kawaiilaosboy

Hey Corvette Forum! I need some opinions and help with a little problem I'm having. This past Wednesday, I went to my local drag strip for some fun. At the end of my pass, I lost power to my car and was running horrible so I immediately pull to the side and shut her down. I tried starting her up but she didn't want to. I check my connections and found them to be fine. At that point, I remember reading a few threads on Corvette Forum about dropped valves on the LS7s. I did not try to start her again and risking more damage. I had the car towed and decided to do a leak down test in the morning.

Morning came and we did a leak down test and found no compression in cylinder number 5. Now the fun starts. We pull the heads off to see what happened and we found this.

Piston



Valves



I found my valve in my cat and there is damage on the sleeve. I'm glad its was just one cylinder. My questions are;

I heard if we upgrade the valve springs, this problem can be prevented. What valve springs do you recommend for someone who does not plan on increasing the horse power on the Z06?

Is it wise to stay with the titanium valves or go with something like stainless steel for longevity?

Any comments or suggestions?

Thank you!

SmokinZ

Sorry to hear of your loss.

It seems that one of the solutions is to install bronze valve guides. But then you should replace the intake with ti/mo type (expensive) since it is more compatible with bronze. There is a big debate right now as to stay with the OEM hollow stem exhaust or to replace with a solid stainless steel valve. The SS valve may dissipate heat better and be able to handle the stress more but it is also much heavier. Because of the weight difference you will have to run a stronger valve spring which increases the forces and may reduce the upper RPM limit. I don't think just replacing the valve spring is a complete solution. Can you check for excessive wear in the valve guide on the failed cylinder? It will be interesting if yours has as much as mine did.


This is mine...

SmokinZ

kawaiilaosboy, did you notice any increased oil consumption or any hard starts as if the battery was low?

chadyellowz06

AHHH sorry op ..Guys get those exhaust valves out of your cars....use a soild SS valve and replace the guides with bronze

walhan_qtr

sorry to hear about your problems.

I have also seen a stock 06 Z06 with a stock tune drop an exhaust valve with about 30k miles. the car was driven very well and have only been to the track once with only a 15min session on street tires. have seen few high way pulls but never really abused. so really hard to say. again if it was me and since your heads are already off, I will do bronze guides, SS exh valves and keep the stock intake valve. will this fix the problem?? I dont know but it seems like a lot of people here think so and have had good luck with it.

EDIT: wrong info. my valve guides were all worn out.

vertC6

So sorry OP, what year is your car? Was it stock?

FrankTank

OP can we get some more info on your car ? Sorry about your car this sucks . If I were you I would contact one of the shops on the forum like Katech or Lg , livernois who have extensive experience with these cars .

Also if you are able have the guides in the heads checked I'm sure we'd all be curious to see if they are worn out of spec.

Random84

OP, it sucks that you have to go through this - but it looks like you got LUCKY!!!

Just a beat up cylinder head, piston, some machine work in your future and maybe a new sleeve in that cylinder (versus a window'd block).

Good luck with the repairs; and at this point I would at the least go with bronze guides but leave the parts/spring selection up to whomever you have work over the heads. Everyone might have their preferences, but most aftermarket head shops seem to stick with the stainless steel valves.

SmokinZ

Take a real close look at the block, mine had cracks in the block around the sleeve rendering it useless.

dun4791

seems to be a serious pattern here

TORQJNKY

If it's the same car in his sig, it's an 07 Z06 and doesn't list any mods other than Brembo brakes.

kawaiilaosboy

Hey guys. Thanks for the replies. Yes, the car is a 07 Z06 completely stock. I am a little high on the miles side since I'm at 70k. The only thing on the car is Brembo Brakes. I don't even have a CAI. I will be sending the block to the machine shop on Monday to be resleeved. One thing that came out positive is that I was able to tear this thing apart and learn from this experience. I never thought I would be seeing the inside of my motor. When I bought the car, I had the intentions of keeping her stock and just enjoying her. I guess I'm just cruised with just working on cars.

kawaiilaosboy

No increased oil onsumption and the car started right up when it ran fine.

I'll check the wear on Monday when my friend's shop opens.

So from what I gather from the thread is that LS7 owners are using bronze guides, using the titianiam valves, and keeping the stock valve springs?

walhan_qtr

SS exhaust valves, bronze guides, and stock intake valves. usually people that go through this do duel springs with a nice cam, but yes some use stock springs and stock cam.

there is no def answer to this. you will find some that thinks the stock guides are fine and there is nothing wrong with those LS7s or the heads. and will blame the owner (abuse, lack of maintenance, ...etc)

if it was me I will port the heads, bronze guides, SS exh valves, and do cam with duel valve springs

when you reassemble the heads make sure you or who ever does the work for you have the lash caps over the intake valves. a lot of people have messed this (including me). if those are not on it will drop a valve again! also check the rockers, some 07 Z06s reported a problem with the rocker arms. there is a sticky about it in this section.

infanterene

Sorry about your motor. Did your car make a ticking sound? I just noticed my 2007 making a ticking sound with 28000 miles.

'06 Quicksilver Z06

Good luck with the repair.

70K is a good bit of mileage and I see that you just got the car a little while ago in March.

How many miles were on it when you purchased it, if you don't mind my asking?

Or in other words, how many miles did you manage to put on it before this unfortunate mishap?

Thanks

Jorday

If the spring itself is the problem, which has been suggested, then I think you could make a case that a spring change is the one and only thing that's going to help.
I just picked up my 09 up from Livernois after having their stage 3 heads installed on my car. My car was stock with 7k miles on it, and some very slight increased wear was noted on a couple of the guides. I asked what was going to be our plan regarding the valves/springs/guides for my heads. It was explained to me that the spring change was by far the most important aspect of the project. They didn't think bronze valve guides were needed for my heads and the stock guides were used on my heads. Finally, they recommended that I continue with the stock exhaust valves because changing to a solid stainless steel exhaust valve would be a downgrade thus could create more potential issues than it solved.

SmokinZ

So as you can see, there are many ideas for fixes, but nobody can give you a definitive path to follow. It's all about hedging your bets and taking the compromises you are most comfortable with.

kawaiilaosboy

I got the car with around 68,000 miles on her. I've driven her around 2k miles. I know it sucks to only have driven her just 2k miles. I really enjoyed her too.

What brand valve springs do you guys recommend for someone keeping the stock power?

Keith Tedford

Back in the '60s, the stock big block solid lifter Chevies were notorious for dropping valves when subjected to high rpm use. The engines would easily wind well past 7,000 rpm. What was happening was that the valve springs weren't strong enough to keep the valve in constant contact with the rest of the valve train at those revs. The valves would actually free fall shut rather than getting gradually set back down on the valve seat by the cam lobe contour. Eventually the keepers would get pounded right down through the retainer dropping the valve. Heavier valve springs were the cure for those problems. Of course broken valve springs can cause the same catastrophe. Just perhaps, we are seeing the same thing here? If this action is violent enough to pull the keepers through the retainers, perhaps it can be attributing to the heads being popped off any valves with problems from when they were made.