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Old 05-02-2011, 03:59 PM   #1
slipryvette
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Default engine knock in 2008 LS3

Has anyone been succesful in getting a chevy dealer to repair a bad engine slap, or piston slap? This happens when cold start for a period, sounds like a cummins with a load knock. HELP
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Old 05-02-2011, 04:56 PM   #2
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Ahhhhh, maybe you'd do better in the C6 section of this forum
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Old 05-02-2011, 05:40 PM   #3
Z06X
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Ehhh...C6/C5...what's the difference.

I can say one thing, my car slaps like hell and I hate it. I've had many built motors in my life and they didn't even slap like these LSx's do. Once I hit 165 degrees it purrs, but before that it's all clatter. Common problem...what can you do really? It's a well documented issue and really has no ill effects on an engine, you just would preferrably not whip the car cold. I putt around until I hit 155 or so, then start to get moving a little more. I can say though, it's really a quirk of these cars I could do without.
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Old 05-02-2011, 05:48 PM   #4
AU N EGL
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Normal.. Let it warm up for a min or two before you drive off
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Old 05-02-2011, 06:08 PM   #5
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Thanks; I know others share same noise, still runsssssssssss strong.
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Old 05-02-2011, 06:22 PM   #6
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Quote:
Originally Posted by arctic 92 View Post
Ehhh...C6/C5...what's the difference.

I can say one thing, my car slaps like hell and I hate it. I've had many built motors in my life and they didn't even slap like these LSx's do. Once I hit 165 degrees it purrs, but before that it's all clatter. Common problem...what can you do really? It's a well documented issue and really has no ill effects on an engine, you just would preferrably not whip the car cold. I putt around until I hit 155 or so, then start to get moving a little more. I can say though, it's really a quirk of these cars I could do without.
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Old 05-03-2011, 10:09 AM   #7
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Yes, some corvette customers have had success getting GM to replace the pistons...
check piston slap . com
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Old 12-12-2012, 11:14 AM   #8
don22u
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My 2008 LS3. GM replaced the lifters. that didn't work.
GM replaced the camshaft assembly and lifters, removed excessive carbon from pistons, fuel injection bulletin- guess what, the knocking is still there.
A deep knock at start up, engine runs rough, lasts well over a minute; sounds similar to a diesel, so I gotta say, "that aint normal."
GM is looking at it again
My suggestion, Persist. By the way, anyone who says knocking is normal and doesn't degrade are incorrect. If the engines didn't require oil, then no problem, but the knocking is telling you tolerances are off and the banging between surfaces does degrade each, the law of physics and materials tells us that. So, on the immediacy maybe no problem over time come on
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Old 12-12-2012, 01:26 PM   #9
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Anyone have a video of the knocking sound of their engine?
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Old 12-12-2012, 01:44 PM   #10
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Quote:
Originally Posted by slipryvette View Post
Has anyone been succesful in getting a chevy dealer to repair a bad engine slap, or piston slap? This happens when cold start for a period, sounds like a cummins with a load knock. HELP
Depends if youre still under warranty. If not it will cost a fortune for them to even diagnose it. A bottom end knock is not normal at all, especially if it sounds like a diesel. If your warranty expired them I would recommend to find a good shop familiar with LS motors to diagnose it. I would not go to a dealer after warranty. Usually that sound is associated with the rod bearings which are not the greatest oem.
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Old 12-12-2012, 01:46 PM   #11
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Originally Posted by tlove32 View Post
Anyone have a video of the knocking sound of their engine?
Just youtube "ls1 knocking sound", tons of vids.
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Old 12-12-2012, 02:55 PM   #12
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I have audio. I placed a recorder on top of the engine, underneath the engine and in the cabin. Definitely can hear the clang clanging
As I mentioned previously, if under warranty, persist for the tech's will start it the next morning not hear it and say nothing's wrong. My audio's fixed that problem
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Old 12-12-2012, 06:02 PM   #13
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Quote:
Originally Posted by C5Natie View Post
Just youtube "ls1 knocking sound", tons of vids.


