Was reading the Car & Driver Lightning lap article and this caught my attention in relation to this thread, "During the development of the LT6, the engine team found hot spots in the main bearings that it attributed to cavitation near redline when the oil thinned out at high temperatures. To combat that, the Z06 nose has a number of heat exchangers that keep oil temps below 200 degrees.". It's probably unrelated to the engine failures but it's interesting nonetheless. Let's hope we eventually get some info from GM (not holding my breath) so we have confidence as we patiently wait for an allocation.

 

Well, on that same note colder oil that has much lower viscosity will have similar problem on those bearings. You dont want the oil to be too hot which thins it out but you also dont want it too cold (especially once the engine has warmed up and everything else expanded) because now your viscosity is again too low (due to different reason). It has to be just right.

 

A humble opinion. Engine misfire signals and resulting codes are generally due to excess fuel at the catalytic converter. Spun or damaged bearings are less likely to produce a condition that would result in engine misfire codes on only one cylinder bank (1,3,5,7). Like the previously reported failure at just over 50 miles, I would suspect a valve train issue effecting fuel distribution on one bank. In the video of the earlier failure you could actually see what appeared to be raw fuel coming out of the right exhaust, and it set misfire codes on one bank as well. I guess a more severe piston failure could also potentially effect fuel distribution, but the video did not sound like that heavy a failure. I'm putting my bet down on valve spring or cam follower failure.

 

GM did plenty, they replaced or repaired every engine that failed during the powertrain warranty period. I personally know of 9 engines that failed at the track or just after the car left the track. One of them was mine, I lost the LS7 in my C6Z while on the track at the Glen. GM replaced the engine under warranty so they did their part just like they did with this person's engine.

As for the LS7 failure myth, there were far more reports of maybe incorrect valve guide clearances and maybe unneeded remedial actions than actual engine failures. Everybody was fixing their engines in an attempt to preempt failure. The problem trying to fix the engine before it broke was what do you fix? Nobody knew for sure why the few failures that occurred had failed. There were assumptions that it was because the sodium-filled hollow stainless exhaust valve broke off, or was it because the valve guide bores weren't centered with the valve seat and that caused the exhaust valve head to eventually break off?

Then we got the wiggle test in an attempt to cheaply diagnose whether or not the valve guide clearance was excessive. The problem was the wiggle test is totally useless of showing anything other than there is some wiggling taking place. The truth is nobody knows the reason why some of the LS7 engines failed but there has been a lot of money spent preempting a failure that may or may not occur. When you look at the total number of LS7 engines that were produced and delivered by GM in the C6 you have a number in the low hundreds out of a total number of 27,995 engines delivered.

Bill

 

... and once out of warranty many of us were not willing to just sit around waiting for an "unexpected" $18K installed repair build with an engine that would have the same problems.

14 valve guides out of spec at 46K miles,

Ti rod rubbing at 57K miles

Two reasonable shots at that $18K replacement, now with an engine that is no longer available.

I was proactive and was able to do many performance events with the mods I did and my LS7 has worked out well for me, but the core problems with the factory LS7 engine was the catalyst.

Dave

 

I literally just watched the video on YouTube. Glad you got it taken care of relatively quick.

 

Good info.

A devout NCCC member (who organized many, many track events) and great driver had 3 blown LS7 engines. The third one was out of his pocket and sold the car, got a GS. I followed the LS7 history (wanted to replace my aging C4 ZR-1) and got gun shy because of the bad publicity. I believe someone documented 0 psi oil pressure during extended, high g left hand turns (like Turn 1 at Pocono). I also believe most street driven LS7 were fine.

 

Let’s not forget the first year C5 z06 LS6 aka the oil burner. Mine never burned a drop of oil but it didn’t matter. The next year the engine was upgraded and they added another 20 HP basically turning the first year model in to an also ran.

It’s fun trying to sell a car and convincing someone it’s not an oil burner.

I also had a problem free C6 z06 but no matter. The LS7 did have issues so when you tried to sell one first thing asked was “ are the heads done ? “. So no you didn’t have to do a preemptive repair but selling it without it was a PITA.

Good luck on this one !

 

The oil pressure loss in high G left turns was in the early LS7s that only had the 8 or 8.5 quart systems. The 2009 and newer cars with the 10.5 quart systems were not known for that problem. Some of us who have the bigger tanks also have done the Aviad oil pan baffle install to reduce the risk further. The problem was extended 1.2+ G left turns and generally required R-compound or racing tires.

 

Not the same thing obviously but I had an s2000 that never saw a day without a ton of redlines, for years and years ... When the engine was definitely not warm. Just saying, that engine ran like new even when I sold it

 

I don't recall the 'test' being repeated with the 'winged' oil tank. The original test showed 0 psi @ 1g on left turns (didn't need Hoosiers). Accelerated valve guide wears were observed even with the larger oil tank equipped cars as well. It was a shame because the LS7 engines were strong. It pulled in 4th gear as hard as my old C4 ZR-1 in 3rd. I hope the LT6 will have a success and won't be plagued like the LS7. In a year or so we'll see it.

 

The more I read about this motor, the more sure I am of getting my car delivered at the museum. I don't want to take a chance for any delivery driver, sales person at dealership(s), etc. giving it some quick revs for their own joy or worse, a quick rip down the road before its up to operating temps.

 

I bet that the LT6 sees close to redline more often then the LT2 does? Every drivers most likely to show off the LT6 symphony at every chance?
I think it will be ok and hope that it won't be like the LS7. It will be a trap for those that buy used with expired warranty or out of production. We will find out in the coming years.

 

For all you know those 1500 miles/year were all on the track. Stay classy.

 

0.3% failure rate would be awesome for an engine that’s been in production for some time, but these are all EARLY LIFE failures. Not good when you extrapolate it out to long term failure rates.

 

Same here!

Although GM has commented that this new Z06 will blow up faster than any other Corvette made. I believe them!

 

^^^ ??? Where was that said? .. and did they mean only because it revs way higher than any previous production engine they have made?

 

This MUST be out of context. No one at GM/Chevrolet would EVER make that statement publicly...

 

It depends on the cause of the failure. Something like an engine is most likely to fail early in its life or when it gets to really high miles. The whole “bathtub curve” for product failure.

I’ll be a lot more concerned if LT6s start regularly crapping out at like 20-50k miles.

 

yes I believe the valve guide wear was a separate issue from the oil starvation. GM fixed the oil starvation issue by increasing oil capacity, and (as stated by them, YMMV) traced the valve guide issue to machining concentrically issue. I know there are reports of failures outside the "machining issue effected" heads, so YMMV on how effective GM's corrective action and containment was.