tascar7

Like so many others I'm trying to follow all the activity about dropped valves in the ls7.

I was wondering if there is a certain cylinder # that fails more often than others.

Also when the heads are machined, are the ports cut one at a time or all at once?

BTW I have a very early production '06 with 16k and so far all seems well but I expect I will have to do a wiggle test soon at a minimum. I don't really want to replace the heads because I'd like to keep it as stock as possible. But it sure would be nice to identify a root cause of the issue. I think, as in most disasters, there isn't a single major mistake that was made but a series of minor oversights that combine into tragedy.



ps: I bought the Z because of the LS7-"If you're going to have a Corvette; have a 427!"

ctsv510

No there isn't one certain cylinder and definitely get yourself a wiggle test. You can keep your stock heads if they're out of spec, just send them to a good machine shop for a valve job and new guides and exhaust valves.

I have 17k miles on my '06 built in 11/05 and I had out of spec guides.

tascar7

I will have the heads rework probably. But that's one of the problems I having- If I rework the heads and use the same kind of parts then in 15k miles I'm back at the same place if the parts are the problem. If it's the machining, then I've correct that during the rework and should be good to go. However, if it's parts then what do I replace them with.? Have ANY of the many combinations out there been proven to 100k or 200k miles? I've put almost 200k on every vehicle I've owned in the last 25 years and have never had a major engine problem. I know the LS7 is a high performance engine, but it should still have at least 100k reliability.

double06

Take it to MTI racing or some of the other Corvette shops down there (Atlanta). They have enough experience to rebuild the heads and put the right parts in them (ie bronze guide) by now.

ctsv510

There is no guaranteed fix at this point but it looks less and less like a parts issue and mostly a machining issue. The only examples of 100-200k miles are on stock parts, and that's partly because not many miles have been put on repaired heads yet. It is likely those stock heads were machined properly and with that the stock parts have lasted just fine.

A good machine shop repairing your stock heads (if they need it) should be just fine for the long haul. As the years go on and people test these repaired heads we will know more definitively.

MarkC

Call Ron at Vengeance Racing in Cumming, Ga. He can fix the problem in two days. He did my car last year. The are a vendor on this forum.

tascar7

I've had one place locally tell me they have never seen a failure and another tell me that eventually every ls7 head will fail.



Though it seems if it is solely a machining issue (I'm inclined at this point to believe) then it should be identifiable if the heads were to be measured. Yes that would require removing and dismantling and rebuilding but would give some degree of confidence. I'm just one to not fix something that isn't broke (replace well designed pieces). I also one who doesn't mind correcting a flaw that may be more expensive down the road.

Landru

On an out-warranty LS7? IMO you'd be wise to do so, minimally have them measured.
If it were me I'd rebuild, pronto.
In spite of reported LS7s getting over 100K w/o issues, one doesn't know what cars are right until it's too late.

There's the rub, problem appears sporadic & totally unpredictable.
Key point: Replacing the motor's your responsibility IF it is 'bad' & blows.

Consider a new LS7 will be 5-6 times (based on ~$15K motor) the ~$3K for rebuilt heads.
YMMV but the numbers tell me which way to go for genuine confidence.

I've GMPP coverage on my '08 w/ 35K, if not for the GMPP heads would come off & rebuilt before I took another cruise.
Or, I'd flip it on a C7 --I really don't want.

0Myhardtop

This is simple - take your heads off, send to us and we will fix them. You then re-install and play with your Z without worrying about ruining your engine and paying thousands later to get it back to its glory self.

Got it?

http://www.theair-charger.com/vewche.html

Thanks,
Carlos

rio95

Great advice! Exactly what I'd do

Bill Dearborn

No particular cylinder stands out. My engine dropped a valve and was replaced by GM. Including mine I know of 9 engines that dropped valves. 8 that dropped exhaust valves and 1 that dropped an intake. The 1 that dropped the intake was repairable all the others weren't. That engine had an aftermarket cam so the owner paid for the repair himself and never asked GM if they would cover it. The others had stock engines and the replacements were all covered under GM Warranties of one sort or another. Mine was covered under a Good Will warranty.

All of those cars were heavily tracked seeing many track days per year and were driven by Instructors or Advanced Level drivers that drove them at much higher performance levels than the typical novice level driver does. What I mean by that is more time at or near WOT and less time on the brakes.

I have never heard of a non tracked stock engine that has dropped a valve. The data from several years ago when a fair number of cars were experiencing this failure is inconclusive on whether or not non tracked stock cars were actually experiencing the failure.

Are you at risk? Maybe. That means you need to check but that doesn't mean the solution has to be anything other than replacing the stock guides with bronze guides along with a new set of stock valves (The Katech recommended solution).

Bill

tascar7

And your warranty is for how long and covers what?

tascar7

Has the long term reliability been proven on this version of "the solution"?

Larry Myers

According to Katech, heads reworked to their specs. have experienced zero failures.

NavyAirTraffic

If I had to do over over again, I would send my Z to Lingenfelter for their 630hp package... includes the head work.

https://www.lingenfelter.com/engine-...cid-ls7-630-hp

Larry Myers

What I really like about Lingenfelter is their engine packages come with a three year 36,00 mile warranty. Compared to most other shop warranty's of perhaps a year.

Mark2009

It is rather unlikely to be the parts. There is a small chance that the combination of higher lift cam, higher rocker ratio, and intolerance of OEM guides to wear (once it has begun, for whatever reason) is creating a perfect storm of shot guides that was not present in similar GM LS engines (such as the LS6)... but that is a small chance IMHO.

If you want to hedge your bets go to a good bronze guide and the Ferrea semi-hollow valves which, in concert with a good beehive spring and a Ti retainer, will not bring any extra weight to the overall valvetrain (the lighter spring and retainer (compared to OEM) will offset the slightly heavier valve). You will lose some of the heat transfer capability that the GM engineers thought necessary when they spec'd the sodium exhaust valve. You will also be taking a slight wear risk running the OEM intake valve on a bronze guide (at least one highly experienced shop does not recommend that). However, that is the price you'll have to be willing to pay if you go off the GM reservation.

I'd say the odds are about 50/50 that a well machined head with all OEM parts will not experience any abnormal wear, at least with a stock cam and stock tune. Even if the car is tracked or otherwise run hard (keep an eye on those spring seats, GM apparently
went cheap here with an non-hardened part).
.

MTPZ06

You can always go PM if that's the case...

Mark2009

True, but only two shops that I know of willingly provide and work with PM guides... it is not a particularly popular option. In any case, that section of my post was to address the possible downsides of the bronze option.

At one point I was going to have PM guides installed on the intake and bronze on the exhaust, simply to satisfy the requirements of a vendor I was considering to do the wrenching. Ultimately I decided to do my own wrenching... we'll see how that works out (after the cost of tools and equipment I think I should have just paid them to do it )

MTPZ06

Agreed...but mainly due to availability of parts rather than preference IMO.

I imagine this to be correct...I will pay the piper when the day comes.