I'm aware of what it sounds like, my reason for asking was to determine if it knock is valvetrain related (slow knock) or if it's the bottom end (much faster knock)
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Old 12-12-2012, 06:26 PM   #14
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Very common, my 01 z28 did the same thing. It's all good..
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Old 12-12-2012, 08:07 PM   #15
don22u
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Video won't do you any good. The valve train issue is a tear down of which you will not be able to determine anything by a video. You can change the lifter to ls7 but with the variable timing of the ls3 you're fooling around with kabooms.
I'd suggest you take it to a non dealership corvette shop. That's where the motor heads are that can determine your situation and get er fixed.
GM mechanics are bumper to bumper now. So today he works on a malibu, tomorrow your vette- hey they're all the same, they burn gasonline they say. Don't fool around with it if you don't know what you're doing for a crate is $13500 plus install
Good luck
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Old 12-13-2012, 12:57 AM   #16
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These motors are crazy noisy. Especially if you have a cam swap.
With the C5 cabin literally right behind the engine, we are prone to hear it more than you would in an Fbody.
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Old 12-13-2012, 08:18 AM   #17
don22u
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So what is your point that is helpful. I'm finding these forums are becoming places to.....

By the way, "these motors" are NOT "crazy noisy." They're smooth, fluid power engines through the range. Sounds like you have a diesel and weren't told about it

And as to the cam swap, the lift and rise, the lifters all have a synergy as well; yes they complement each other to deliver fuel and remove fuel remnants and burnt gases. So I don't understand how you can throw a comment out there that by replacing a component of a tested design, that it will be worse than the malfunctioning one that was replaced because it was bad

I'm a bit rankled in that I posted to seek help. What I've gotten is "crying in the beer", complaining and assumptions that do not pass the test of hey that might be a solution. That doesn't solve the comments and neither do yours.

I'd suggest if you're drinking heavily or smoking something you stop. Its messing with the ability to analyze, evaluate and solve
But thanks for responding.
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Old 12-13-2012, 09:39 AM   #18
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The most expensive part of the fix is the gasket set. Go get a price on that, pull the motor, tear it down, pick up a set of pistons, get the thing bored and stick em in. Slap it back together and you're back in business. Gaskets should be about $550, Parts and labor should be next to nothing, pistons and bearings are cheap and so is machine work. Start with a piston that's round and cylindrical, stick it in a hole that's round and cylindrical, and the noise will be gone. There's no easier fix, and it ain't goin away without help.
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Old 12-13-2012, 11:48 AM   #19
C5Natie
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Quote:
Originally Posted by don22u View Post
Video won't do you any good. The valve train issue is a tear down of which you will not be able to determine anything by a video. You can change the lifter to ls7 but with the variable timing of the ls3 you're fooling around with kabooms.
I'd suggest you take it to a non dealership corvette shop. That's where the motor heads are that can determine your situation and get er fixed.
GM mechanics are bumper to bumper now. So today he works on a malibu, tomorrow your vette- hey they're all the same, they burn gasonline they say. Don't fool around with it if you don't know what you're doing for a crate is $13500 plus install
Good luck
Im sorry but the LS3's in Corvettes do not have vvt nor cylinder deactivation. Only the L99 in the Camaro SS auto does and the 6.2L motors in trucks and suv's. My "LS3" block is a L92 that had cylinder deactivation, the 6.2L alu blocks are identical. The right valley cover with the oil passage blockages, a cam swap and LS7 lifters and no more vvt/dod. It runs like a clock, nothing went kaboom.

Last edited by C5Natie; 12-13-2012 at 01:39 PM.
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Old 12-13-2012, 01:59 PM   #20
robert miller
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Quote:
Originally Posted by K-Spaz View Post
The most expensive part of the fix is the gasket set. Go get a price on that, pull the motor, tear it down, pick up a set of pistons, get the thing bored and stick em in. Slap it back together and you're back in business. Gaskets should be about $550, Parts and labor should be next to nothing, pistons and bearings are cheap and so is machine work. Start with a piston that's round and cylindrical, stick it in a hole that's round and cylindrical, and the noise will be gone. There's no easier fix, and it ain't goin away without help.
Just trying to be funny here correct. NOT
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Old 12-13-2012, 01:59 PM
 
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