Knew knocking sound after adjusting valves

[Mike Banks]

Sounds as though your valves are wrongly adjusted or your camshaft timing has altered.

Hard to say. One mistake is to adjust the valve tappets to the proper settings, run the engine, then re-torque head bolts as suggested in many manuals. If you do this, then you need to re-set the tappets to the "Set when hot" clearances before re-starting the engine, and sometimes exhaust valves have a different tappet clearance to that of inlet valves.

[kev_rm]

Wait - did you replace the headgasket without adjusting the valves?

[Compass790]

Originally Posted by kev_rm

Wait - did you replace the headgasket without adjusting the valves?

Well spotted! Rereading the O.P. that's what it sounds like. If so JimBunyards suggestion he got used to the wrong sound would fit. Anyway sounds like he found the v/v clearances were out but not sure wether that was his initial adjustment or after the recheck.

If they were too tight that could explain fuel in exhaust as well, possibly, since he has new injectors.Lucky the O.P. didn't put too many hours on it, not too kind on v/v's & seats if no clearance

[a64pilot]

The reason you can’t usually hear valve train wear is that the valve train shouldn’t wear, what wears is the actual valve itself, it wears into its seat meaning as it wears the valve clearance goes away, a valve train only makes sound when there is clearance, so as the valve wears the clearance goes away, the problem with tight valves is that they eventually get held slightly open and the resultant high temperature air that leaks past burns the valve and it will no longer seal well.

Almost all valves are adjusted cold, in theory the clearance you establish when cold mostly goes away when the engine is hot and running hard.
Way back in the day of push rod racing motors, people would stop after a hot lap and as quickly as they could adjust the lash to zero, in theory they were then getting just a touch more lift and airflow and HP.
Most likely didn’t really matter but in racing people will try for any tiny gain they can get.

[jamhass]

There could be an issue with setting the clearance. I was taught (too long ago to cite) to set valves as go/no go, rather than setting "to spec." By "to spec" I mean using the "spec" (say .015) feeler gauge in the gap and "setting" the clearance. A better way is after setting "to spec", checking with feelers on both sides. The bigger (.016) should not go, the smaller (.014) goes in easily. This avoids errors.

[phorvati]

Thanks guys. I think its fine. Sorry for being vague. I replaced head gasket in June 2018. Never had a chance to adjust the valves. Engine ran fine at the time and adjusting valves never crossed my mind. I put 10H of engine run time in 2018. I re-torqued head after about 20H. Sometimes in June 2019. I was at about 50H for 2019 when i decided i should probably adjust the valves. Below is the section right out of the ESD 442 manual.Some valves almost had no play. And some were too loose. Anyhow she runs good now. And sound seems to be gone or I might have gotten used to it by now as it was that faint.

I guess human hearing is better at detecting a change in sound then listening for a sound itself. I was pretty in tune with the engine sounds. and when you hear a new one, its only right to question it and try to understand it.

[a64pilot]

Originally Posted by jamhass

There could be an issue with setting the clearance. I was taught (too long ago to cite) to set valves as go/no go, rather than setting "to spec." By "to spec" I mean using the "spec" (say .015) feeler gauge in the gap and "setting" the clearance. A better way is after setting "to spec", checking with feelers on both sides. The bigger (.016) should not go, the smaller (.014) goes in easily. This avoids errors.

You know that go/ no go gauges are widely available? They are made so that each leaf has two different thicknesses, thicker usually about 1” in from the tip.
https://youtu.be/OfFY4Hwoopg

[mvweebles]

Originally Posted by phorvati

Never had a chance to adjust the valves. Engine ran fine at the time and adjusting valves never crossed my mind.

Good to know. Frankly, I'm amazed the valves were close enough after having the head off an installing new head gasket. If I were in your shoes, I'd count myself lucky.

[Compass790]

Originally Posted by phorvati

Thanks guys. I think its fine. Sorry for being vague. I replaced head gasket in June 2018. Never had a chance to adjust the valves. Engine ran fine at the time and adjusting valves never crossed my mind. I put 10H of engine run time in 2018. I re-torqued head after about 20H. Sometimes in June 2019. I was at about 50H for 2019 when i decided i should probably adjust the valves. Below is the section right out of the ESD 442 manual.Some valves almost had no play. And some were too loose. Anyhow she runs good now. And sound seems to be gone or I might have gotten used to it by now as it was that faint.

I guess human hearing is better at detecting a change in sound then listening for a sound itself. I was pretty in tune with the engine sounds. and when you hear a new one, its only right to question it and try to understand it.

Very wise move to investigate a change in sound as you say. Saved my engines bacon noticing a sound change more than once.
May have saved your valves & seats from long term damage.
Quite big valve clearances & most unusual to have the same clearance hot & cold AFAIK.
Our little yanmar is 0.2mm cold for instance, almost 1/2 the gap of yours, not that I'm suggesting you deviate from the manuals settings.
Thanks for explaining the sequence of events.You can tell a lot from engine noises, with experience that is.
Good to hear it's Aok