As a retired GM dealer head tech: (ASE Master w/L1 cert.) 40+ years in the buss. and 30+ in a GM dealer I can honestly tell you that GM is the KING at gaslighting!!! Generally when you call about something that will be VERY COSTLY they start to deflect. It's like the old saying: ( If their lips are moving they are lying) Retired 6 yrs now and don't miss one damn thing about dealing with people like that!!!
That’s a really refreshing take from a GM professional. I was in the car business and lost so much money with the GM 3.6L DOHC 24V V6 timing system. This is very surprising about the LS7 pushrod.
Why as a retired 40 year automotive veteran I always printed the recalls/TSBs, and handed my customers the mechanics notes and any photographs before I sent them to the Dealer. I’d tell them to hold back and just ask. The dealer would always blow smoke up their behinds and my customers would hand them the stuff and ask when the car would be ready. Both GM dealers here hate my guts. 🖕’em! My son broke a ring land on a tuned 30k Ecoboost. The tune Ecoboomed the motor. Ford bought him a new one. COMPLETE motor. Gratis! No charge! GM would have said “No warranty due to aftermarket tune” and sent him packing. 💯 %. Ford bought a 25 year old customer for life that day. He’s about to go buy another Coyote Mustang.
They sure have taking the effort to fix the AFM/DOD lifters too... I have my conspiracy theories that when they took the goverment bailout alot was in that paperwork......
@larrygreen9100 I really am a team player but it's hard to care when no one else does. Wondering how upper management took the 10 cents ignition spring tragedy, "isn't it time for your break Larry?" We avoided the Takata air bag fiasco by one model year. A new shotgun with every purchase right there in the steering wheel!
As a machinist, you just have to understand the materials, it make perfect sense to why this happened, Titanium has a coating over the material when the coating wears off then Titanium will gaul and stick, so if the valve coating is wearing away, then most likely the Connecting Rod Coating is doing the same, Bronze will not gual Titanium Valves, going to a Stainless Steel Valve or a Bronze Valve Guide will prevent this, Its time to start looking at the connecting rods before you have a major failure.
Greetings from New Zealand. Thanks for the video and condolences on the blown motor. I have an '07 Z06 which I purchased 2 1/2 years ago. Went for a test drive with the then owner and I just had to own the car. At the time it had around 27,000 miles on it and in the interim I did some 'due diligence' on the LS7 head issue and negotiated a better purchase price. I sent the car to a performance engine shop for checking. The 'wiggle' test was hopeless, so made the call.... The Intake valve to valve guide clearance was top limit and the exhaust was 50% OVER top limit. In addition, one of the trunnion (rocker) bearings was in the process of collapsing. Thank god we checked it because the wife would NOT have been happy. Because I'm an 'old fart' of 70, and will never drive this to it's potential, we fitted 1/4" longer valve guides (better valve stem support) and stainless valves. Still have the Titanium valves if the next owner wants to retro fit. All the best with the 'fix'.
@@KelMcBeath Hello Kel. Sorry for the long delay. We live in Waihi and don't get up to Auckland very often in the 'Vette. Would be good to catch up though.
@@MotivEngineering LOL if valve drops such an issue why not just replace the heads with better aftermarket ones to prevent this issue in the first place?
Vengeance Corvette in Atlanta had a special running that replaced the heads with stage two cnc ported heads with bronze guides and I chose Manley severe duty stainless valves. I think the total bill was about $3500.00. No matter how many miles you have on an engine, get the heads changed out and be done. Anyone who has driven an LS7 would not be happy with an LS3.
There will not be any contaminates in the oil, these valves fail from the fusion weld of the exhaust valves. The valves in the LS7 are hollow and the actual valve is friction welded to the stem, this is the failure point and there is really no way to predict the failure.
Was wondering if anyone was going to bring this up.. Hollow valves are a trade off.. In the past they simply made the valve, then EDM plunge drilled them and filled them with sodium and plug weld the top end.. Gm tried to get fancy and microweld the shaft. Not the best process for this.
I don't think the Del West intakes are hollow or fusion welded. The hollow stem valves are barely strong enough even when hitting the valve seat evenly but throw in a massively worn guide and the poor valve gets side loaded to the extreme, flexes then snaps the head off. It's always the exhaust valve that drops first. I have measured hollow stem exh valves that looked like the stem almost collapsed into an oval with a relatively intact guide. They are junk!
been in a big name OEM and race automotive engine testing lab and the first engine that blew under my watch, blew a rod out the side from a dropped valve was an LS7 back in 2005.
As a heavy equipment technician for a fleet with a lot of experience analysing oil analysis I can tell you it is one useful diagnostic tool. I've used many oil sample analyses to solidify a diagnosis or even prevent a failure occurring. But with that not every failure is detectable or preventable even with the best of maintenance. Some defects can create stress points that don't show signs until it is absolutely too late. For an example most Symptoms of EGR cooler failures are detectable with an increase of potassium and sodium in engine oils, but I've seen clean oil samples where the cooler suddenly dumps coolant into the engine hydrolocking it. Data is important, but you seem to forget one thing, variables and endless and can change or even hinder data useless.
You are 100% right on. Retired now, at one point in my 44 year career, was the fleet manager for an ambulance company. We were running Ford 7.3L turbo diesels. I had the mechanic do oil sampling every 25,000 miles on 22 ambulances. Never had a lot of problems but we did have a brand new 7.3 develop and odd miss and performed the oil sample and discovered a bad cam with infantile failure due to a surface hardening failure. Warrantly replaced the cam and kit including all pushrods, roller rockers and roller lifters. Problem solved no more issues and SAVED an engine.
I currently own a 2015 Z 28 with 35,000 miles on it and have always debated on this issue I’m gonna pull the trigger and get the heads fixed and of course while it’s open upgrade the cam and have headers and high flow cats install the same time I just think it’s peace of mind the car it’s an absolute joy to drive and I love it.
I certainly don’t fault you for that decision. The “I’m part of the cool LS7 club” is way less cool when I’m standing at the side of the road waiting for a tow truck.
All you gotta do is put 3-4k into it doing a good heads cam package and you don't gotta worry about dropping a 15k dollar engine lol. And you'd be as fast as many ls3 with boost.
Got my C6Z06 LS7 with bad bearings and still ongoing rebuild... Lots of headaches about new bearing clearances and parts that are on backorder by GM though... I'm quite interested about the oncoming project of yours and surprised your Oil analysis did not help spot any problem beforehand.
I'd have to say that I would certainly agree with your reasoning on being comfortable with this engine prior to it's failure. Just goes to show how much of a beating a valve can take when it's in a situation that can lead to failure. I'd put an LS7 back in it, lightly modified in the manner of your choice as compared to what you had.
If I'm buying a fairly low mileage used one from a dealer, you think they'll be willing to lower the price if it has stock heads or they don't care about that? Selling my 14 paxton coyote next week & plan on getting a c6z
It's just my theory, but it's based on an experience I had with an early 5.7 V-8 that suffered from valve guide problems at moderately low mileage (60,000 mi.). The LS-7 came equipped with a lot of performance upgrades, with the exception of one thing, roller tipped rockers. GM made the leap to roller camshafts in the late eighties but neglected the one component that enabled the cam to do it's job without causing damage elsewhere. Roller cams have steep or short duration valve opening event ramps, which accelerate the rockers from static to in motion in fractions of a second. It is my opinion based on my experience that this instantaneous motion causes the rocker to not only push the valve stem downward, but additionally, it tends to pull the valve stem up toward the fulcrum of the rocker due to friction between the rocker and stem end. This creates excessive side loading in the guide, causing premature wear and eventual guide failure. In my case, it showed itself by excessive oil consumption via the guides, but with continued use it possibly could have led to catastrophic failure. It eventually led to a complete engine replacement that GM footed the bill for.
This makes sense. I couldn’t see play between the stem and guide alone causing this. I have an olds 455 that has some really gnarly play in the guides, enough to hear and I regularly rev it over 6k rpm without letting it warm up sometimes. Not that one engine proves anything but it has roller rockers and haven’t had an issue. So I was thinking if any motor was gonna drop a valve from having play in the stem it would be this one 😆 so I’m on board with the side loading idea.
This is a relatively exotic engine, materials wise. I wouldn’t expect it to go 100k mi w/o extra maintenance. The valves are Titanium and need to be monitored for elongation. When lash shows the valve has stretched 0.010”, throw them away and put new in. Don’t expect the Titanium con rods to last forever either.
Yeah, people don't realize that titanium is a wonderful material - about as light as aluminum and strong as steel - but it doesn't last or wear like steel. Titanium engine parts should be checked and replaced regularly as wear items. I'm told they're more prone to metal fatigue, a bit like aluminum.
I have seen Japanese motorcycles get 100k on their titanium valves without issues. They are turning 11000-13000 RPMs, but they also are 4 valve motors. They usually are 31 to 33 mm valves also.
@@cyclonebuzz8172 I’ve seen motorcycles drop a titanium valve at less than 20K miles when just riding along. Kawasaki had a lot of trouble when they first went to titanium valves. I think because they were a two piece valve and the head of the valve would fall off.
