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Old 14-12-2019, 14:33   #1
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Knew knocking sound after adjusting valves

Lehman 90HP. I just got around to adjusting the valves. I put around 50h since replacing head gasket in 2017. I was told valves should have been adjusted. I just went through procedure. And now i have this new sound. Sound is coming from valve cover and I am most certain it's the valves. I don't know if it's bad. I was very used to a set of sounds engine was making the past 2-3 years. And this is clearly a new one. I didnt see anything going loose, no smoke, I do have a trace of fuel out the exhaust on startup. I was hoping adjusting valves would clear that up. Is there anything I should be looking for?
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Old 14-12-2019, 15:41   #2
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Knew knocking sound after adjusting valves

Were they only just a tiny bit out of adjustment, or did you have to make a big adjustment?
Did you loosen them quite a bit?

Either way valves shouldn’t knock, valves if there is a noise it is usually a clicking or maybe a ratting type of noise, knock is usually something with a whole lot more mass than a valve.

However a knock is very often a noise that injectors that need servicing cause, they don’t make the noise, The noise is actually from excessive or fuel not atomized causing a timing change.

Have you adjusted valves before?
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Old 14-12-2019, 16:49   #3
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Re: Knew knocking sound after adjusting valves

What A64 pilot said. I'd retorque the head before you check the v/v lash if you have a torque wrench. Trace of fuel out of exhaust on startup could be just the cold weather but could be faulty injector. How many hours on motor & how long since injectors checked?
Important question as to wether you have done v/v lash before? One could have come loose.I'd describe it as a tapping sound with excessive clearance, hence the term tappets maybe?
Please post back what you find
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Old 15-12-2019, 04:53   #4
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Re: Knew knocking sound after adjusting valves

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What A64 pilot said. I'd retorque the head before you check the v/v lash if you have a torque wrench. Trace of fuel out of exhaust on startup could be just the cold weather but could be faulty injector. How many hours on motor & how long since injectors checked?
Important question as to wether you have done v/v lash before? One could have come loose.I'd describe it as a tapping sound with excessive clearance, hence the term tappets maybe?
Please post back what you find
What is meant by v/v lash? On my old BMW motorcycles, used to adjust the sideways play of the rocker arms on the shaft between the pillow blocks that bolt the head down. Same?

Curious that it started just after adjustment. And that OP calls it a "knock" vs a "tap". Could be semantics, but given the high pitch of loose valve tap, most wouldn't use "knock,". Maybe so loose the pushrods are loose? Never heard of that, but would surmise that would be a throatier sound.

Regardless, my next step would be readjusting the valves. May have missed TDC on at least one of the adjustments.
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Old 15-12-2019, 05:15   #5
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Re: Knew knocking sound after adjusting valves

Lash is the clearance, or play, between adjacent movable mechanical parts. In terms of valve lash it is the distance between the tip of the rocker arm, and the tip of the valve.
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Old 15-12-2019, 06:02   #6
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Re: Knew knocking sound after adjusting valves

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Lash is the clearance, or play, between adjacent movable mechanical parts. In terms of valve lash it is the distance between the tip of the rocker arm, and the tip of the valve.
Understood. But OP had a head gasket replaced. Part of valve adjustment is to ensure a small gap between rocker arm assembly and the pillow blocks that support the shaft. To do this, you have to loosen the head bolts, perhaps use a C-clamp to gently bring the pillow blocks together, then re-torque the head bolts. The sideways lash on the rocker arm assembly should be ver small - just enough to squeeze out some oil but maintain free play of the rocket arm.
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Old 15-12-2019, 07:10   #7
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Re: Knew knocking sound after adjusting valves

It's not a knock. Clicking or rattling is more like it. They were off. sound is just new and it caught my attention. On some, Rocker arm never had play. its supposed to be 0.015". thats what i set them at. I watched few videos and it appears clicking is fine while cold and it will go away.
injectors and head gasket new in 2017. i retorqed the head in june 19.
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Old 15-12-2019, 08:21   #8
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Re: Knew knocking sound after adjusting valves

If you know they're all set at .015" now, it seems you may have initially learned the 'wrong' sounds. A little too loose is way better than a little too tight, seems like you're good to go...
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Old 15-12-2019, 08:32   #9
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Re: Knew knocking sound after adjusting valves

I agree. If no unusual smoke or discharge and engine makes normal power, should be good to go. The tappet sound should diminish after warm up.

Valves should have been readjusted when head was torqued. What made you reset valves again?
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Old 15-12-2019, 10:04   #10
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Re: Knew knocking sound after adjusting valves

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Originally Posted by phorvati View Post
It's not a knock. Clicking or rattling is more like it. They were off. sound is just new and it caught my attention. On some, Rocker arm never had play. its supposed to be 0.015". thats what i set them at. I watched few videos and it appears clicking is fine while cold and it will go away.
injectors and head gasket new in 2017. i retorqed the head in june 19.
Are the valves supposed to be adjusted cold/hot. Made a tremendous difference on my Norton.
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Old 15-12-2019, 10:17   #11
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Re: Knew knocking sound after adjusting valves

Most diesel manufacturers give a cold spec but check you workshop manual.
I've never seen enough play in the valve train of a diesel to "pry" anything.
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Old 15-12-2019, 11:36   #12
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Re: Knew knocking sound after adjusting valves

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Originally Posted by phorvati View Post
It's not a knock. Clicking or rattling is more like it. They were off. sound is just new and it caught my attention. On some, Rocker arm never had play. its supposed to be 0.015". thats what i set them at. I watched few videos and it appears clicking is fine while cold and it will go away.
injectors and head gasket new in 2017. i retorqed the head in june 19.
The on-line manual I found says adjust at normal operating temperature.
Did you set cold or hot?

It also says .012" for exhaust. You are probably hearing the extra .003"
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Old 15-12-2019, 12:10   #13
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Re: Knew knocking sound after adjusting valves

I believe you should reread the manual. If you are convinced you did it right forget it, if not re do it. You said 0,015. bcboomer read0,012 on exhaust? Cold or at temp.? No one here it there, pun unintended. One thing I hadn't read, is being damn sure the lobe is at the right place. Best of luck.
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Old 15-12-2019, 12:19   #14
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Re: Knew knocking sound after adjusting valves

Very few operators can listen to and engine and pin-point a tappet related noise unless it is really bad that is why mfg require the adjustment on a fixed event or hour/mile schedule. I have 3 diesel engines that I maintain that have mechanical lifters. An International Harvester German Neuss 179 CI (2.8 ltr), a Detroit Diesel 213 (3.5 ltr) CI 2 stroke, engine and a Cummins 506 CI (8.3 liter) engine. The only one I can hear valve train noise on is the Neuss. The other 2 have so much combustion noise that it muffles out the valve train noise. The valves must be adjusted on the set schedule on all of them. Good news is, except for procedural mistakes that I caused, the slow speed engines are easy on mechanical valve trains.

All I can say is, I feel adjusting the mechanical valve train is an art that needs to be developed with practice.
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Old 15-12-2019, 12:23   #15
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Re: Knew knocking sound after adjusting valves

If you are convinced it sounds different, ( I used to think I heard something different at times but never really knew for sure!) I would redo the valve adjustment. It's easy to get confused on where the engine rotation cycle is sometimes.
I always adjusted my gas engines while idling. But too much oil spraying around with diesels!
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