Sinister04L

Say, to accommodate your QM600 cam?

z06king

I had mine upgraded over the winter. It was a stock '06 (built Oct '05) with almost 16k miles. I rarely get the RPMs over 5k, but a lot of the miles are on spirited drives through the canyon. I got new SS valves, rockers, dual springs, ti retainers, steel spring bases, seals, valve locks, Serdi -Multi- Angle valve job (all seat & valve work, includes bowl blending), and Dis-assemble, clean & re-assemble heads.

My car is out of warranty and I want to keep it around for many more miles and years, so I figure the relatively little money now was worth the peace of mind that I want with this car.

mirage2991

^why didn't you put on new valve guides? or were they ok?

tjwong

Ferrea doesn't make a hollow stem exhaust valve for the LS7, they only have the SuperAlloy valves for the LS7. However they will make what ever you want as a custom valve, but its going to cost you. The Super Alloy valves are about the best valve you can buy, it won't break. But its considerably heavier than stock, so a good valve spring is needed.

z06king

I don't know the answer to your question. I'm not a mechanic and I won't pretend to be an expert on the exhaust valve issue. I talked to 3-4 knowledgable people about the issue and decided to have the heads shipped to Charlie and Keith at RPM Motors. The work I had done was what they recommended.

mirage2991

So it's safe to say your heads where just fine at 20k. It's to bad they didn't give you a "report card" on your parts.

VetteVinnie

I thought the current working theory was that the guides were not the problem, but excess heat transfer from the sodium filled valves was causing excessive premature wear in some cases.

http://forums.corvetteforum.com/c6-z...-begins-3.html

niphilli2

Is the problem really any deeper than the valve spring itself? Have we seen failures where the spring is intact and the valve stem brakes?

I am very interested, thinking of going from a C5Z which I love to a C6Z next year. We have had issues with valve springs breaking (to be expected with an aggressive camshaft), but I belive that is the extent of the problem in the C5.

VetteVinnie

Read the thread I linked above. IMHO, yes, it's necessary.

mirage2991

there is one (maybe more) builder on this forum that uses those sodium filled valve in his race car with no problem.
Even then, if the guides are fine, then there isn't a problem of heat transfer, or at least it isn't related to mileage or daily usage. Which then, if it is related with racing, there's a whole lot more questions that needs to be answered, such as if the correct grade of oil was used, if it is related to oil starvation issues, was it tuned to lean etc etc...

then reading your link, and seing a set of head being worked yet no guides are changed begs to wornder...because in your link he said the valves were fine, the guides were not...might as well be flindfolded and start shooting in hope to hit a target...

0Myhardtop

Yes, the replacement springs will handle lifts of all of our cams (except Lucifer and Hell-Maker). You must specify otherwise.

Thanks,
Carlos

VetteVinnie

I know there's a lot to read, but this is the key piece of data driving my decision:

http://forums.corvetteforum.com/1574098856-post94.html

Originally Posted by Richard@WCCH
Given the same conditions, the bronze guides will wear as well. The size of the small heat path must be increased. With a solid stem valve heat is allowed to travel further up the length of the stem. It provides a larger flow path for heat dissipation.

The primary heat path is through the valve seat. The secondary heat path is through the valve guide. Lean stoic. conditions at cruising speeds generate lots of heat on the exhaust valves with unleaded fuels. The heat bakes the small amounts of oil that makes it to the lower portion of the exhaust guide. Once the lubrication is gone there is metal to metal contact and on a molecular level electron sharing occurs. The steel molecules of the exhaust valve stem have a greater resistance to wear. The powdered metal guides have mixture of wear resisting alloys along with lubricious properties pressed into the matrix. You don't have to beat on the engine to experience valve guide wear.

The primary reason we use bronze valve guides is because GM will not sell the guides separately. Rather they will sell you an entire replacement head. The aftermarket parts supply only furnishes bronze alloy valve guides. I personally like the powdered metal valve guides the factory uses but the supplier does not sell piece meal to the public. Additionally we have no long term wear issues with the bronze guides and solid stem stainless steel valves.

In the last decade GM has done a masterful job improving both metallurgy and rocker arm geometry to reduce overall valve guide wear. Rocker arm designs are also superbly executed. The issues seem to only be related to the sodium valves.

Hope this helps.

Richard

niphilli2

Interesting... Sodium filled exhaust valves have been around in the Z06 since '01 (I think, possibly '02). This is the first I have heard of this type of issue, but I am by no means 'in the know'.

mirage2991

I believe it was 2002. They were also on the LT4, and GM SBC fast burn heads.
They are also used on most Turbo applications.

racezx9

Hmmm sounds like FUD to get business to me. GM does have a warrenty on the engine for 100K.

BearZ06

and sometimes it doesn't pay even when everything is stock

kentz06

You should be more concerned about the cast pistons than the exhaust valves...

LGR

I would do new springs right away.

Mopar Jimmy

What's the best replacement valve spring to use on a stock LS7 engine, what is the replacment upgrade that most use w/out comprising and overtaxing the nice light weight valve train on our LS7 engines?

I know from past experieince you don't want to use to heavy of a valve spring and want a replacment spring be similar to the charateristics of the stock springs to keep the lightweight valve train in tact, etc.

What valve spring accomplishes this (or do most with stock LS7 engines just replace with stock LS7 springs (or is their a single valve spring that is more durable that still is extremely compatible with the lightweight features of the LS7 valvetrain?

C5 Frank

LOL

To OP... Seriously... you have 20k hard miles and you want to rebuild the top end?? To me that seems excessive. I understand that there have been some members that have had issues. But the C6 Z06 has had it's share of batch issues since day one. My car ( late '06 Z) had a bad intake valvespring.... yes it broke at 14k and I was lucky enough to shut the car down before any collateral damage occurred. There was the bad rockers in '07 bad trannies in '08 and I feel the valves could be just that... a few bad ones. I understand the paranoia that can hit when we read the posts of broken valves...
But how is replacing a light weight sodium filled valve with a one piece heavy valve going to wear over time. That could be even worse then the stock valves over time. I am not sure what the answer is, but if it makes you feel better... spend the money for the peice of mind. But IMO if you are seriously worried about it... maybe it is time for a different car!!!