As an LS7 owner who was scared to even drive to the grocery store until I got the heads "fixed", thanks for making this. There's a lot of back and forth out there and yeah, a TON of people (including Tadge at one point, I do believe) say as long as you keep it stock, you've got nothing to worry about. Haven't looked at the rest of your channel yet, but looking forward to going through it to see what build you decided on. I'm hoping to see an LSX!
Having a motor let go sucks and I feel for you, but: a Small Block Chevy that makes 500hp and runs for 15 years/70k miles (including track use) is still impressive. Not ideal obviously, but no small feat. I have 30k on my 2007 Z06, stock, bought it a year ago, 4 HPDE days so far. Read all the internet stuff, decided I'm not touching a running motor, fingers crossed. This video is very informative, thank you for posting it.
Adam, I don’t disagree with you at all. You obviously understand my mindset after watching the video. I was nervous to open up something that had been working so well for so long. I certainly hope that you have better luck than I did. Keep an eye on it, I’ll be crossing my fingers for you too! -Mike
A heads and cam package would do wonders for piece of mind. That’s what you tell your old lady anyway. I lost my stock motor to ring butting under boost. Still faster than a lot of cars on only 7 1/2 cylinders though. Shockingly seafoam didn’t bring back my compression🤷♂️
Can't agree that it's impressive, 7.0L engine with 500hp, 5.5 mercedes, m113k will do over 500k ? How come all the previous ls engines lasted so much longer ? I would be pissed if my hypothetical corvette blew up at 70k
The head Corvette tech at GM said the valve drop issue occured only on a small handful of engines first produced in 2006. The problem does not exist in 2007-2013. Internet folklore.
Hey man, I don’t think you’d see anything in the oil at all before this failure as it’s not a progressive failure. Most likely the valve stem’s non-conformance to the design tolerances caused the valve head to be subjected to a small elastic strain every time it closed as the head was closing on one side of the seat first. This would cause high cycle fatigue in the neck of the valve, causing an almost instantaneous failure as it finally fractures.
In the preview picture, the intake valves look sunken in the combustion chamber. This type of drop can also be caused by recession. This can be detected before failure. There are wear particles but those get blown out the exhaust. Instead, recession can be tracked by measuring valve protrusion. Intake valve recession is often caused by running aftermarket air filters that pass dirt.
Based on the known probability of occurrence of the failure event described. I suppose a new owner of a used LS7 should simply weigh whether setting a corrected set of heads on the short block, or simply driving it as is.
If you have a LS7, do the upgrades to fix any potential issues. As far as what engine to replace it with depends on what you mainly use the car for. Sounds like you love track. So go with what you is best for you.
The problem is, there is no "THE" upgrades. There are all kinds of theory on why the valves fail. SIde load on the valve, valve material, valve guide material.... No one seems to metion valve springs - but I can tell you a bad valve spring can break a valve (side load placed on valve).
@@confuse9 Agreed. Bad valve springs can cause issues. But the LS 7 is a new animal. It has problems that go beyond valve springs. It's a great and powerful motor, and would to love one! But these motors experience problems way before they should!
This is a fantastic video. I made one on my channel a while back outlining the issue and offering a clear warning and suggestions. Many people criticized that warning and called me every name in the book except for "logical". I have no interest on rolling the dice...I got mine fixed and made the odds a bit better for my Z06...which I truly love.
From what I learned. The centerline of the guide and the centerline of the valve seat are not in line. A brand new head was measured before being installed, and that is where this conclusion came from. The bare head was a replacement under warranty, and the associated parts were loose. The machine shop had a pristine head to check tolerances and found things out of alignment. 2007 Z06, heads fixed, and Crower shaft rockers installed.
Asked my warranty carrier if they would approve a pre-emptive repair and they said no. They wound up paying a 23,000.00 claim. Then we started with a new 5.3 truck block, installed darton dry sleeves, properly machined and ported LS-7 heads, etc.,etc. Now I have a 440 c.i. beast that is awesome to drive on our local road courses. Many thanks to LME!
This sounds oh so familiar. My LT4 is heavily modified, I had a water pump failure and couldn't pull over immediately, by the time I did. I had already done crazy damage. The heads had been redone with .660 springs, trunion upgrades, etc. Typical mods with a cam. Pulled valve covers, found #7 cylinder with spring still compressed, valve was missing, had the block re-sleeved, new forged rods and pistons, 3 days after getting the car back, it dropped #6 valve and beat up #6 forged piston. Found out the springs were re-used in the new heads. The shop is now rebuilding it , at their expense!!! But I don't have much trust in it at this point. My faith in my machine has seriously been disturbed, at this point im just hoping it holds together. The fast car effort is seriously overrated in my mind, at least until I can gap somebody and put it back into perspective.
We had a c6 zo6 at the shop about a year ago, the way the engine failed seemed to be similar. Total destruction, you could look through one side of the block through the other, it had holes on both sides. The only mods were an intake manifold and exhaust
Yea with their modified cars this car is hand built with precision the LS7 does not respond well with modifications a totally bone-stock LS7 engine very seldom any problems.
How do you know they were stock. 2008 through 11 had a small issue and the internet blows it up like they would exaggerate the bottom line when you modify these cars that's when you fall into problems especially the C6 Z06 it's a hand-built specialty engine that does not respond well to modifications.
Because they modify them. The C6 Z06 does not respond well to modifications that engine is hand belt and precision for stock configurations when you listen to the Corvette forum they don't know shit the people think they know it all one person modified their car it blows up and you'd swear a million cars all ZO6 cars have the same problem it's bullshit.
Had this happen 2 years ago after a cam upgrade, the car ran fantastic at the dyno, after i got home and took it back out. Around 2nd or 3rd gear spirited run it just did a quick pop and smoke from the engine. About 8months later, new build : ls3 block bored out with darton sleeves, larger forged pistons, step up larger bore, replaced the one broken titanium rod, everything was fine, kept all the ls7 components ( rotating assembly etc). New set of stock ls7 heads got the entire vlave job completed, kept the titanium valves, upgraded the exhaust to ferrea ss. Tsp stage 2 cam Rocker bushing upgrades Msd intake.manifold Nick Williams TB Basically all bolt ons with extra major internal upgrades, ran 630whp at the dyno and revs to about 7500rpm. Next upgrade will be Vengeance Performance head work, upgrade fuel injectors, and id say gra few extra HP with harmonic balancer and a ported msd intake manifold. I should be able to get this monster to 670whp NA on 91 octane At the most maybe ij the future a procharger running 3lbs for thst extra 50-80hp lol not sure i can get anymore power NA after the heads / msd porting
It seems to me that you have direct evidence from Blackstone that this wasn't a wear issue. Or at least, the amount of wear that occurred prior to failure was slow and steady enough that it didn't show up as abnormal. This was my biggest fear that prevented me from buying a C6 Z06 - the valve issue is not wear related. It may be a problem with the design where the components can be within the manufacturing specs and still have insufficient strength to stay together over time. Fatigue failure rather than wear failure. And my research indicated that some of the aftermarket fixes might not be reliable either. Failure can happen at any time and there's no perfectly reliable indicator. This is similar to why I sold my GT350. I know some owners never have a problem, but the risk wasn't worth it to me. I would consider an LS3 or some other version of the LS as a replacement to avoid recurrence.
Valve failure will never show up in the oil. I’m pretty positive the ls7 have hollow stemmed valves. They are super light weight, but in return they tend to be brittle and unable to stretch, so there is no wear evidence, they just snap eventually.
It's so easy to fix just put a good set of heads on it with stainless valves. Heads cam should be the first thing any ls7 owner does. Why not? You make the car sound wicked and run way better and eliminate this issue all at the same time.
@@midnight347 only thing is, stainless valves weigh more, and valve float is a very bad thing. Make sure you have the proper springs to control those heavier valves. Or go sodium filled very pricey
I bought a Grand Sport for 2 reasons, 1st was the removable top 2nd was the valve drop issues, I did want a Z06 and almost pulled the trigger on one but honestly the valve drop issues is something I could never be comfortable with driving the car wondering if the damn engine is going to blow up every time I run it hard.
Bought the same car, for the same reasons. Gonna be adding AP Radi-cal brakes and a race seat/harness for this upcoming track season, which I'd rather be doing than replacing an engine. Sorry to hear this news, and I wish GM would admit real numbers on these problems, but alas we all seem to get black balled when it's brought up.
C6Z owner (it's been my daily for years). I knew the risk when I bought it. I considered the GS or a ZR1, but I got a GREAT deal on the C6Z and also had to have that 427! Even if it nuked tomorrow, I wouldn't regret the purchase. With that said, I will be doing aftermarket heads, cam, headers, MSD intake, and TB soon. Partly for piece of mind, but mostly for the additional 175-200hp. I have an LS3 in the car in this avatar and it's a great engine (and handles boost better than the LS7), but the higher revving LS7 with it's larger displacement really has my heart. BTW, does the C6 GS have the aluminum frame like the Z06, or is it steel? What about the CF/balsa floors?
