Cold start rattle on LS3 - piston slap :) Engine replaced

[Immortality]

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Stock GM engines are well known to breathe heavy and put lots of oil through the intake, I wonder what causes that? Worst part is it's not a problem restricted to the V8 engine either as the V6's are just as bad.
Poor oil / air separation (PCV) I think.

In regard to the V6, I believe the right bank PCV is very small and worthwhile modifying it larger.

Yeah it seems GM has changed the PCV/breathers for the later V6's. TBH the only real solution is to fit a catch can and stop that oil recirculating back into the intake and burning. Can't be good for emissions right?

 

[Ron Burgundy]

Yeah it seems GM has changed the PCV/breathers for the later V6's. TBH the only real solution is to fit a catch can and stop that oil recirculating back into the intake and burning. Can't be good for emissions right?

Any legality issues with catch cans ?

 

[lmoengnr]

Any legality issues with catch cans ?

As long as they don't vent to atmosphere, they are fine.

 

[RTSV6UTE]

Today I ended up consulting Sonny from Autowerks....and for those who are not familiar, he is one of the best and most reputable engine builders and tuners in NSW.

Hi

I wanted to shift to NSW just so I could get my cars modified and serviced by this guy. I have known him back in the days before Autowerks.

Regards,

RTSV6UTE

 

[Ron Burgundy]

Nice result with cai and tune

 

[VCoz]

I understand the frustration - as explained my LS3 makes the 'noise' when 'cold and under load'. Maybe we need to find a proven solution, without any conflicts of interest and an answer that doesn't have other negative effects - importantly won't impact on our remaining warranty.
The US related forums have debated and had years of experience with these engines and also repeatedly covered this topic yet I haven't found evidence of poor longevity re many LS3 engines driven 'normally'. Certainly those concerned raise valid concerns about the noise - but until its determined from internal inspection that damage is being done through normal driving (expected if driving hard when cold), excessive oil consumption is occurring (correct oil used), factory tune (tuning not altered to richen too much), 95 or 98 fuel (not fuel detonation); otherwise what can we do? I'm not a motor engineer but do we worry ourselves to death or wait and see if anything gets worse while under warranty (what I regularly found on forums is that the noise is there from new and doesn't get worse or cause damage). Maybe someone can find the informed answers needed in the US sites and post it. Until then (link I found on a US site):

 

[Ron Burgundy]

I understand the frustration - as explained my LS3 makes the 'noise' when 'cold and under load'. Maybe we need to find a proven solution, without any conflicts of interest and an answer that doesn't have other negative effects - importantly won't impact on our remaining warranty.
The US related forums have debated and had years of experience with these engines and also repeatedly covered this topic yet I haven't found evidence of poor longevity re many LS3 engines driven 'normally'. Certainly those concerned raise valid concerns about the noise - but until its determined from internal inspection that damage is being done through normal driving (expected if driving hard when cold), excessive oil consumption is occurring (correct oil used), factory tune (tuning not altered to richen too much), 95 or 98 fuel (not fuel detonation); otherwise what can we do? I'm not a motor engineer but do we worry ourselves to death or wait and see if anything gets worse while under warranty (what I regularly found on forums is that the noise is there from new and doesn't get worse or cause damage). Maybe someone can find the informed answers needed in the US sites and post it. Until then (link I found on a US site):

You are spot on mate
To me .. monstar theory makes sense and I will let it go...

 

[blackve76]

Bloody odd as my Jan 16 build is nice and quiet in the garage with headers etc when cold, maybe a bad batch has gone through with excessive bore clerence.

 

[Ron Burgundy]

Bloody odd as my Jan 16 build is nice and quiet in the garage with headers etc when cold, maybe a bad batch has gone through with excessive bore clerence.

Very very unlikely plus in my case it does not explain the scenario

 

[VCoz]

Ron above you raised the Catch Can topic: here is a link (to the US SS forum) which you may be interested in (remembering in this topic and the 'piston slap' concern you have the Ls3 engine not a Ls2 or Ls1 which should be considered differently). If I still had a 3.6 SIDI I would get a Catch Can due to the reported carbonizing at the valve stems (as no petrol flushing in SIDI) but have for myself decided not needed for my Ls3. Member nothingtosehere SS Forum (Senior Member) provided the interesting graph copied below.
http://www.ssforums.com/forum/engine-technical-discussion/78857-become-oil-catch-can-believer.html

The link also shows the time driven this way/ambient temps for engine oil and water temp rises in that Ls3 (driven as shown by the average rpm blue line) which may also explain the 'cold loaded noise' duration some hear and others don't hear (my average rpm cold when I hear the 'noise' under load would be far less (under 2000rpm)) - one site suggested high idle speed for a short time helps reduce cold piston slap (I found a short idle before driving off helps). I assume your Ls3, like mine, is quiet at idle (cold or hot) and you hear no 'noise' when driven (variable rpm) at operating temperature. Thought this graph was worth raising.