LS7 Dropped Exhaust Valve

Yikes! I would LOVE a C6Z, however, if I was in the market for one, I would like to have enough in the budget to replace the heads....and add a cam.....and headers......:D
 
That motor is seriously damaged, what a waste.

I liked the comment in the story of warranty refusal on another engine were it was revved to 11K in second gear. That might do some damage as well.
 
I dare say that most of the engine problems were cause by the drivers. Back in the old days, the L78 solid lifter engines were known to drop valves on more than a few occasions. The problem seemed to be lack of valve spring pressure. Just switching to the heavier L88 springs seemed to cure the valve float problem. In those cases, the valve was not keeping up with the rest of the valve train and was actually free falling shut, eventually pounding the keepers through the retainers. Might just be the same problem here when guys try the wild rpm thing. Just a thought. A friend of mine who has raced for years is paranoid about having enough spring pressure for the rpm he intends to turn. He never drops valves.
Read near the bottom of the article. When checking the computer, the DTC misfire code came on at 11,000 rpm, second gear. Missed downshift to second instead of 4th, or worse, forgot to shift to third going up. Whether we will admit it or not, most of us are not that good of drivers and do screw up regularly. That engine must have been screaming.........just before the big bang. Can't blame GM on that one. :(
 
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Keith Tedford said:
I dare say that most of the engine problems were cause by the drivers. Back in the old days, the L78 solid lifter engines were known to drop valves on more than a few occasions. The problem seemed to be lack of valve spring pressure. Just switching to the heavier L88 springs seemed to cure the valve float problem. In those cases, the valve was not keeping up with the rest of the valve train and was actually free falling shut, eventually pounding the keepers through the retainers. Might just be the same problem here when guys try the wild rpm thing. Just a thought. A friend of mine who has raced for years is paranoid about having enough spring pressure for the rpm he intends to turn. He never drops valves.
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I'm sorry. I just can't compute how a driver armed with an accelerator pedal can cause valve train issues unless the engine is over revved.
 
Read to the bottom. The computer stored a misfire at 11,000 rpm. I'm amazed that the bottom end held together. I dare say that most of these dropped valve issues are due to over revving beyond the capability of the valve springs to keep up with the valve action, just like in the old days.
 
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Sorry. I thought that was a general statement made regarding most valve train issues. I caught the 11,000 rpm statement on the referenced failure in the article. My bad...
 
Keith can the same be said of the valve spring failure in the C5 motors? I was under the impression that the springs had a history of breaking even at low RPM's. I have seen pictures of the broken springs that thankfully did not drop the valve into the cylinder.
 
The issue with the C5Z's are the valve springs breaking and I actually haven't heard of it happening too often. The C6Z's have a lot of stories going around about the valve breaking and dropping the head of the valve into the combustion chamber. This is due to improper machining of the valve guides causing excessive stress/wear on the lower part of the valve stem until it fatigues and lets go......from my understanding.
 
Extremely loose valve guides seems to lead to heads broken off of valves on low mileage engines. That's a manufacturing problem. An inordinate number of broken valve springs might indicate poor quality steel in the manufacture of the springs. These are high performance cars after all, that will be "tested" by their owners and should be built accordingly. 11,000 rpm indicates that someone should be riding a bicycle or safer still, walking.
 
Keith, maybe the 11,000 rpm was caused by that "skip shift" system. :rofl:
 
Over the years, I've ridden with some people who should stick to automatics. Trying to co-ordinate both hands and both feet is just something that they can not figure out. We all need a rev limiter but some need on a LOT more than others. If these newer Corvettes don't have a rev limiter built in, then GM should consider one. They may be speed limited to the rating of the tires that GM installs but I'm not sure on that. A friend of mine grenaded a clutch disc when down shifting and somehow ended up shifting to low instead of second. The disc blew instantly before he even engaged the clutch. Better that than the pressure plate. Skip shift going down is bad too. :)
 
Would Like To Know What Type Of Mileage Did They Have

What type of mileage did they have on their Corvettes ....
When they started to experience their engine problems ....
 
I've read as low as 12K miles for the ones with the excessively loose valve guides. I can see that being a factory problem. I dare say that most of the rest were due to driver error just like in the old days. Stick to the factory red line or add a rev limiter if you can't handle a car with that kind of horsepower. Even with our musclecars that we had and our 400 hp Vette, things happen pretty quickly. Add another 100 or more horsepower and no experience behind the wheel and bad things happen.
 
my son bought an 06 z06 last fall, he has been in contact with Manny and is working on getting his head replaced. biggest drawback for Ryan is that he lives in Calgary.
 
bigneez said:
my son bought an 06 z06 last fall, he has been in contact with Manny and is working on getting his head replaced. biggest drawback for Ryan is that he lives in Calgary.
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We sure are , got a trick set of our Dasiva Motorsports LS7 heads coming Ryan's way :canada:
 

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