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LS3 Lifter noise or Piston Slap?

IBLOWN

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shot on a crapple iPhone 13
From dead cold start to warmed and completely gone is almost 5 minutes.
You can hear the knocking more clearly. It really is that loud in person! is this really piston slap or something worse?
The lower pully seems to look a bit wobbly but i don't think that is the cause of the sound as it remains wobbly after engine is warm



Noise disappears at this temp every timeView attachment 238760
Listening with headphones - Its the same knock as mine. Just yours is worse (Sorry). Have you noticed its worse on colder days? I dont even notice mine last summer. Last winter it was bad. Had the lifters done this summer, got the car back and it was fine. Soon as it started getting cold, the noise came back. But its never consitent. You can have a very cold day and its not bad. Same temp day or slightly warmer and its bad. Theres no pattern. My noise isnt consistent.
 

IBLOWN

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Heres some notes ive been taking lately. I just roughly write them down before i forget.

"
-Knocks at idle on cold start
-Different everyday, sometimes good, sometimes bad
-Quiet in summer, bad in winter
-Knock stops when, holding a gear and rolling
-Takes about 10mins to stop knocking while driving
-When first noticed the knock, most of the time it would greatly improve after about 30secs at idle. Now takes 10mins of driving to go away.(Might -be comparing summer to winter though)
-Have replaced lifters with LS7's and Smith Bros Rocker Trunnion Bearing Upgrade (Solid bronze bushes instead of needle roller bearings). Car came back quiet, but i had them done in summer.
-First noticed the noise all of a sudden, didnt used to make the noise
-Oil pressure normal on gauge (300KPA cold at idle, 200KPA hot, pressure rises from there with engine revs)
-Have disconnected one injector at a time - no change in knock sound
-Have pulled off rocker covers, all rocker arms have no up and down movement, only side to side. Have not checked lifter preload properly though.
-Knock seems to be too slow for bottom end, but too fast for valve train?
-Whatever the knock is, its definately ONE component, not multiple.
-Cant hear any difference in loudness from one side of the motor to the other
-Sounds like the sound resonates from the sump? Sounds like about the thickness and volume of aluminium
-Sound is consistent when gently revving when stationary i.e just off idle to 3000rpm (Sound volume doesnt change)
-Its not louder or quieter depending on engine load
-Worse in the morning startup, sometimes just as bad in the afternoon startup, but sometimes nearly silent on afternoon startup even when the weather is very cold (Not consistant)


-Before lifters were replaced (Just coming out of winter/Start of Spring)

-After lifters replaced just as the weather cooled down (2 months after lifters replaced)

Same noise in both videos"
 

VS 5.0

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Has anyone tried using a length of garden hose around various parts of the engine to try and isolate the location of the noise ?

Rembering to avoid any moving parts like pulleys and belts.
 

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Has anyone tried using a length of garden hose around various parts of the engine to try and isolate the location of the noise ?

Rembering to avoid any moving parts like pulleys and belts.
Mate,who needs to buy a stethoscope, nothing wrong with a bit of garden hose and a lot cheaper to. I've even seen people using long screwdrivers, whatever works.
 

IBLOWN

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Has anyone tried using a length of garden hose around various parts of the engine to try and isolate the location of the noise ?

Rembering to avoid any moving parts like pulleys and belts.
Yes, you cant pinpoint the noise. Its the same everywhere you listen. Hard to pinpoint acoustics with aluminium.
 

Skylarking

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I’d guess piston knocks tends to occur at the points where the piston changes direction. If that’s true, then you’d think you’d get two knocks for each crank rotation. So the frequency of any knocking in a piston is dependant on the speed of crank rotation, specifically double the crank angle sensor frequency.

If many pistons are knocking, the frequency increases proportionally in some harmonic fashion…
And the knocks should be heard by placing a sensor (mic or better still a vibration sensor) at the bottom of the block near the bottom of each piston bore. But other things also hammer away within an engine, specifically the pushrods, rockers and valves as well as conrods (at the big and little end) to a less extent. All this can make it had to work out what noise is from where. At least intensity reduces as you move away from the source, so if your sensors are listening low in the block the top end nose should be less, you’d think… And IIRC the cam runs at half the speed of the crank so such should be discernible on test equipment…

The great thing is that Holden has done all the hard work and has all the data about what hammers away at what point in time w.r.t. TDC and in what proportion to speed of crank rotation. They’ve even built a PC based test tool that can measure such noise and use clever analysis to filter away known noise sources. Oddly they don’t ever seem to want to use it for correct diagnosis. It’s even defined within the workshop manual… But supply of that tool may be an issue so dealers use a cheaper tools known as ears (stick on mic) but that require in depth user knowledge and skill to use effectively so stuff just doesn’t get diagnosed correctly which is how I suspect Holden wants it…

Luckily if you have a CRO, it may be possible to work out those noise relationships. I’d try and connect CAS on one trace (to use as a reference) and a mic on another (to pick up knocks) and look at the frequencies and try to correlate it to what’s happening internally. I’d hope the piston knock would stand out more than the other percussive sounds…

Such should provide a bit more than ears on a garden hose but even that’s a good start as compared to a module phone recording.
 

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Have you checked its not a broken valve spring / bent pushrod. Some folk rev the guts out of V8s when theyre in neutral (not under load) cause it sounds cool fact is engines dont like it much and it can munt them.... My ls1 is over 20 years old and id never rev it past 1000rpm not under load ...I drive it slow until it gets up to temp...then the world is your oyster... 20 plus years on and still going strong.... no ticks...no rattles....purrs like the cat it is........lol
The place i took mine to said they checked all that and said there were no problems.
 

Kakodaemon

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Hi mate as to previous, it sounds like ours especially when you let the revs. drop and you get that deeper knocking noise. To give you some idea how difficult it is to evaluate. The bloke from the Automobile Association didn't even pick it up. He reckoned that it was injectors opening and closing. When I took it to the former Holden dealers, l left it there overnight so that they could hear a cold startup. As soon as it fired he put it under load and said piston slap, very common in the full aluminium GM motors. Then he went on to say that ours wasn't to bad and you could hear some of the LS motors a couple of blocks away. The Dealership said that it was within specifications.
That they have given me warranty up to 200,000ks speaks volumes as to the longevity of these engines. Even with the pistons rattling up the bores, it still doesn't burn a drop of oil.
Noticed you are in NZ, maybe the Holden dealers there are more sensible/nicer than here in Oz? :)
Drop mine off Wednesday arvo at Holden for them to look at Thursday, but i doubt I'll get any such special warranty.
 

Kakodaemon

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Listening with headphones - Its the same knock as mine. Just yours is worse (Sorry). Have you noticed its worse on colder days? I dont even notice mine last summer. Last winter it was bad. Had the lifters done this summer, got the car back and it was fine. Soon as it started getting cold, the noise came back. But its never consitent. You can have a very cold day and its not bad. Same temp day or slightly warmer and its bad. Theres no pattern. My noise isnt consistent.
Yeah it got worse/louder the last 3-4 weeks as the cooler weather hit. Mine is completely consistent, same noise right up until the same temperature then trails off and goes away.
 

Kakodaemon

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Yes, you cant pinpoint the noise. Its the same everywhere you listen. Hard to pinpoint acoustics with aluminium.
Exactly. Doesn't matter where you stand the noise seems to sound the same.
Where I live there is a very steep driveway (which i can't drive down) down to the house.
It is basically parallel to my car just a decent 3-4 meteres lower and when i remote start down there the noise seems louder than standing up in front of it, not sure if that indicates that the noise may be lower in the engine bay than higher??
 
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