve lash tighter. It doesn’t always happen but it has to be checked for, or else maybe bad things happen.


#6

The 2006 Honda CRV has adjustable valves, to be inspected @ 110,000 miles.


#7

Honda, I am a couple years younger than you and this phenomenon of the valve lash getting tighter with age caught me off guard. After 306,000 miles on an 86 Tercel 4wd wagon, a valve burned because the lash got too tight. Before that, it seemed to me that the lash got looser with age and miles. I blame unleaded gas for that.

Leaded gas protected the valve seats. One of the big controversies when leaded gas was outlawed was that valve seats would not be protected anymore. Hardened seats were supposed to be the answer, but I guess it wasn’t the complete answer.

All in all, outlawing leaded gas was a good thing, I don’t want to give the impression that I want to see leaded gas brought back. In the leaded days, that Toyota would have probably not lasted more than 150,000 miles, if that.


#8

Thanks fellows for your answers about valve adjustments & your explanation of how they can get too tight. I would of thought the wear on the valve stem would be at least equal to the amount the valve seats would flatten, but looks like I am wrong on that. Thanks again, no comment really needed on this. Honda Bill


#9

One more thing, in our day, cylinder heads were made from cast iron, now they are aluminum.


#10

There’s also such a thing as valve stem stretch and this is especially applicable to exhaust valves.
A near red hot valve stem on a valve being slammed onto its seat repeatedly will cause a certain amount of stretch which in turn narrows the lash.


#11

Folks notice loose valves because of the noise. They don’t notice tight valves unless something really goes wrong.