Piston slap LS3 - this is very interesting

[Merv53]

I would like to know what percentage of ls3 ss owners are effected by piston slap but I guess that we will never know that.
Would it be fair to say that less ls3 owners are effected than aren't. I am one that hasn't experienced the problem but I have only done 35000kms and that could change I guess.

 

[Skylarking]

^ JC members likely have enough mechanical knowledge to actually notice slight piston slap but not all of them consider piston slap to be a substantial issue

On the flip side, Joe Average likely considers cars to be appliances and likely knows little to nothing about mechanical issues. For such mechanically tone deaf owners amongst us, piston slap along with a V8 exhaust burble may just be what V8’s do And it’s not as if a dealer will highlight such piston slap or other warrantable issues to Joe Average when he takes it in for its service though it seems they always point out when brakes and tyres need doing

To me the ‘Joe Average syndrome’ hints at the fact there are likely more problem engines out on the streets than even GM may be aware of or want to admit to itself, those engines not having been reported as noisey bucket of bolts that they actually are.

 

[Skylarking]

Isn't this issue to do with the hot and cold on the aluminium engines? The engine warms up and the piston expands. The noise goes away. Do not rev this engines when cold. The piston is a lot more oval while cold which causes it to slap lol

Yeah, maybe, but I’ve also read it could be tune related. It’s probably a combination of tune, design and very much poor QC during manufacture.

For me, it would have made sense for GM/H to include engine oil temperature and other gauge options within an app that can display them on the MyLink screen. All the GM-LAN infrastructure and data is there so it’s a relatively simple and cheap app that GM/H could have added for the benefit of their enthusiast owners.

Providing such a simple feature along with a recommendation to warm things up before spirited driving would go some way to mitigate long term damage.

And what ever happened to the MyLink App Store that GM initially spruiked back when this system was first released

 

[Calaber]

I'm not referring purely to the fact that the problem is piston slap alone. I had in mind the engines with both the slap and poor tolerances, ie the "dud" engines. It doesn't seem to be a minor issue, as this forum highlights, though naturally, the guys on this forum are enthusiasts and the unwanted noise is a problem for some.
So, what about the Stateside enthusiasts? Surely many more of them must have experienced these problems, is it of concern to them the way it is here? Sure, the Noddys wouldn't notice or care but I find it hard to believe that US enthusiasts dont experience the issue or don't care if they do.

 

[Ron Burgundy]

Yeah, maybe, but I’ve also read it could be tune related. It’s probably a combination of tune, design and very much poor QC during manufacture.

For me, it would have made sense for GM/H to include engine oil temperature and other gauge options within an app that can display them on the MyLink screen. All the GM-LAN infrastructure and data is there so it’s a relatively simple and cheap app that GM/H could have added for the benefit of their enthusiast owners.

Providing such a simple feature along with a recommendation to warm things up before spirited driving would go some way to mitigate long term damage.

And what ever happened to the MyLink App Store that GM initially spruiked back when this system was first released

If it was tune related my second engine would make similar noise as the first one. It does not.

 

[Skylarking]

If it was tune related my second engine would make similar noise as the first one. It does not.

Tune and design would be minor contributors to piston slap, when an engine is cold, but QC is the primary factor which is why I also said “very much poor QC during manufacture”.

But in no way am I trying to diminish the issue... it’s a stuff up by GM design, a bigger stuff up in GM manufacture QC but also a stuff up by Holden input QC and in using these poorly constructed engines...

 

[Ron Burgundy]

Tune and design would be minor contributors to piston slap, when an engine is cold, but QC is the primary factor which is why I also said “very much poor QC during manufacture”.

But in no way am I trying to diminish the issue... it’s a stuff up by GM design, a bigger stuff up in GM manufacture QC but also a stuff up by Holden input QC and in using these poorly constructed engines...

Yep... mass production does not leave room for matching pistons to the block individually.
They build thousands of each within spec, but **** hits the fan for instance when bore is max allowable tollerance size and piston min allowable size...
That's where you get slappety slap slap cacophony.....

 

[07GTS]

all this talk on piston slap and im using forged 2618 alloy pistons in my new build... hmmm....

 

[Skylarking]

Yep... mass production does not leave room for matching pistons to the block individually.
They build thousands of each within spec, but **** hits the fan for instance when bore is max allowable tollerance size and piston min allowable size...
That's where you get slappety slap slap cacophony.....

Yes it does, sort of.
Simply halve the current tolerance so that when two parts at either end of the tolerance extreme are assembled they won’t be as sloppy as having wider tolerances... but that’s expensive and may even not be possible (maybe due to needing some bore to piston clearance).

The other approach is to batch them into different tighter tolerance groupings (pistons and blocks) so wider pistons go into blocks with wider holes with a much closer to spec bore to piston clearance

As I understand the later is easier and cheaper than the former but still more expensive than poor QC and simply not giving a ****

 

[VS 5.0]

I don't recall piston slap ever being an issue with iron lions....is that coz iron or coz Holden did a better job than GM ?