Yeah those hollow ferrea valves are drilled out from solid. I think hollow ss intake and solid ss exhaust is the way to go for reliability. Also roller rockers. TFS has the best flowing small runner aftermarket ls7 heads, add yella terra rockers and hollow intake it will be ready for anything. Mamo motorsports builds on this setup, that's my route.
I’m glad I picked up a ls7 bare block for my chevelle and built it from ground up with brodix br7 sts heads with bronze guides and SS valves! The dropped valve shit sounds stressful!
My Corvette specialist said if you're at nearly 50k miles, your chances are lower, but not 0%. They said if you plan to track the car, you should do the heads anyway.
I bought a 8,500 mile Z and the first thing I did was fix the problem via Lingenfelter performance. If you buy the car understand this is not an option. And honestly it’s a great first mod. Gives you a chance to upgrade the valve train , new head gaskets and CNC port the heads. My car makes 531 with no cam , just fixed heads and intake.
Mine had connecting rods rubbing. Found that with an oil sample and then an in-depth look at the oil filter media. My car had the heads “fixed” by lingenfelter when I bought it. I asked the shop to check the heads while the engine was out. Valve guide to stem wear was excessive. Lingenfelter will not stand behind their work nor would I trust them to “fix” their mistake anyway. The exhaust valve seats were already leaking too. Heads are being sent to AI in charlotte NC. Block is being fitted with Eagle forged crank, K1 conn rods, Carrillo pistons BTR stage 3 cam, new lifters, trays, &pushrods. Doing the CHE trunion upgrade to the rocker arms, Manley stainless steel exhaust valves, AI bronze guides (maybe new intake valves too). Kooks 1 7/8, 3”x pipe and McLeod clutch with bleeder. That oughtta fix it lol
My c6z got 85k miles on the clock, the oil sample looks clean and I was thinking the same... If it will drop it should have already been dropped.😢 Damn now I'll get my h/c done sooner
I rebuilt an LT1 from 1996 replace rebuilt everything except pistons. I put 3500 miles on it over three years with no issues. It dropped a valve on start up one day. I drove it home. Still had oil pressure to the upper part of the engine. Pulled it apart, piston was dented but not bad, had the head fixed, new valve, new guide, cleaned up surfaces and reassembled it. Started it up and had no oil pressure to the top end. You may never know what happened to cause the valve to drop. Seems odd it dropped after all that time, but no matter the milage, running any engine hard calls for routine checks / inspections. Hope you can figure out that happened, so you can avoid the issue in the future.
At 50K miles I dropped off my ZO6 with Katech in Detroit for a Stage 2 upgrade. I don't track the car, just some spirited street pulls from time to time. I'm at 70K now and my ZO6 is still running great. Fingers crossed the work Katech did while rebuilding the heads will ward off the dreaded valve drop.
LS3's can't handle more ghan 625 wheel if longevity and reliability is your brew of taste. I know many guys on their 2nd and 3rd LS3, supercharged and right around 615 -630 wheel. None of them have a gm V8 anymore.
The LS7 was also noted for breaking valve springs, which allowed the valve to contact the piston. My neighbour's '06 developed a miss, luckily at slow speed a couple of blocks from home. Fortunately, the spring still kept the valve away from the piston. I replaced the broken spring with the head on the engine after a leakdown test verified the valve wasn't bent and it has worked fine for 5 years now. I did recommend replacing all of the springs, but he is cheap. lol
You could always check the valves by taking the valve covers off and wiggling the valves. Also its super easy to just get new valve guides installed. Also its shitty how GM never truly took care of this issue in their best corvette ever made.
Really love how your channel is narrated and documented. As someone that has worked on a few of these cars (c6zs specifically). They are insanely phenomenal cars that respond well to a cam and ported heads. I would do another stock short block or something similar as they are hard to come by and have the heads repaired and ported. BES Racing engines in ST Leon, Indiana has an amazing LS7 program that is world renowned
I have a 12K LS7 and I'm terrified of what happened to you. I literally have one of the first sold 06 Z06 engines. I don't intend to ever beat on this at all but still keeps me up at night. Peace.
Short answer is NO! IF SS would take the heat & abuse the Ti valves withstand, all serious race engines would run them because they cost 1/10 the price of Ti valves. Weight is another consideration. The lighter the valve train(including lifters, pushrods, rocker arms, valves & retainers), the less the valve spring pressure required to control it. 10,500 RPM NHRA Pro Stock engines run 600+lb SEAT PRESSURE & crazy high open pressure to control big titanium valves without issue. The current method used in race engines of adjusting "installed spring height" is using the peak lift spring pressure rather than seat pressure.
GMs had the wiggle test for YEARS in the 80s/90s it was common for GM calling for "wiggle test" while diagnosing electrical problems , wiggling the entire harness from from to back to see if a fault spike occurs.
If you have an ls7 car don’t risk it you have a couple options you can send the heads out for a professional valve job, or buy an aftermarket set cnc ported heads, you could also send your heads to Texas speed or other head porting services to get a cnc port job and a good valve job, ls7 will make 70-100 hp more with just ported heads and a cam
Coyote swap 😂 sorry I’m a Ford guy and I had to do it. The first motor I ever blew up was a “built” 3 valve that was pro charged after a month of ownership. It lasted 4 years and after I tore it apart I found out the shop that “built” the engine just pocketed my money and threw trash parts into my engine. Lesson learned 👍
So sorry, saw your post on the forum. FWIW, I bought my Z06 with only 6k miles…and the AHP pkg 4 heads actually arrived a day before my car arrived. Just sayin. Turned out several valves were at, or slightly outside GM spec (and way outside AHP spec). Would it have held? How long? Who knows? Too expensive to chance it. And yes…chance of failure obviously increases exponentially with aftermarket cams. Heck…the engine already has 1.8:1 rocker ratio. I’ll also add that with such oil temps, I use heavier oil, moreover with much higher ZDDP for added lubricity. And try to keep oil under 250f (long story). Again, sorry for your failure. I’d source another LS7 (stock cam!) and make sure the heads are refurbished. Good luck…and great video
This is where good quality machine work is worth it’s weight in gold, but good chance valve spring fatigue/lack of spring rate is the cause of this, and most certainly not oil contamination
Thanks for sharing. I owned a C6Z for a couple years. I miss how special that car was, but not the interior. With the valve issue, driving that car was like dating a stripper. Amazing and insane, but in the back of your mind you always had to be aware it could go very wrong, without warning, at any time.
That's why before I put my Ls7 back in my c6, I replaced the valves, the keepers, rockers, springs, and valve guides..... Haven't had any problems whatsoever. (Then again I didn't have any to begin with but did it anyways) And BTW, I've seen the valve drop at low miles and high miles....it doesn't matter until it happens.
I know that the 1961 - 66 Buick Nailhead had side loading issues with the valves. Replacing the rocker assembly with the 53 - 60 version fixes that problem and the problem of dimpled valve stem ends as well.
*Exact* same thing happened to me, except (LOL) it was a 1966 VW Type 3 Fastback with the 1.6L flat four air cooled engine. #3 Exhaust valve broke off and was munched. Cost me about $400 to have fixed by a local garage. Replaced one bent connecting rod, smashed up piston, and head; all good used parts. Same engine was later involved in an engine fire, destroying the car and merely damaging the engine. Same engine later caused a 1957 Beetle to pull a one-foot high wheelie, so there is that.
Great video. I am just wondering if buying a used Corvette with 60k on the clock and then extensively using the machine at wide open throttle is expecting too much from a production engine. From my own experience this seems a little hopeful. However, a blown engine is a sad day for anyone. Thanks for a very good presentation.
All of the breaking valve/lunched LS7 motors have happened to perfectly running motors without warning. The LS7 is a great motor, and it's reliable if you just bite the bullet and have the heads redone. I had my heads rebuilt with solid inconel exhaust valves (guides, seats cut, etc.) by a well regarded local shop for $1600, did the rest of the work myself, and with gaskets and such spent well under $2k for peace of mind. I'm not scared of LS7s nor are any of my many friends who run them. The 2 pairs of LS7 heads I've disassembled (with 16k miles and 38k miles) had similar guide wear (four heads averaged 3 guides each with at least 3 thousandths of elongated wear, and most were intake valve guides). Just my experience.
I have almost 120,000 miles on mine. So. far, so good. I was very careful doing the initial break in from new. I've been using Amsoil Sig Synthetic with the first oil change at 1100 miles. Up to 50,000 miles, I'd been sending samples to Blackstone. Same thing. No issues with metal contamination. And, I've been on a race track three times. Can't say if it will or won't ever happen. Just keeping my fingers and toes crossed.
