ByByBMW

There is a poster over on C6 general that just had a valve drop in his modified Z06, see here http://forums.corvetteforum.com/c6-c...hos-fault.html

I expect he will be here soon.

ORISALA

modified engine.

ByByBMW

Yep, just like I said in my post.

Witt748

keen eyes there

66biskwik

What I can't understand is why anyone would modify an LS7 and not do the head work. It's no secret that there is a valve problem.

morris

Because with all the bs it's not obvious that there is a real issue to a lot of folks, myself included. There is no rhyme or reason to the valve issue modified not modified high mileage not so much mileage. I had decided to just take my chances, that is until GM told me to have the valves addressed.

OJCrush08

The LG response to that thread is fascinating and that response should be posted over here. First time I have seen or heard of a top level vendor talking about GM in connection with LS7 valves...

Witt748

There is more rhyme or reason when you put a big cam in, lots of large cammed LS7 with no head work have popped over the years. I think that is one fact that most people in this forum will agree on. You throw a large cam in an LS7 w/o having your heads worked on and there is a greater percentage that it will pop, (no I don't have numbers to back that so I hope I don't get my head taken off for that), but it seems to be the case.

To contradict myself, it does become less obvious when you have top shops that use stock valves and guides on large cam applications without failure. I think you can attribute this to those shops studying their cams valve stress and by using top of the line valve springs. These shops are the minority though, I believe with most shops that will throw any cam in without doing head work, you're rolling the dice.

There is a reason so many cammed LS7's send their heads to WCCH. Sure adding heavier SS valves may not sound like the best idea, but for a lot of applications it's the safest bet. Even then you can't just beat on your big cammed car for 100,000 miles without changing your springs and checking for play with the valves. I think I will replace my springs every 10,000 miles.

So to clear up the fog, large cammed LS7 send your heads to WCCH, (there are other shops, but Richard does great work so I'll promote him )... unless you are doing your cam at a shop with a solid track record of their own cams with no headwork and no failures.

Stock under warranty, enjoy your car and stop reading these threads...

Stock outside of warranty... .

Nothings 100%, especially when modding, but this is about as safe as you can get.

Witt748

Unfortunate, I wonder if they recommended new valves to the guy whos engine popped? Or are they saying they recommend new exh valves to most high lift cams after they saw what happened to the OP's car? I guess because they looked good in the inspection they chose not to ask?... Sucks $2000 for reworked heads or $14,000 for an engine. I feel for the guy.

JetBlue427

Yes very interesting! well maybe just a bit interesting...cause seriously I cant believe anyone would be in denial of a head problem in this engine when we see weekly failures on such a small forum of owners.
At least certain members of this board cant quote LGs denial of the issue anymore...they will have to stick to Katechs response...but we all can read through the lines of Katechs response! well at least some of us can!
Hopefully someone comes up with a solution or theory before my warranty expires!

morris

I don't know Katech isn't exactly saying there isn't an issue, they have my car right now and are doing the heads for me. I elected to do them as a direct result of art spong head of GM quality control telling us it needed to be done. Actually he looked at me like I had two heads when I told him it had 30k miles on it

FrankTank

LG never flat out denied there was an issue, what they (Anthony) did say was you can't expect to mod a motor, or cam it, especially with a large cam and not check or modify the rest of the components in the head (ie valves). He said basically the same thing about Mobil 1 5W30..people can't expect to run the factory oil at temps over 260 day in and day out..it was not set up for that.

If you read that post, Lou also stated that is the 2nd failure only of an LS7 in the 6 or 7 years they have been modding and racing them.

What the debate is over is just how wide-spread a problem it could be or not...and also, what is the root cause?

2 questions there are no real solid answers to. Again lets be clear about it.

This post (and the one in C6 Gen about it) are nothing new, motor with large cam fails by dropping a valve. nothing we don't already know.

Cam this motor, and you better do it right and go through everything.

ConfusedGarage

Thank you for understanding how to look at and interpret the facts there. To have only 2 valve failures in 6+ years, you have to wonder how many they worked on. At the least a couple hundred? Even if the first failure was stock, and this latest was the modded one, I'd still be able to swallow that and sleep just fine at night.

Again, not saying SOME don't have an issue (clearly some do), but look at this particular shops experience as one piece of data. I think most out of warranty will find it worth it to drop the ~$3000 for a full WCCH job with new bronze guides, new OEM exhaust valves and katech ti/mo intake valves (or ~$2400ish if you take out the port/polish/milling) rather than wondering if you are in this small batch with issues.

If only those with cashed motors could provide anything along the lines of actual specs on guides, springs condition, surviving valves condition, rocker conditions etc., then we would know much more.

morris

I wish it were 3k they were charging

Unreal

You are correct, it is much less than $3k for new exhaust valves/guides.

Even paying someone to do the labor is less than $3k. Doing it yourself is <$1000.

morris

Sorry I wasn't clear, they are charging a lot more than 3k to do a full head job, yes it includes cnc porting milling new valves springs etc.

erikszr1

im a hot rodder at heart, through and through. i bought my 08 zo6 because of what it is. if a want something faster ill get a zr1 or build a race car. i see many guys modding these cars and i know for a fact they cant drive the car to its full potential in its stock form anyway.....then they mod, blow it up and cry cry cry.......waaaaa waaaaa. then they get towed into my Chevrolet dealership.....and i offer a tissue...

Witt748

The thing that gets me mad is shops who tell you that you don't need to have your heads done even when they are installing a big cam that isn't there own.

Maybe things have changed but last year I talked to four shops about having a large cam installed. Three of the four mentioned nothing about upgrading heads, (with the exception of new springs). One of the shops even tried to talk me out of it . The fourth shop said they wont do a cam on an LS7 without sending the heads to WCCH.

I just really think this issue should be brought up to potential customers before they stick an aftermarket cam in an LS7. Yes the customer should do their research, (and it's hard to miss all the LS7 valve talk online), but I still wonder about some of these shops... And I cringe when I see somebody at a car show with a cam installed by one of those three shops without any head work done. When I ask about it they tell me the shop never mentioned it.


great story!

chadyellowz06

read this mybe this will tell you why K wont say a word about it...it's comming out soon......read this..by the way k helped design the ls7head ..hmmmm....get those stock exhaust valve out they are breaking................................ ........................................ ........................................ ......To see just how much the Gen IV design differs from its immediate predecessor, we asked for help from General Motors performance-engine guru Mark McPhail, who recently left GM to head up Katech's new street performance division. Anyone familiar with the racing career of the small-block Chevy in recent years is surely familiar with Katech's Le Mans-winning engines that powered the C5-R Corvette to multiple class wins in the annual 24-hour endurance race. Katech has been joined at the hip with GM Racing during its 20-plus-year history and has recorded race wins in Trans-Am, IRL, IMSA, and the NASCAR Busch series among others. McPhail and his colleagues at Katech are pretty far ahead of the curve in Gen III/IV development, having worked hand-in-hand with engineers at GM on numerous racing and R&D endeavors during development of the platform, and they had all the parts on hand, including a just-arrived GMPP LS2 crate engine.

Read more: http://www.hotrod.com/techarticles/e...#ixzz23T9mGAYL

Keith N

WCCH quotes $1400 + shipping costs for LS7 heads http://proheads.com/pricing.html. Not including labor costs, so around $3K