My friend Jon put this video up on YouTube a few months ago, showing me driving a certain magazine's long-term C7 at Shenandoah from the perspective of his C5 Z06. (A video from my perspective is after the jump.) It's readily apparent from the way it scoots away into the distance just how fast and how pleasant to drive the newest Corvette is. That alone has been enough for me to recommend it over any of Porsche's current offerings, the same way I recommended the C6 Z06 over any of the Porsches available at *that* time. Recently, however, I've been taken to task for wearing rose-colored glasses when it comes to the reliability of the fantastic thermoplastic near-supercar, and I'm afraid my critics have a valid point.
At just six thousand miles, Car and Driver's long-term Vette suffered an engine failure:
an investigation by GM pinned tentative blame on a piece of metal debris (likely from a bad oil filter) that worked its way into the oiling system and wrecked a connecting-rod bearing, which created even more debris that damaged the engine's bottom-end. Given the LT1's tight tolerances and high-performance design, it didn't take much to upset its workings. We've heard of a few similar accounts throughout the Stingray community and GM says it's aware of the issue and is analyzing its manufacturing process for a root cause
Aspiring autojournos could learn a lot from the way in which Mike Sutton manages to praise the LT1 even as he discusses a complete engine failure. Sure makes you paranoid about your oil filter, doesn't it? All of a sudden, the fact that my local Porsche dealer charges $32.90 for a cartridge filter makes sense — or it would make sense if Advance Auto Parts didn't sell the same thing for $5.49, anyway. This would make for a good local news segment. "Are rogue oil filters killing your tight-toleranced, high-performance engine? The Six On Your Side news team finds out."
A website called Corvette C7 Fiasco, run by a fellow who obviously and passionately hates the Corvette, its chief engineer, and General Motors, is tracking a variety of issues with the car, from "illegal wiretapping" courtesy of the Performance Data Recorder option to failures of the engine and torque-tube assembly. The site's owner claims that ten percent or more of C7 Corvettes will eventually fail. He alleges that a second C7 provided to C/D also experienced engine failure during the "Lightning Lap". He blames polymer bearing coatings for failures in the LT1 and LS7 engines.
Long-time TTAC readers will recall that I have beat the drum long and hard about fundamental problems with Porsche's M96 engine as it was installed in the Boxster and 911 from 1997 to 2009. I've gone as far as to suggest that TTACers avoiding joining me in the far-from-exclusive Boxster Owners' Club due to the high percentage of intermediate main shaft failures in these engines, and that they adopt a wait-and-see approach to the all-new, direct-injected engine that replaced the M96. (Would-be buyers of the 996 Turbo and GT3 models, with their "Metzger" engines, have my recommendation, my blessing, and my envy.) I've also suggested that Porsche's handling of the M96 issues has clearly indicated their contempt for the people who purchase their products, particularly those of us who don't always buy our Porsches from a Porsche showroom.
During a discussion on a small Porsche forum last week, another member straight-up challenged me to apply the same kind of critical thinking to the Corvette. "Go back and look at the LT1 failures." When I responded that — unlike Porsche with the M96 — GM was assuming full responsibility and replacing the engines without question, much as Porsche has done more recently with the 991 GT3, he then told me to look into failures of the LS7 and LS6 engines from the previous generations of Z06 Corvette. So I took his advice, and I didn't like what I found.
The LS7 that powers the mighty, high-performance, super-cool C6 Z06 (see what I did there?) is subject to valve guide failure. GM claims that the problem affects a small percentage of LS7s built before Feb 2011, when a new inspection procedure "100% eliminated" the failure. The problem is that this might not be true, with some mechanics reporting heavy valve guide wear on all LS7 engines regardless of age. There's even a suggestion that the faulty head design continues into the Camaro Z/28, which would be a shame.
What about its predecessor, the LS6? Turns out that engine has become Internet famous for dropping valves. The valve spring breaks at the friction valve and, much like Jabba the Hut pressing the button on the Sarlacc Pit's trapdoor, allows the valve to fall into the cylinder, where it has a brief but remarkably intense meeting with a piston. This happens to the first-gen CTS-V as well as to the Z06. In this case, the fix is easier and better-understood than with either the LS7 or LT1 issue — you just go buy some better valve springs. It's a $185 solution, as long as you're comfortable installing your own valve springs. What? You're not? Sissy. Still, if I bought a Z06 it would be the first thing I'd do, and by "do" I mean "have done". Although maybe it's easier to work on the valve springs in a pushrod Chevy than it is to fuss with them in an SOHC Neon.
I should note that Z06es of both generations are neither claimed nor known to be bulletproof on track. The C5 in particular requires additional transmission cooling. Eleven years ago I looked into the idea of using a C5 Z06 as a combination SCCA National Solo/trackday car and although I knew nothing about the dropped-valve issue, I found out that the mods you need to make the car run well on a track take you outside SCCA's Stock class. Which scotched that idea. So I got something reliable that could run in both — a Boxster S.
Yes, you can laugh now.
And this would be a good time to note that, at some point, I put a Porsche Motorsports baffled sump onto the Boxster. Naturally I did not do that while I was running the car in National Solo, because that would have been a violation of the letter if not the spirit of the rules. This would also be a good time to note that installation of that sump did not prevent the Boxster from doing the "DRIVE ME TO WORKSHOP NOWWWWWWW" thing at both Watkins Glen and Summit Point, in high-g loading situations caused by the fitment of Hoosier DOT-R tires.
As a result of looking through all this information, I've come to the conclusion that were I in the market for a new performance car, I would take a wait-and-see approach to C7 ownership. Were I in the market for an LS7 Z06, I'd consider swapping the heads for higher-performance aftermarket re-ports from Lingenfelter or Vengeance or someone else. Were I in the market for an LS6 Z06, I'd swap those valve springs pronto. Only time will tell if the LT1 issue is easily fixable, or whether the Feb-2011 "inspection" from GM really cured the problem in later C6 Z06es, but at least in the latter case there's currently a prophylactic step possible. With the LT1, it's just wait and see until somebody figures out what's really going on. Hint: I doubt it's the oil filter.
Despite all the above, I'd still feel more comfortable buying a Corvette than I would a Porsche, and the reason is simple: GM's doing something. The problem with the M96 fiasco wasn't the IMS or RMS issue itself. Every manufactured good is subject to problems and nobody is perfect. The problem was the attitude that Porsche took toward the problem. They treated customers like enemies, like they were the problem. They denied the issue for years, they did little or nothing to fix it, and they didn't retreat from that stance until their own customers got together to sue them. That sort of mindset is more damaging than any individual manufacturing defect could ever be. I want to believe that the quick action they took regarding the problems with the GT3 is indicative of a change in that mindset, but I fear that had the problem affected all the DI 911s — or if it does affect them all — they'd check their balance sheet long and hard before doing the right thing.
Not that I'd buy either a new Corvette or a new Porsche with my own money. I'd buy a Viper. At eighty-four grand for the recently re-priced base version, it's an outright steal. And the Viper TA continues to be my favorite production automobile. Do Vipers have problems? If they do, as the man once said…
The post No Fixed Abode: Holding Corvette to the same standard. appeared first on The Truth About Cars.
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