It makes sense that the oil analysis showed nothing. Valve wear wouldn’t make it to the oil system but rather straight to the combustion chamber. Oil analysis is still a good health check for bearings, rings, etc
I want to know. Did the valve head break off. Did the valve stem break off in the guide. Did the valve stem break off above the guide but below the keeper grooves. Did it break off in or at the keeper grooves. Did the keepers fall out and drop the valve. If the oil temp got up to 275f. What was the coolant temp. If the combustion chamber around the valve seat is broken. How thick is the supporting area. This might require careful band sawing the part of the head into 5/16 thick slices like a loaf of bread to see if there is enough support under the valve seats to prevent the valve seat and pocket from shifting that will cause the valve to come down on one side of the valve face before the other causing excessive flex to the stem and failure. I would love for you to have a long allen head bolt modified. With a slight undercut to the underhead and reducing the head OD to allow you to pull the valve guides out intact. So you can cut them open to check the wear pattern. Are there any obvious wear marks on any of the valve stems. Are you going to do die penetrant testing on the other 15 valves. Examining the broken valve facture points. Question. Are titanium valves needed to reduce valve train mass in engines that wont see well above 8k rpms. I hate hypereutetic pistons. They are just cast pistons with higher percentages of silicon vs aluminum . Oems like them as they can run a tighter cylinder bore clearance as they don't expand as much as a cast piston or a forged piston. But are as brittle as glass. Many years ago i was forum moderator at circle track and stock car racing magazines and i started threads in each about fuel level angles in the carbs. On the straights the fuel level would be high on the left barrels and on the corners the fuel would be high on the right. Totally effecting max power. I think this is why autolite designed the inline 4 barrel but that is before my time about 10 years. I also brought up oil pan levels. I wondered if somebody at GM saw that and built the LT1 tilting dyno.
Sorry about your engine...Really sucks....Great no-nonsense video though on the issue. For years I've heard so many conflicting stories on the problem on the LS7, you explained it clear and concise. I have a C5 Z06 (LS6) with similar mileage and it has very bad piston slap when cold, I just live with it. I haven't heard of any valve drop issues with those but now I'm worried.
Ls1s don't have valve drop issues however if you have a ticking noise, check your rocker arms, they are notorious for losing their retainers and dropping needle bearings causing the rocker arm to lean and giving a piston slap sound, happened to me
Valve springs on the LS6 was the biggest topic I heard about and some concerns about the water pumps going out before it was time to. Other than that, LS6's are bullet proof. I think FluffyGear hit it right about your problem.
If your C5Z is a 2001, they are known for the cold start piston slap. If 2002-2004 (they fixed that issue), I would suggest tearing it down before you have a more serious issue.
Never use cheap oils with an even cheaper base in a track or race vehicle. Mobil 1 has had extremely poor quality oil for almost a decade now. They've even been sued for labeling their oil as full synthetic when none of their oils actually are. I highly highly recommend sticking with good quality brands like Amsoil and their Dominator series, or Motul and their 300v series.
I do wonder why you assumed an engine with a decent amount of miles would be better off than one with less... I mean your extremely detailed video breaks down exactly how it is an excessive wear issue.
This is due to the valve seat not being concentric with the valve guide , so every time the valve closes the stem is bent slightly , causing fatigue failure ...
As a huge vette fan and owner (C5), I had no idea this was even an issue. I feel like if i was in your shoes, i'd replace the engine with a destroked ls7 build. I've always wanted to have an ls2 or ls7 with a forged 4.8 crank in it for the high rev range. I feel like it would be huge fun, just remember to change the valves ;). Its unfortunate this happened though, good luck with whatever you replace the ls7 with.
The stroke doesn't have anything to do with high rev potential. RPM limit is controlled by the size of your wallet & the quality of the valve springs, valve train components & othe reciprocating. My buddy turned his 555BBC 7500+ & ran it 13 seasons in his 7.97 second/168mph Super Comp 86 Olds Cutlas. He is now turning his 440ci Small Block Olds 8500+! 500ci NHRA Pro Stock engines are chipped at 10,500 & were turning 11,500 before the RPM rule & NASCAR was turning them over 10,000 before the gear rule to lower the RPM to help lower costs because they were changing valve springs 3 times per weekend at a cost of $3,000 per set. Pro Stock springs have higher seat pressures than most valve springs ever see at peak lift.
Aftermarket block,factory rotating assembly a good set of aftermarket heads that would clearly out flow the factory heads. Ditch the titanium crap an go with the tried and true inconel exhaust and stainless intake,mild cam upgrade and very good set of long tube headers. This would make what ya had with more power then before as well as sound much better with the headers and imo be bout as close as bulletproof as possible that a large displacement engine can be and judging by the thing you was speaking bout it would last you till you sold the car. The reason I would stay away from supercharging or turbos just any power adder is many never take into account drivetrain upgrades needed to make it reliable. This would make more power as it would flow more air more efficient have a better block made with better quality control as well as in smaller batches and not mass produced and valve issue wouldn’t be a thing but I think I’d do one more upgrade and that’s shaft mount rockers as it would put more insurance on not having any valve drop issue.
Changing valves and guides pr even heads is a band aid. Ls7s need a high quality roller rocker system that is properly set up at a point when there is no valve/guide wear.
It knew you weren’t wearing new balances and rejected your ownership
He's wearing them in the video so looks like he learned
Bahahahaha!
LoL! Prob had Nikes on. Get woke blow up.
🤣🤣🤣
2nd owner things
It’s about $2,500 to $3,000 parts and labor to have this issue fixed before you drop a valve. Every LS7 should have the valves updated.
Seems like a good excuse to put some performance heads on! 😀
Treat them as if they have a finite life, and replace them *PREEMPTIVELY?*
As in “Lifing” - much like Formula 1 supposedly treats some of their parts…
Its the valve guides not the valves
no thanks. i’ll take my chances.
They still drop valves even after "fixed heads"
As a retired GM dealer head tech: (ASE Master w/L1 cert.) 40+ years in the buss. and 30+ in a GM dealer I can honestly tell you that GM is the KING at gaslighting!!! Generally when you call about something that will be VERY COSTLY they start to deflect. It's like the old saying: ( If their lips are moving they are lying) Retired 6 yrs now and don't miss one damn thing about dealing with people like that!!!
That’s a really refreshing take from a GM professional. I was in the car business and lost so much money with the GM 3.6L DOHC 24V V6 timing system. This is very surprising about the LS7 pushrod.
That's every car maker
Why as a retired 40 year automotive veteran I always printed the recalls/TSBs, and handed my customers the mechanics notes and any photographs before I sent them to the Dealer.
I’d tell them to hold back and just ask. The dealer would always blow smoke up their behinds and my customers would hand them the stuff and ask when the car would be ready. Both GM dealers here hate my guts. 🖕’em!
My son broke a ring land on a tuned 30k Ecoboost. The tune Ecoboomed the motor. Ford bought him a new one. COMPLETE motor. Gratis! No charge! GM would have said “No warranty due to aftermarket tune” and sent him packing. 💯 %. Ford bought a 25 year old customer for life that day. He’s about to go buy another Coyote Mustang.
They sure have taking the effort to fix the AFM/DOD lifters too...
I have my conspiracy theories that when they took the goverment bailout alot was in that paperwork......
@larrygreen9100 I really am a team player but it's hard to care when no one else does. Wondering how upper management took the 10 cents ignition spring tragedy, "isn't it time for your break Larry?" We avoided the Takata air bag fiasco by one model year. A new shotgun with every purchase right there in the steering wheel!
It wasn't certain years or a bad batch, every LS7 across all the years is suspect!
I can attest to that.
@Ralph Depino Yes.
@Ralph Depino . Yeah . A whole new ENGINE is quite inexpensive................................
@@johncunningham4820 buddy hes talking about pulling the heads before it happens.....
Agreed!
As a machinist, you just have to understand the materials, it make perfect sense to why this happened, Titanium has a coating over the material when the coating wears off then Titanium will gaul and stick, so if the valve coating is wearing away, then most likely the Connecting Rod Coating is doing the same, Bronze will not gual Titanium Valves, going to a Stainless Steel Valve or a Bronze Valve Guide will prevent this, Its time to start looking at the connecting rods before you have a major failure.
Greetings from New Zealand. Thanks for the video and condolences on the blown motor. I have an '07 Z06 which I purchased 2 1/2 years ago. Went for a test drive with the then owner and I just had to own the car. At the time it had around 27,000 miles on it and in the interim I did some 'due diligence' on the LS7 head issue and negotiated a better purchase price. I sent the car to a performance engine shop for checking. The 'wiggle' test was hopeless, so made the call.... The Intake valve to valve guide clearance was top limit and the exhaust was 50% OVER top limit. In addition, one of the trunnion (rocker) bearings was in the process of collapsing. Thank god we checked it because the wife would NOT have been happy. Because I'm an 'old fart' of 70, and will never drive this to it's potential, we fitted 1/4" longer valve guides (better valve stem support) and stainless valves. Still have the Titanium valves if the next owner wants to retro fit. All the best with the 'fix'.
Thanks for such a thoughtful comment! You're much wiser than me for getting that all checked out and fixed. Happy driving!
Rob, what part of NZ are you in? I am in Auckland and also have a C6Z06. We should catch up for a coffee.
@@KelMcBeath Hello Kel. Sorry for the long delay. We live in Waihi and don't get up to Auckland very often in the 'Vette. Would be good to catch up though.
