HyperX

A buddy of mine is contemplating getting SS exhaust valves in his Z06. He lives in Canada and the shop that will be doing his work told him to stick with the OEM guides - but his heads will be done by Texas Speed Shop. Is this a good idea? or is there a real reason to go with bronze guides with SS exhaust valves?

erick_e

If the guides are worn he will need to have them replaced, and as I understand the OEM guides cannot be sourced by anyone other than LPE. Which is why most are using bronze guides.

EX1

Simply replacing the exhaust valves doesn't solve the problem. I switched out my valves when I did my cam swap, drove 15k miles and then had WCCH check my heads. My OEM guides were trashed they said. He needs bronze guides.

jedblanks

Another question is, does simply replacing the guides work.

We fault the stock valves but any valve will break if the guide is worn enough. Is this a mis-machined or poorly wearing guide or do the OEM valves cause it.

erick_e

Disclaimer. This is my opinion.

I think the answer is yes, it does. I base this off my analysis from reading thousands of threads on this matter, and the GM statement that there was an error in machining the guides. I deduced that in replacing the guides, the original machining error has been eliminated.

clogan

My opinion: I think it is more prudent to replace everything you can - valves, guides, springs, especially. The LS7 cylinder heads from GM come with such poor quality control that, in some estimates, up to 90% have flaws that will cause a valve drop before reaching 50,000 miles. The OEM heads are so bad that dealers ought to be offering a head R&R option at time of purchase. That way, they could roll it straight off the showroom floor into the service department, and have the heads replaced, and just get it over with.

jedblanks

I just fear the SS crowd will be revisiting this again in 20-30k possibly due to other issues caused by the extra weight of the valves. Plus I don't want the extra noise associated with heavier valves and/or springs. It may, however, be a good idea to buy new oem valves to get the "later" version, in case there is a difference.

azZ06Mike

Well if there is any fear from running ss valves then every 20,000 miles check the springs. I run heavier duty springs which make up for the difference. If you run stock springs with ss valves you might have an issue. But i highly doubt that the average weekend racer will put enough high rpm stress on these motors to have an issue.

A good racer who does alot of track event should have enough common sense to check wear parts during the year and know when to replace things.

Mopar Jimmy

The consensus with the experts like WCCH, Katech, etc., is to use new bronze valve guides if going with SS valves, so it seems FOOLISH for your friend not to do this.

jedblanks

Assuming I've decided to go with bronze guides, I understand some are better than others. Should I use particular ones?

Jawnathin

I've heard CHEs are the ones to get. I think thats what WCCH uses.

H82BFST

How many miles on the stock guides when you put in SS valves? ANd did you check the guides when you put in SS valves?

Mark2009

Yes and yes.

ConfusedGarage

Seems ridiculous to stick with the OEM guides as anyone who has changed over to bronze done by a shop that we know does it right, WCCH, has a 100% success rate with either valve, OEM or SS. The success rate with the oem guide, not so good. 100% was a no brainer for me and most. Note how there isn't a valve bulletin from GM, its a guide bulletin.

HyperX

Right but the guides affect hollow two piece valves, and since no Ss valves dropped, I am really not sure you need copper guides, especially if his are in spec.

arkus

I think just replacing the valve guides with bronze guides will solve the problem .
I say this based on reading many many threads here .If you want to go further you could also replace exhaust valves using
molybdenum , titanium or stock valves.

The problem is the valve guides.

'06 Quicksilver Z06

While I certainly don't doubt WCCH's success with bronze guides and the stock OEM exhaust valves, does anyone in here know how many cars in here or out there have this particular setup?

I ask because I know that WCCH does the heads for Katech Z06s found to have worn guides.

There are about 60 Katech Z06s and not even all of them are running heads set up with bronze guides and stock exhaust valves.

I know of about 5 cars in here running this setup. Do you know of others?

In contrast, I have found approximately 155 cars in here running bronze guides solid stemmed stainless.

Many done by WCCH. No reported failures.

So while I believe you that WCCH has had no falires either way, both sample sizes are small, and the WCCH stock exhaust valve bronze guide sample seemingly by far to be the smaller sample of the two "variants".

So in the interest of full disclosure from here in, I think it important to point out that even with the WCCH SS valve setups, we're dealing with a small sample size, but an even considerably smaller sample if we're talking about WCCH heads in here using a stock exhaust valve setup.

While both show considerable promise, and no failures have been reported, one should probably take into account the number of cars running these, and really any other setups, when making a decision.

I agree with you on the guides as I believe in the case of Scuba_steve, I'd have to look at the case again, but I believe that be was running the stock valves in OEM guides, in a set of rebuilt heads.

But when you really think about it, any "cam only" setup in here, which dropped a valve, was by definition, running the stock exhaust valves in OEM guides.

In fact, any car which failed an exaust valve in here with untouched heads, was running the stock OEM exhaust valves in stock guides.

adamgl

My heads were ported by WCCH in 2009. Switched to Solid Stainless exh. valves. But didn't change the guides back then.
I'll have my heads off in a few days, so we can see what they look like after 10K - 15K miles. (Don't know exactly b'c all this happened before I owned the car)
Still haven't decided on whether I should send them back to WCCH for bronze guides or get PRC heads.
To answer the original question I would pick bronze over stock guides.

Mark2009

Neither number means anything, other than 60/65 and 155 cars have not failed. I'm sure there are over 15,500 cars with original guides and valves that have not failed. That is a huge number. Does that mean anything?

Of course not.

The only thing that will mean anything is when we eventually discover the root cause of the failure. In the meantime, everyone can only proceed as they think best, after weighing all the pertinent information available. Nobody really expects a solid stainless valve valvetrain to have the same failure mode that we are seeing with hollow sodium valvetrains, but there is no doubt that there are some possible failure modes with solid stainless valvetrains that would not be likely with hollow sodium valvetrains... failure modes that may not present themselves for thousands or tens of thousands of miles, or perhaps never for mildly driven cars.

You pays your money, you takes your choice (and your risks).

Visited with a local cylinder head machinist today, we had an interesting chat about the LS7 valvetrain. He was aware of some issues, but was not on the cutting edge of info like we are. One of the possible causes he mentioned, along with harmonics (KLJ is smiling), was geometry. Imagine that
.

Mark2009

On topic, there is likely nothing intrinsically wrong with the OEM guide. At least one very respected forum vendor is on record thinking they are fine. Now how they are installed or machined, or perhaps if they are a little short, is another matter.

There may be a very slight chance that their thermal conductivity is somewhat lacking, but since we don't have that spec we simply don't know. However, for this chance to be valid we'd have to conclude that the GM engineers didn't know what they were doing, and on a specification as simple as this I think there is very little chance of that, unless real world operation varied significantly from testing (and given our knowledge of test mules, little chance of that as well).