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formariz

Valve noise

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formariz

Can someone enlighten me as to where exactly valve noise is coming from? Is is the underside of valve hitting seat on block? But for it to seal properly doesn't that happen anyway? Or is it the stem hitting the lifter? I noticed that on Tecumseh engines that noise is more of a "tick" as opposed to Kohler's which is more of a tap.

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Kelly

Lifter hitting the cam, a tucky you have to grind the stem to get the right clearance also a small block Kohler, big Kohlers are adjustable. 

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rmaynard

I've always heard that the sound is created when the lifters hit the bottoms of the stems. :confusion-shrug:

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formariz

If all clearances are correct usually they do not make noise. Can one then assume that a noisy one is the one with too much clearance?

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Kelly

yes

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sorekiwi

It is hard to believe that closing up a valve clearance by .001 or .002 can make that much difference in the amount of noise produced.  But it does. 

 

The (auto) engines I work on at work have their clearances set at .002 and .004.  .001" too big and they rattle like hell.

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formariz

So if this is in one of the smaller engines which has no adjustment that valve needs to be replaced since it was ground too short or it is worn past it's tolerance! Yes it's incredible that such a small amount creates the noise.

Thank you everyone. It just drives me nuts not understanding or knowing the causes if things such as this. My wife has a name for this condition of mine.

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sorekiwi

Recutting the valve seat, or refacing the valve closes up the clearance some.  But on these small engines its cheaper to just replace the valve.

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Fordiesel69

The noise can come from the contact the lifter makes with the valve stem, and also if they are too loose you can hear the lifter against the cam lobe.

 

I had a spare M12 engine that had the exhaust valve way out of spec.  It ticked very loud. 

 

On the other hand I have several Tecumseh engines that are spot on, and still tick.  Go figure.  

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shorts

The valve train makes an incredible amount of noise, normally you don't hear it over the sound of the exhaust unless you have 1 valve out of adjustment and then you here it because the oise stands out from the rest of the noise. I used to work in an engine development lab and the Spintron that they used for durability testing valve trains was incredibly loud, just an engine block with a dummy crankshaft, cam and gears, no rods or pistons being spun by an electric motor. the heads could have complete valve trains or just partial systems if they were isolating specific parts like exhaust valve springs. The Spintron control system could be set up to run what ever test cycle was desired, X time at X speed or simulate the Indy 500 or Bristol or Martinsville NASCAR races or whatever test cycle the engineers wanted to run.

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formariz

Aside from obviously not opening or closing valve at the exact correct time and the annoying noise, is there a chance of any physical damage to engine due to the excessive clearance?

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sorekiwi

I think that excessive clearance does cause damage, although I don't remember ever reading or hearing any "official" theories on it.

 

But I believe that excessive clearances tend to "hammer" the pieces together.  Factory specs leave room for expansion due to heat, plus a small space for lubrication.  Excessive clearance allows the parts to accelerate hard and then slam against each other.

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shorts

How much excessive clearance do you have? A couple of thousandths shouldn't hurt anything in the engine

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formariz

Its only .002 over in the intake valve. I don't think its anything serious but i was just a bit baffled that the sound caused by it would be so noticeable.

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sorekiwi

I'm not sure I'd be replacing a valve for .002" over spec.  Do it next time the head is off.  

 

You may find that cleaning off the carbon and lapping the valve/seat might bring you back into spec.

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