@@KelMcBeath so did you guys meet or what? I'm invested in this budding friendship now 😂
@@MotivEngineering LOL if valve drops such an issue why not just replace the heads with better aftermarket ones to prevent this issue in the first place?
Vengeance Corvette in Atlanta had a special running that replaced the heads with stage two cnc ported heads with bronze guides and I chose Manley severe duty stainless valves. I think the total bill was about $3500.00. No matter how many miles you have on an engine, get the heads changed out and be done. Anyone who has driven an LS7 would not be happy with an LS3.
LS3 with a supercharger?
@@ghostwrench2292 Nope. There's just no replacement for the raw feeling of 7 litres on a lightweight car.
@Yuu Z yeah, they also used this engine in the z/28, that must've been a hell of a lot if fun. No one ever really talks about that car.
@@remissiveslave hardly no one knows the car even exists if you think about it.
@@remissiveslave I never even seen one, I honestly didn’t really know if was in production for that time
Good to hear that you weren’t inside the cylinder during failure. Always risky hanging out inside the cylinders!
There will not be any contaminates in the oil, these valves fail from the fusion weld of the exhaust valves. The valves in the LS7 are hollow and the actual valve is friction welded to the stem, this is the failure point and there is really no way to predict the failure.
That’s very interesting. I was not educated about how Del West manufactured them.
This is very interesting 🤔🧐 indeed
Was wondering if anyone was going to bring this up..
Hollow valves are a trade off.. In the past they simply made the valve, then EDM plunge drilled them and filled them with sodium and plug weld the top end.. Gm tried to get fancy and microweld the shaft. Not the best process for this.
I don't think the Del West intakes are hollow or fusion welded. The hollow stem valves are barely strong enough even when hitting the valve seat evenly but throw in a massively worn guide and the poor valve gets side loaded to the extreme, flexes then snaps the head off. It's always the exhaust valve that drops first. I have measured hollow stem exh valves that looked like the stem almost collapsed into an oval with a relatively intact guide. They are junk!
been in a big name OEM and race automotive engine testing lab and the first engine that blew under my watch, blew a rod out the side from a dropped valve was an LS7 back in 2005.
Was this in building 93?
Bs
It decided that it needed an inspection port
As a heavy equipment technician for a fleet with a lot of experience analysing oil analysis I can tell you it is one useful diagnostic tool. I've used many oil sample analyses to solidify a diagnosis or even prevent a failure occurring. But with that not every failure is detectable or preventable even with the best of maintenance. Some defects can create stress points that don't show signs until it is absolutely too late. For an example most Symptoms of EGR cooler failures are detectable with an increase of potassium and sodium in engine oils, but I've seen clean oil samples where the cooler suddenly dumps coolant into the engine hydrolocking it. Data is important, but you seem to forget one thing, variables and endless and can change or even hinder data useless.
You are 100% right on. Retired now, at one point in my 44 year career, was the fleet manager for an ambulance company. We were running Ford 7.3L turbo diesels. I had the mechanic do oil sampling every 25,000 miles on 22 ambulances. Never had a lot of problems but we did have a brand new 7.3 develop and odd miss and performed the oil sample and discovered a bad cam with infantile failure due to a surface hardening failure. Warrantly replaced the cam and kit including all pushrods, roller rockers and roller lifters. Problem solved no more issues and SAVED an engine.
I love the way these ls7’s chop with a big cam at Idle!
I currently own a 2015 Z 28 with 35,000 miles on it and have always debated on this issue I’m gonna pull the trigger and get the heads fixed and of course while it’s open upgrade the cam and have headers and high flow cats install the same time I just think it’s peace of mind the car it’s an absolute joy to drive and I love it.
I think the at risk range are the 2007-2008 engines
Have you done this yet? I have a 2015 Z as well. I thought this issue was fixed during the Z06 corvette run.
@@Waynegs3 its EVERY LS7. Do not encourage people to risk a 20k motor on some "I think" statements
This is why I went with the c6 grand sport. More or less the same price without the fear of exploding a $15k engine.
I certainly don’t fault you for that decision. The “I’m part of the cool LS7 club” is way less cool when I’m standing at the side of the road waiting for a tow truck.
Usually cheaper, more reliable and available engine, and you can modify it for z06 performance relatively easily.
grand sport aka wide body base model. no thanks.
All you gotta do is put 3-4k into it doing a good heads cam package and you don't gotta worry about dropping a 15k dollar engine lol. And you'd be as fast as many ls3 with boost.
@yung tooli this is the worst argument for the Grand Sports, considering they have a lot more goodies than just a "wide body"
Got my C6Z06 LS7 with bad bearings and still ongoing rebuild... Lots of headaches about new bearing clearances and parts that are on backorder by GM though... I'm quite interested about the oncoming project of yours and surprised your Oil analysis did not help spot any problem beforehand.
This is the first video I've seen of yours and instantly subscribed. My jaw dropped when I saw behind the throttle body.
If you haven't decided already, I vote stroker ls3 with mild cam. They're great.
I'd have to say that I would certainly agree with your reasoning on being comfortable with this engine prior to it's failure. Just goes to show how much of a beating a valve can take when it's in a situation that can lead to failure. I'd put an LS7 back in it, lightly modified in the manner of your choice as compared to what you had.
6K gets you peace of mind. When buying one of these just factor that into the cost and have the valves replaced is my 2cents
It costs closer to $3,000 parts and labor to replace the valves on a LS7.
@@KeithKman where you live perhaps.
I’ve recently had this work quoted at 3 shops and then performed at RPM in DE
@@mikec6447 you had it done by the best, I’m sure Fran and crew got you all dialed in.
If I'm buying a fairly low mileage used one from a dealer, you think they'll be willing to lower the price if it has stock heads or they don't care about that? Selling my 14 paxton coyote next week & plan on getting a c6z
jesus these shops see you guys coming, valves cost like 600 bucks for a good stainless set.
Best video I've seen on the LS7 valve drop issue. Pro video quality and editing as well. Subscribed.
It's just my theory, but it's based on an experience I had with an early 5.7 V-8 that suffered from valve guide problems at moderately low mileage (60,000 mi.).
The LS-7 came equipped with a lot of performance upgrades, with the exception of one thing, roller tipped rockers. GM made the leap to roller camshafts in the late eighties but neglected the one component that enabled the cam to do it's job without causing damage elsewhere.
Roller cams have steep or short duration valve opening event ramps, which accelerate the rockers from static to in motion in fractions of a second. It is my opinion based on my experience that this instantaneous motion causes the rocker to not only push the valve stem downward, but additionally, it tends to pull the valve stem up toward the fulcrum of the rocker due to friction between the rocker and stem end. This creates excessive side loading in the guide, causing premature wear and eventual guide failure.
In my case, it showed itself by excessive oil consumption via the guides, but with continued use it possibly could have led to catastrophic failure. It eventually led to a complete engine replacement that GM footed the bill for.
This makes sense. I couldn’t see play between the stem and guide alone causing this. I have an olds 455 that has some really gnarly play in the guides, enough to hear and I regularly rev it over 6k rpm without letting it warm up sometimes. Not that one engine proves anything but it has roller rockers and haven’t had an issue. So I was thinking if any motor was gonna drop a valve from having play in the stem it would be this one 😆 so I’m on board with the side loading idea.
Brutal and another reason why I got my heads fixed prior to really driving mine. Sub'd to see what you guys end up doing!
There are plenty of LS7's that still drop valves even after "fixed heads". Be careful
@@hsucduwwhat’s the solution to preventing them from dropping if fixing the heads alone isn’t enough
This is a relatively exotic engine, materials wise. I wouldn’t expect it to go 100k mi w/o extra maintenance. The valves are Titanium and need to be monitored for elongation. When lash shows the valve has stretched 0.010”, throw them away and put new in. Don’t expect the Titanium con rods to last forever either.
Yeah, people don't realize that titanium is a wonderful material - about as light as aluminum and strong as steel - but it doesn't last or wear like steel. Titanium engine parts should be checked and replaced regularly as wear items. I'm told they're more prone to metal fatigue, a bit like aluminum.
Damn..
I have seen Japanese motorcycles get 100k on their titanium valves without issues. They are turning 11000-13000 RPMs, but they also are 4 valve motors. They usually are 31 to 33 mm valves also.
@@cyclonebuzz8172 I’ve seen motorcycles drop a titanium valve at less than 20K miles when just riding along. Kawasaki had a lot of trouble when they first went to titanium valves. I think because they were a two piece valve and the head of the valve would fall off.
@177SCmaro very true. Titanium didn't have a fatigue limit. It will continously wear until it fails. Just a matter of time.
As an LS7 owner who was scared to even drive to the grocery store until I got the heads "fixed", thanks for making this. There's a lot of back and forth out there and yeah, a TON of people (including Tadge at one point, I do believe) say as long as you keep it stock, you've got nothing to worry about. Haven't looked at the rest of your channel yet, but looking forward to going through it to see what build you decided on. I'm hoping to see an LSX!
Having a motor let go sucks and I feel for you, but: a Small Block Chevy that makes 500hp and runs for 15 years/70k miles (including track use) is still impressive. Not ideal obviously, but no small feat.
