81c3 wrote:
LS6 engines do tend to suck oil into the intake via the crankcase breathing set-up. The telltale side effect is many tiny black dots (oil specks) on the rear facia. The common fix to this is to add an "oil catch can" Several companies make them for around $100. I had installed one on my 02Z and it collected the oil perfectly. At each oil change, it gathered about 3 tablespoon fulls. That doesnt seem like alot, but at least its not going into the intake anymore & the black dots.....gone!

Now see what Gen 3 engines are on this GM document. Hummm not just the '01 LS6. Interesting. But yet the LS6 is the infamous oil 'burner'.

It all started with the 5300 mid sized utility block that the Gen3 is based. The cylinders on the 5300 are siamesed with a small 20mm slot at the top of the cylinders so the coolant passes thru. As the engine temp rises ( generally on the C5 manual transmission models, where aggressive driving is the norm) this area of cooling has a history of distorting the diameter of the cylinder bores due to 'hot spots'. Cylinder bores did not have a consistant temperature.

Add to this that the machining tolerances were to great for both cylinder diameter and cylinder bore taper. The 1999 LS1 OEM rings are thin and ring tension is less than previous engines to reduce friction. The rings could not always seal off the cylinder ( particulary with the manual transmission when a high engine speed an low MAP (absolute manifold pressure) condition occured ( cruising in second gear thru town and not shift up to third, ect). Rings may not '"flutter " but its difficult to seal under those conditions.

The PCV system design contributed to the blow-by issue as the crankcase oil/moisture gases exited thru the valve cover and returned thru the throttle body.

But try as they may the GMPT engineers could not place the cause of this excess oil consumption .

Now come the 2001 LS6 in the Z06. A factory race car. Again with the 5300 block and now ith even more HP features including 1.5mm piston rings with 9 pounds of ring tension. Add the previous Gen 3 issues and Z06 aggressive style drivers and blow by was evident in a higher % ( greater % but less number of engines as the LS1) than GM was "comfortable" with. Even with the relocation of the PCV crankcase oil baffle/ separator under the manifold valley cover .

The LS6es extremes ( higher operating RPM) ,thin , low tension piston rings made it evident to the GMPT engineers at last what the causes of the GEN 3 blow by were. So with the LS6 as the model , GMPT did a band aid fix with the replacement of the second piston ring with an aggressive Napier scarper ring face and increased ring tension from 9 to 13 pounds. ( GMPT said that no hp was lost by the 'fix'). This what was done under #894549. GM handed the qualify of this band-aid to the dealers ( whole story in its self).

The new Napier ring pak did not go into production LS1 or LS6es till the next production year 2002 M/Y for the LS6 and a few weeks later into the 2002 M/Y production LS1 engines. NO REVISED RINGS WENT INTO ANY 2001 M/Y PRODUCTION LINE ENGINE. PERIOD !!!( John Juriga , Assistant Chief engineer for GEN 3 engines) This is all documented. The only revised rings went into owners cars under warranty that qualified as excessive oil consumption under dealer program.

FYI: in mid April 2001 a new piston was introduced to the production line engines ( both LS1 and LS6) under the issue of cold start piston slap complaints by previous year owners. This piston was larger in diameter so as to lessen the dimension between the piston and cylnder bore wall. The new piston also had a new polymer anti friction coating on the piston skirt ( a first for GM engines).

Since the GMPT engineers discovered the cause and the conditions that
'enhanced ' the oil blow by issue , GM told their C5 car owners to drive a little more conservatively i.e. shift sooner, drive not so aggressively and their oil issues would be greatly reduced . According to GM , that helped many owners bring oil blow by within reason. The C5 automatic transmission cars had the least complaints.

Look at the changes to the GEN 4 LS2 engine; coolant passages were changed, machining tolerances were tightened so as to produce a consistant cylinder diameter /taper and tmperature. The LS 2 piston rings use the same aggresive Napier scraper face but they are thinner (1.2mm) than the LS6es (1.5mm) and the combined piston ring tension on the LS2 is less than that of the '01 OEM LS6 (9 pounds).

The PCV system was again addressed on the GEN 4 LS2 with two redesigned crankcase oil baffles /oil separators . Plus two were incorporated, one on the inlet and one on the outlet. The location of the outlet oil separator is still under the valley cover as on the LS6.

Read anywhere , even the C6 Ls2 there are still complaints , granted far less about oil blow by.

Side note ; oil passing thru the combustion chambers is not good and over time and depending on just how much oil passes it will effect horse power as oil will mess up the air /fuel mixture ratio. Oil will foul O2 sensors, shorten the life of the Cats. Burned oil becomes carbon that builds on all surfaces of the piston , the ring lands, cylinder head, valves, ect.

FYI , my 2001 Z06 (prodcution date June 18th) 2001M/Y ended June 21st 2001

The information resources are Dave Hill , Chief Engineer . John Juriga Assistant Chief Engineer for GEN 3 passenger car engines, Jordan Lee GMPT engineer Gen 4 , Mark Damico GMPT Staff engineer.

SpectatorRacing wrote:
The LS6 is damn near bulletproof on the track.

Most guys still run stock motors, as the HP fits perfectly into the NASA "A" class.

Lots of 'em don't even run the catch cans.

The LS2/3 motors are a completely different story.

88BlackZ51 wrote:


why are the LS2/LS3 a diff story?

I'm not an engine guy so I don't know all the issues with the LS2 and 3 internally, but I do know they load up the Right side head full of oil and a bunch of it gets puked into the intake. The oil simply doesn't drain down enough to feed the oil pickup tube. This has the biggest effect/affect on left turns.

The other big problem they saw especially with the LS3 is blow-by. The explosion within the cylinder literally passes by the rings and superheats the oil causing those ultra high oil temps. We saw over 330 even with a cooler. GM came up with a stacked cooler in series that kept it below 300. Without a dry sump, you'll most likely have do some type of cooler stacking to keep the temps below 300. If you have an LS3 and haven't seen those temps yet, it's because you aren't driving hard enough. It will get there!