I have 30k on my 2007 Z06, stock, bought it a year ago, 4 HPDE days so far. Read all the internet stuff, decided I'm not touching a running motor, fingers crossed. This video is very informative, thank you for posting it.
Adam, I don’t disagree with you at all. You obviously understand my mindset after watching the video. I was nervous to open up something that had been working so well for so long.
I certainly hope that you have better luck than I did. Keep an eye on it, I’ll be crossing my fingers for you too!
-Mike
A heads and cam package would do wonders for piece of mind. That’s what you tell your old lady anyway. I lost my stock motor to ring butting under boost. Still faster than a lot of cars on only 7 1/2 cylinders though. Shockingly seafoam didn’t bring back my compression🤷♂️
I would do a heads cam package it wakes the car up big, sounds badass, and eliminates this issue.
Can't agree that it's impressive, 7.0L engine with 500hp, 5.5 mercedes, m113k will do over 500k ? How come all the previous ls engines lasted so much longer ? I would be pissed if my hypothetical corvette blew up at 70k
@@dietznutz1 ruclips.net/video/lUAB7lKoIt0/видео.html
The head Corvette tech at GM said the valve drop issue occured only on a small handful of engines first produced in 2006. The problem does not exist in 2007-2013. Internet folklore.
Hey man, I don’t think you’d see anything in the oil at all before this failure as it’s not a progressive failure. Most likely the valve stem’s non-conformance to the design tolerances caused the valve head to be subjected to a small elastic strain every time it closed as the head was closing on one side of the seat first. This would cause high cycle fatigue in the neck of the valve, causing an almost instantaneous failure as it finally fractures.
yes someone gets it
Bingo
In the preview picture, the intake valves look sunken in the combustion chamber. This type of drop can also be caused by recession. This can be detected before failure. There are wear particles but those get blown out the exhaust. Instead, recession can be tracked by measuring valve protrusion. Intake valve recession is often caused by running aftermarket air filters that pass dirt.
Based on the known probability of occurrence of the failure event described. I suppose a new owner of a used LS7 should simply weigh whether setting a corrected set of heads on the short block, or simply driving it as is.
If you have a LS7, do the upgrades to fix any potential issues. As far as what engine to replace it with depends on what you mainly use the car for. Sounds like you love track. So go with what you is best for you.
The problem is, there is no "THE" upgrades. There are all kinds of theory on why the valves fail. SIde load on the valve, valve material, valve guide material.... No one seems to metion valve springs - but I can tell you a bad valve spring can break a valve (side load placed on valve).
@@confuse9 Agreed. Bad valve springs can cause issues. But the LS 7 is a new animal. It has problems that go beyond valve springs. It's a great and powerful motor, and would to love one! But these motors experience problems way before they should!
This is a fantastic video. I made one on my channel a while back outlining the issue and offering a clear warning and suggestions. Many people criticized that warning and called me every name in the book except for "logical". I have no interest on rolling the dice...I got mine fixed and made the odds a bit better for my Z06...which I truly love.
I’ll give yours a watch too! Thanks for the nice comment. As to replacing yours early: you obviously are a smarter man than me haha.
From what I learned. The centerline of the guide and the centerline of the valve seat are not in line. A brand new head was measured before being installed, and that is where this conclusion came from. The bare head was a replacement under warranty, and the associated parts were loose. The machine shop had a pristine head to check tolerances and found things out of alignment. 2007 Z06, heads fixed, and Crower shaft rockers installed.
Asked my warranty carrier if they would approve a pre-emptive repair and they said no. They wound up paying a 23,000.00 claim. Then we started with a new 5.3 truck block, installed darton dry sleeves, properly machined and ported LS-7 heads, etc.,etc. Now I have a 440 c.i. beast that is awesome to drive on our local road courses. Many thanks to LME!
But hey GM says it’s not an issue so your engine is 100% fine
Just like the experts said about covid shots.
@@browningbelgium2326 yup
Lol
This sounds oh so familiar. My LT4 is heavily modified, I had a water pump failure and couldn't pull over immediately, by the time I did. I had already done crazy damage. The heads had been redone with .660 springs, trunion upgrades, etc. Typical mods with a cam. Pulled valve covers, found #7 cylinder with spring still compressed, valve was missing, had the block re-sleeved, new forged rods and pistons, 3 days after getting the car back, it dropped #6 valve and beat up #6 forged piston. Found out the springs were re-used in the new heads. The shop is now rebuilding it , at their expense!!! But I don't have much trust in it at this point. My faith in my machine has seriously been disturbed, at this point im just hoping it holds together. The fast car effort is seriously overrated in my mind, at least until I can gap somebody and put it back into perspective.
We had a c6 zo6 at the shop about a year ago, the way the engine failed seemed to be similar. Total destruction, you could look through one side of the block through the other, it had holes on both sides. The only mods were an intake manifold and exhaust
Sucks to have this happen, but the good news is it gained my sub. Looking forward to seeing how you deal with this unfortunate experience.
I've never see more cars blow up at HPDE days than the Z06.
Yea with their modified cars this car is hand built with precision the LS7 does not respond well with modifications a totally bone-stock LS7 engine very seldom any problems.
@@richardcerritelli9657 oh come on man, lots of stock LS7s have come apart.
That said, I'd still own one.
How do you know they were stock. 2008 through 11 had a small issue and the internet blows it up like they would exaggerate the bottom line when you modify these cars that's when you fall into problems especially the C6 Z06 it's a hand-built specialty engine that does not respond well to modifications.
True...second most engine track failures is the Ford GT350's. I've personally witnessed 3 of them .....and three C6 Zo6's
Because they modify them. The C6 Z06 does not respond well to modifications that engine is hand belt and precision for stock configurations when you listen to the Corvette forum they don't know shit the people think they know it all one person modified their car it blows up and you'd swear a million cars all ZO6 cars have the same problem it's bullshit.
Had this happen 2 years ago after a cam upgrade, the car ran fantastic at the dyno, after i got home and took it back out. Around 2nd or 3rd gear spirited run it just did a quick pop and smoke from the engine.
About 8months later, new build : ls3 block bored out with darton sleeves, larger forged pistons, step up larger bore, replaced the one broken titanium rod, everything was fine, kept all the ls7 components ( rotating assembly etc).
New set of stock ls7 heads got the entire vlave job completed, kept the titanium valves, upgraded the exhaust to ferrea ss.
Tsp stage 2 cam
Rocker bushing upgrades
Msd intake.manifold
Nick Williams TB
Basically all bolt ons with extra major internal upgrades, ran 630whp at the dyno and revs to about 7500rpm.
Next upgrade will be Vengeance Performance head work, upgrade fuel injectors, and id say gra few extra HP with harmonic balancer and a ported msd intake manifold.
I should be able to get this monster to 670whp NA on 91 octane
At the most maybe ij the future a procharger running 3lbs for thst extra 50-80hp lol not sure i can get anymore power NA after the heads / msd porting
Holy crap you’re building a monster haha. That’s awesome to hear, good luck with it!
@@MotivEngineering ya no doubt.. Although chasing electrical Gremlin now
It seems to me that you have direct evidence from Blackstone that this wasn't a wear issue. Or at least, the amount of wear that occurred prior to failure was slow and steady enough that it didn't show up as abnormal. This was my biggest fear that prevented me from buying a C6 Z06 - the valve issue is not wear related. It may be a problem with the design where the components can be within the manufacturing specs and still have insufficient strength to stay together over time. Fatigue failure rather than wear failure.
And my research indicated that some of the aftermarket fixes might not be reliable either. Failure can happen at any time and there's no perfectly reliable indicator. This is similar to why I sold my GT350. I know some owners never have a problem, but the risk wasn't worth it to me.
I would consider an LS3 or some other version of the LS as a replacement to avoid recurrence.
Valve failure will never show up in the oil. I’m pretty positive the ls7 have hollow stemmed valves. They are super light weight, but in return they tend to be brittle and unable to stretch, so there is no wear evidence, they just snap eventually.
Yikes! Definitely rethinking that LS7 swap in the GTO I was planning.
Just get some better after market heads the bottom end is fine
It's so easy to fix just put a good set of heads on it with stainless valves. Heads cam should be the first thing any ls7 owner does. Why not? You make the car sound wicked and run way better and eliminate this issue all at the same time.
@@midnight347 only thing is, stainless valves weigh more, and valve float is a very bad thing. Make sure you have the proper springs to control those heavier valves. Or go sodium filled very pricey
@new71owner yea this is true. It can be remedied just gotta do your homework.
I bought a Grand Sport for 2 reasons, 1st was the removable top 2nd was the valve drop issues, I did want a Z06 and almost pulled the trigger on one but honestly the valve drop issues is something I could never be comfortable with driving the car wondering if the damn engine is going to blow up every time I run it hard.
Bought the same car, for the same reasons. Gonna be adding AP Radi-cal brakes and a race seat/harness for this upcoming track season, which I'd rather be doing than replacing an engine. Sorry to hear this news, and I wish GM would admit real numbers on these problems, but alas we all seem to get black balled when it's brought up.
We are in the same boat!
C6Z owner (it's been my daily for years). I knew the risk when I bought it. I considered the GS or a ZR1, but I got a GREAT deal on the C6Z and also had to have that 427! Even if it nuked tomorrow, I wouldn't regret the purchase. With that said, I will be doing aftermarket heads, cam, headers, MSD intake, and TB soon. Partly for piece of mind, but mostly for the additional 175-200hp. I have an LS3 in the car in this avatar and it's a great engine (and handles boost better than the LS7), but the higher revving LS7 with it's larger displacement really has my heart.
BTW, does the C6 GS have the aluminum frame like the Z06, or is it steel? What about the CF/balsa floors?
I could never buy a Z… I want the targa top, and the runflats. The end goal is a built LS7 swap for my c5
GM has too many engine problems don't know who's to blame and don't care.
Thank you for your video. Very well done. I appreciate your detailed information. I'll be applying the lessons you learned to my car shortly.
The exhaust valve is a two piece valve and they brake off where they’re fused together.
Yeah those hollow ferrea valves are drilled out from solid. I think hollow ss intake and solid ss exhaust is the way to go for reliability. Also roller rockers. TFS has the best flowing small runner aftermarket ls7 heads, add yella terra rockers and hollow intake it will be ready for anything. Mamo motorsports builds on this setup, that's my route.
I'll check that stuff out! Thanks for the advice!
I’m glad I picked up a ls7 bare block for my chevelle and built it from ground up with brodix br7 sts heads with bronze guides and SS valves! The dropped valve shit sounds stressful!
My Corvette specialist said if you're at nearly 50k miles, your chances are lower, but not 0%. They said if you plan to track the car, you should do the heads anyway.
Good advice!!
I bought a 8,500 mile Z and the first thing I did was fix the problem via Lingenfelter performance. If you buy the car understand this is not an option. And honestly it’s a great first mod. Gives you a chance to upgrade the valve train , new head gaskets and CNC port the heads. My car makes 531 with no cam , just fixed heads and intake.
Mine had connecting rods rubbing. Found that with an oil sample and then an in-depth look at the oil filter media. My car had the heads “fixed” by lingenfelter when I bought it.
I asked the shop to check the heads while the engine was out. Valve guide to stem wear was excessive. Lingenfelter will not stand behind their work nor would I trust them to “fix” their mistake anyway. The exhaust valve seats were already leaking too.
Heads are being sent to AI in charlotte NC.
Block is being fitted with Eagle forged crank, K1 conn rods, Carrillo pistons BTR stage 3 cam, new lifters, trays, &pushrods. Doing the CHE trunion upgrade to the rocker arms, Manley stainless steel exhaust valves, AI bronze guides (maybe new intake valves too).
Kooks 1 7/8, 3”x pipe and McLeod clutch with bleeder. That oughtta fix it lol
put a set of TSP roller rockers or else you will be in the same boat with worn guides..... again
My c6z got 85k miles on the clock, the oil sample looks clean and I was thinking the same... If it will drop it should have already been dropped.😢 Damn now I'll get my h/c done sooner
Oil sample not going to tell you about Valve Guide or seat issue
I rebuilt an LT1 from 1996 replace rebuilt everything except pistons. I put 3500 miles on it over three years with no issues. It dropped a valve on start up one day. I drove it home. Still had oil pressure to the upper part of the engine. Pulled it apart, piston was dented but not bad, had the head fixed, new valve, new guide, cleaned up surfaces and reassembled it. Started it up and had no oil pressure to the top end. You may never know what happened to cause the valve to drop. Seems odd it dropped after all that time, but no matter the milage, running any engine hard calls for routine checks / inspections. Hope you can figure out that happened, so you can avoid the issue in the future.
GM....designing things to fail for service revenue is our business model. Have a nice day.
Planned obsolescence is a real thing the big three put in.
Do you work for GM?
At 50K miles I dropped off my ZO6 with Katech in Detroit for a Stage 2 upgrade. I don't track the car, just some spirited street pulls from time to time. I'm at 70K now and my ZO6 is still running great. Fingers crossed the work Katech did while rebuilding the heads will ward off the dreaded valve drop.
After much ado, I couldn't do it, and bought a 13 LS3 GS. I can supercharge it. I wanted the steel frame.
And you’ll have many trouble free miles ahead. Enjoy!
LS3's can't handle more ghan 625 wheel if longevity and reliability is your brew of taste. I know many guys on their 2nd and 3rd LS3, supercharged and right around 615 -630 wheel. None of them have a gm V8 anymore.
The LS7 was also noted for breaking valve springs, which allowed the valve to contact the piston. My neighbour's '06 developed a miss, luckily at slow speed a couple of blocks from home. Fortunately, the spring still kept the valve away from the piston. I replaced the broken spring with the head on the engine after a leakdown test verified the valve wasn't bent and it has worked fine for 5 years now. I did recommend replacing all of the springs, but he is cheap. lol
You could always check the valves by taking the valve covers off and wiggling the valves. Also its super easy to just get new valve guides installed. Also its shitty how GM never truly took care of this issue in their best corvette ever made.
Really love how your channel is narrated and documented. As someone that has worked on a few of these cars (c6zs specifically). They are insanely phenomenal cars that respond well to a cam and ported heads. I would do another stock short block or something similar as they are hard to come by and have the heads repaired and ported. BES Racing engines in ST Leon, Indiana has an amazing LS7 program that is world renowned
There are many factors to consider in any part failure . This is one heck of an expensive failure to have gone on this long !
I have a 12K LS7 and I'm terrified of what happened to you. I literally have one of the first sold 06 Z06 engines. I don't intend to ever beat on this at all but still keeps me up at night. Peace.
Nothing like dropping a valve for engine destruction!
“I thought I was safe because I had stock heads and never had a problem yet so I just waited until it became one” 😅😂 OOF. That hurt the wallet.
Yo why is this engineer so damn jacked? Asking for a friend
An LS7 with revised parts fixing this particular bug, that's what I'm voting for.
Would stainless valves live longer? Probably but you gain valve float & rpm
Short answer is NO! IF SS would take the heat & abuse the Ti valves withstand, all serious race engines would run them because they cost 1/10 the price of Ti valves. Weight is another consideration. The lighter the valve train(including lifters, pushrods, rocker arms, valves & retainers), the less the valve spring pressure required to control it. 10,500 RPM NHRA Pro Stock engines run 600+lb SEAT PRESSURE & crazy high open pressure to control big titanium valves without issue. The current method used in race engines of adjusting "installed spring height" is using the peak lift spring pressure rather than seat pressure.
GMs had the wiggle test for YEARS in the 80s/90s it was common for GM calling for "wiggle test" while diagnosing electrical problems , wiggling the entire harness from from to back to see if a fault spike occurs.
If you have an ls7 car don’t risk it you have a couple options you can send the heads out for a professional valve job, or buy an aftermarket set cnc ported heads, you could also send your heads to Texas speed or other head porting services to get a cnc port job and a good valve job, ls7 will make 70-100 hp more with just ported heads and a cam
make it an electric track car or a coyote swap! Or stuff the c4 ZR1 into it
Coyote swap 😂 sorry I’m a Ford guy and I had to do it. The first motor I ever blew up was a “built” 3 valve that was pro charged after a month of ownership. It lasted 4 years and after I tore it apart I found out the shop that “built” the engine just pocketed my money and threw trash parts into my engine. Lesson learned 👍
Put a Coyote 5.2 Voodoo in it.
So sorry, saw your post on the forum.
FWIW, I bought my Z06 with only 6k miles…and the AHP pkg 4 heads actually arrived a day before my car arrived. Just sayin. Turned out several valves were at, or slightly outside GM spec (and way outside AHP spec).
Would it have held? How long? Who knows?
Too expensive to chance it.
And yes…chance of failure obviously increases exponentially with aftermarket cams. Heck…the engine already has 1.8:1 rocker ratio.
I’ll also add that with such oil temps, I use heavier oil, moreover with much higher ZDDP for added lubricity. And try to keep oil under 250f (long story).
Again, sorry for your failure. I’d source another LS7 (stock cam!) and make sure the heads are refurbished. Good luck…and great video
It’s all okay in the long run. Lots of money will make it just like new again, or even better!
Enjoyed the video, well done - thanks!
This is where good quality machine work is worth it’s weight in gold, but good chance valve spring fatigue/lack of spring rate is the cause of this, and most certainly not oil contamination
Never heard of this issue before now, would probably just chock it up to the amount of WOT it likely saw in its life. Thanks for the video 👍
It's a performance sports car, arguably a super car. It's meant to see track use, and WOT. GM fucked up, end of story.
You sound pretty heated about it, did you lose one like this too ?
cant tell if you're stupid or just candian, well i mean both goes hand and hand so theres that lol@@TheCanadianBubba
I always used to hear Gwatney Chevrolet radio ads when living in central Arkansas. They are both in Jacksonville…surely must be related
This is the first of your videos I’ve ever watched. When you inserted the clip about the bird’s gizzard I fckn lost it man😂 had to leave a like
I wish I had seen this video earlier. Mercury Marine makes a dual overhead cam version of the LS7 that revs out to 7500 and makes great power.
Thanks for sharing. I owned a C6Z for a couple years. I miss how special that car was, but not the interior. With the valve issue, driving that car was like dating a stripper. Amazing and insane, but in the back of your mind you always had to be aware it could go very wrong, without warning, at any time.
That's why before I put my Ls7 back in my c6, I replaced the valves, the keepers, rockers, springs, and valve guides.....
Haven't had any problems whatsoever.
(Then again I didn't have any to begin with but did it anyways)
And BTW, I've seen the valve drop at low miles and high miles....it doesn't matter until it happens.
I know that the 1961 - 66 Buick Nailhead had side loading issues with the valves. Replacing the rocker assembly with the 53 - 60 version fixes that problem and the problem of dimpled valve stem ends as well.
That's good to know, I'll have to keep this in mind for when I restore my 66 Electra 225. Thanks!
Happened to me in 2015, just built a 433' ls7, first night out, pop
Very well done. Very detailed and cogent arguement.
*Exact* same thing happened to me, except (LOL) it was a 1966 VW Type 3 Fastback with the 1.6L flat four air cooled engine. #3 Exhaust valve broke off and was munched. Cost me about $400 to have fixed by a local garage. Replaced one bent connecting rod, smashed up piston, and head; all good used parts. Same engine was later involved in an engine fire, destroying the car and merely damaging the engine. Same engine later caused a 1957 Beetle to pull a one-foot high wheelie, so there is that.
So much for the glory and reliability of the "LS" lol. Hope mine never meets this fate..
Great video. I am just wondering if buying a used Corvette with 60k on the clock and then extensively using the machine at wide open throttle is expecting too much from a production engine. From my own experience this seems a little hopeful. However, a blown engine is a sad day for anyone. Thanks for a very good presentation.
All of the breaking valve/lunched LS7 motors have happened to perfectly running motors without warning. The LS7 is a great motor, and it's reliable if you just bite the bullet and have the heads redone. I had my heads rebuilt with solid inconel exhaust valves (guides, seats cut, etc.) by a well regarded local shop for $1600, did the rest of the work myself, and with gaskets and such spent well under $2k for peace of mind. I'm not scared of LS7s nor are any of my many friends who run them. The 2 pairs of LS7 heads I've disassembled (with 16k miles and 38k miles) had similar guide wear (four heads averaged 3 guides each with at least 3 thousandths of elongated wear, and most were intake valve guides). Just my experience.
I have almost 120,000 miles on mine. So. far, so good. I was very careful doing the initial break in from new. I've been using Amsoil Sig Synthetic with the first oil change at 1100 miles. Up to 50,000 miles, I'd been sending samples to Blackstone. Same thing. No issues with metal contamination. And, I've been on a race track three times. Can't say if it will or won't ever happen. Just keeping my fingers and toes crossed.
It WILL happen. Just be smart and take care of it before it completely totals your motor
@@jordanmascarenhas7974 🤞up at 122k currently 🤞
Actually, I almost lost the car due to a mission critical electrical part being discontinued that failed
It makes sense that the oil analysis showed nothing. Valve wear wouldn’t make it to the oil system but rather straight to the combustion chamber. Oil analysis is still a good health check for bearings, rings, etc
Lingenfelter makes a destroked LS7 longblock with different configurations. It’s about $20k but it’s a monster of an engine.
Mercury racing makes a 750hp timing belt DOHC converted LS7 as well.
I want to know. Did the valve head break off. Did the valve stem break off in the guide. Did the valve stem break off above the guide but below the keeper grooves. Did it break off in or at the keeper grooves. Did the keepers fall out and drop the valve.
If the oil temp got up to 275f. What was the coolant temp. If the combustion chamber around the valve seat is broken. How thick is the supporting area. This might require careful band sawing the part of the head into 5/16 thick slices like a loaf of bread to see if there is enough support under the valve seats to prevent the valve seat and pocket from shifting that will cause the valve to come down on one side of the valve face before the other causing excessive flex to the stem and failure.
I would love for you to have a long allen head bolt modified. With a slight undercut to the underhead and reducing the head OD to allow you to pull the valve guides out intact. So you can cut them open to check the wear pattern. Are there any obvious wear marks on any of the valve stems.
Are you going to do die penetrant testing on the other 15 valves.
Examining the broken valve facture points.
Question. Are titanium valves needed to reduce valve train mass in engines that wont see well above 8k rpms.
I hate hypereutetic pistons. They are just cast pistons with higher percentages of silicon vs aluminum . Oems like them as they can run a tighter cylinder bore clearance as they don't expand as much as a cast piston or a forged piston. But are as brittle as glass.
Many years ago i was forum moderator at circle track and stock car racing magazines and i started threads in each about fuel level angles in the carbs. On the straights the fuel level would be high on the left barrels and on the corners the fuel would be high on the right. Totally effecting max power. I think this is why autolite designed the inline 4 barrel but that is before my time about 10 years. I also brought up oil pan levels. I wondered if somebody at GM saw that and built the LT1 tilting dyno.
Sorry about your engine...Really sucks....Great no-nonsense video though on the issue. For years I've heard so many conflicting stories on the problem on the LS7, you explained it clear and concise. I have a C5 Z06 (LS6) with similar mileage and it has very bad piston slap when cold, I just live with it. I haven't heard of any valve drop issues with those but now I'm worried.
Ls1s don't have valve drop issues however if you have a ticking noise, check your rocker arms, they are notorious for losing their retainers and dropping needle bearings causing the rocker arm to lean and giving a piston slap sound, happened to me
@@ForgottenMuscle67 thanks...I'll check that out!
Valve springs on the LS6 was the biggest topic I heard about and some concerns about the water pumps going out before it was time to. Other than that, LS6's are bullet proof. I think FluffyGear hit it right about your problem.
If your C5Z is a 2001, they are known for the cold start piston slap. If 2002-2004 (they fixed that issue), I would suggest tearing it down before you have a more serious issue.
Never use cheap oils with an even cheaper base in a track or race vehicle. Mobil 1 has had extremely poor quality oil for almost a decade now. They've even been sued for labeling their oil as full synthetic when none of their oils actually are. I highly highly recommend sticking with good quality brands like Amsoil and their Dominator series, or Motul and their 300v series.
I'm sorry for your loss.
I do wonder why you assumed an engine with a decent amount of miles would be better off than one with less... I mean your extremely detailed video breaks down exactly how it is an excessive wear issue.
This is due to the valve seat not being concentric with the valve guide , so every time the valve closes the stem is bent slightly , causing fatigue failure ...
Torque is something else, but that high rpms are my cup of tea.
As a huge vette fan and owner (C5), I had no idea this was even an issue. I feel like if i was in your shoes, i'd replace the engine with a destroked ls7 build. I've always wanted to have an ls2 or ls7 with a forged 4.8 crank in it for the high rev range. I feel like it would be huge fun, just remember to change the valves ;). Its unfortunate this happened though, good luck with whatever you replace the ls7 with.
The stroke doesn't have anything to do with high rev potential. RPM limit is controlled by the size of your wallet & the quality of the valve springs, valve train components & othe reciprocating. My buddy turned his 555BBC 7500+ & ran it 13 seasons in his 7.97 second/168mph Super Comp 86 Olds Cutlas. He is now turning his 440ci Small Block Olds 8500+! 500ci NHRA Pro Stock engines are chipped at 10,500 & were turning 11,500 before the RPM rule & NASCAR was turning them over 10,000 before the gear rule to lower the RPM to help lower costs because they were changing valve springs 3 times per weekend at a cost of $3,000 per set. Pro Stock springs have higher seat pressures than most valve springs ever see at peak lift.
Every ls7 needs this addressed 😂 it’s been common knowledge since they came out. Just like the DOD failures
@Peter plenty
@Peter it’s nothing to argue prove me wrong with facts. Better yet go buy one and track it
@@Peter-nm1ps ruclips.net/video/23xClQU3138/видео.html
Aftermarket block,factory rotating assembly a good set of aftermarket heads that would clearly out flow the factory heads. Ditch the titanium crap an go with the tried and true inconel exhaust and stainless intake,mild cam upgrade and very good set of long tube headers. This would make what ya had with more power then before as well as sound much better with the headers and imo be bout as close as bulletproof as possible that a large displacement engine can be and judging by the thing you was speaking bout it would last you till you sold the car. The reason I would stay away from supercharging or turbos just any power adder is many never take into account drivetrain upgrades needed to make it reliable. This would make more power as it would flow more air more efficient have a better block made with better quality control as well as in smaller batches and not mass produced and valve issue wouldn’t be a thing but I think I’d do one more upgrade and that’s shaft mount rockers as it would put more insurance on not having any valve drop issue.
Changing valves and guides pr even heads is a band aid. Ls7s need a high quality roller rocker system that is properly set up at a point when there is no valve/guide wear.
Aluminum 427ci Sb2 would be super cool in that car!