MTIRC6Z

While it's great to know what the 'fix' is I remain unconvinced that 27,000 Z06s require the fix...thus to some degree we're still in the dark.

If the conclusion is that ever single Z06 out there will eventually blow up because of this issue, then I think GM has a MAJOR problem on their hands, which seems unlikely.

Cheers, Paul.

JetBlue427

So basically my understanding is the stock exhaust valves are fine as long as you dont get excessive guide wear...when that happens then the valve is prone to snapping at the stem?

Katech_Zach

Yes which will be posted soon.

That I don't know. I'll try to find out.

Hirohawa

Thank you Jason for adding some sanity back to this discussion.

Z06 forum has been in disarray for a few months.

Sad thing is that there will still be the usual 4 or 5 "pros" and the 3 non owner trolls that will still discredit Katech's findings.

Truth is rarely as exciting as fiction, rumors, or conspiracy theories. But yet here we are.

Jawnathin

Thanks Jason. This group is a tough one and I do believe Katech has been unfairly criticized due to the association with the GM. I never understood how it could be argued that you're covering up for them despite you acknowledging valve wear and recommending bronze guides for the fix.

Yes, would love to know more about how to identify/explain/demonstrate a potential issue since not every car seems to be having trouble. You did say we'll know soon enough and mentioned 'excessive valve train noise' but given all the various ticking the motor does, I find it difficult to know what is excessive versus normal.

I know this was recommended for street cars, but for a car that may be tracked or driven hard, is your recommendation to use the bronze guides with Ti/Mo intake valves and OEM exhaust valves? Even for cars that don't have 'excessive valve train noise' or have been identified as having potential issues? Or do you feel that cars which don't demonstrate an issue to be fine?

I believe it is well understood that when cammed or tuned, the chance of failure seems to rise. Are the bronze guides with Ti/Mo intake valves and OEM exhaust valves still the appropriate solution for such modified vehicles?

I'm undecided on how to move forward, but I am open to the possibilities of tracking the car with minor bolt ons, a mild cam, and a tune. Knowing what we know today, that seems to be the death sentence for an LS7. I'm trying to figure out what I need to do to accomplish that goal reliably.

Appreciate your thoughts and feedback.

Random84

IBSSISTEVSIKTAA

(in before someone says "it's still the exhaust valves, stupid! I've known this all along!")


I think it's pretty clear now that Katech_Jason is suggesting a move away from OEM sintered guides. Period.

They use the coated titanium intake valves to maintain low mass while allowing two dissimilar materials to work well together for a long life; but there is no issue with the OEM sodium-filled valves, thus these are not necessary to replace.

Polishing the OEM intake valves is an inexpensive way to reduce the wear with bronze guides, but without the outright purchase of coated Ti valves.

In short, it appears that the valve guides are the sole issue in the eyes of Katech.

Katech_Zach

For a track car my recommendation is bronze guides. For a cammed street car it's good, but possibly not necessary if they are not worn and you will learn more about this in the upcoming statement from GM.

Turbosixx

Thank you Jason for this. Looking forward to reading.

speedmon

BUT.......

Doing the head work and replacing the guides is all about managing risk of failure.
And if the exhaust valve is suspected to be one of the failure points why not eliminate the risk during the head work.

I know I would feel VERY stupid if I did $4K (parts and labor) of headwork and left the hollow valves in there only to experience a subsequent failure.

Then I might have to buy a $13K motor+head work with SS valves (because I would be smarter then).

Unless you're not paying for it, its difficult to compare the increamental cost of the SS valves ($200) to the risk of buying a new engine and doing more head work ($15K).

Jawnathin

Thanks Jason. It sounds like you covered this, but just to be 100% clear, what about a 'cammed/tuned track car'? Is that just a bad idea altogether or are the bronze guides sufficient in mitigating valve train issues in that configuration?

Wow, an upcoming statement from GM. Thats news on its own. I'd love to see that.

Dirty Howie

Jason

Can you explain why GM jsut doesn't put bronze guides in? Surely you have advised them that this is the solution to the many motors they have and will continue to replace?


DH

Random84

There are no guarantees in life - besides death - and a forum member recently had his heads reworked with guides and SS valves, then promptly spun a bearing.

I think the message here is that the "problem" is likely going to boil down to inconsistent valve guides; with the broken exhaust valves themselves being a byproduct of this issue. Thus, proper guides = no increased risk of valve breakage.

Could you still blow a motor? Sure, but the odds should be significantly lower once the valve guides are replaced - at least, that's my expectation given what's been posted the last few days.

I also eagerly await a statement from GM.

Jawnathin

My concern with SS valves is the their weight and their effect on the rest of the valve train. I know you can run more aggressive springs, but I wonder what other mess can come from that. GM with went these sodium filled exhaust valves for a reason.

I'd love a solution that matches the OE valve weight while increasing reliability or making this a none issue. If the problem is with the OE guides (not valves) and the bronze valves w/ OE valves is a fix, that seems like the perfect solution.

Dirty Howie

Jason

Oil consumption is easy to quantify.

Would it be possible for you to post up a couple of vids. One showing acceptable valve train noise and one in which you believe it is excessive. Does it have to have an obvious bad lifter knocking sound or something less obtrussive ???????

Your wording seems to imply that there will soon be something coming from GM ?????????????????

Thanks for you help !!!!!!!!!!


DH

Dirty Howie

This is much too simple and direct of a solution

I wonder who will provide this service first ???


DH

Jawnathin

That seems like a reasonable and cost effective solution, but it still wouldn't address any intake guide wear that is been seen on the OE setups. Its not nearly as bad as the exhaust side, but its worth noting.

I'm thinking it just makes sense to get it all taken care of in one fell swoop.

Undy

I'm betting it's the machining that was defective, not incorrect (sintered iron) guide material. I further suspect that installing new sintered iron guides with the PROPER clearances will give the longevity one would expect and still SAFELY retain the non-coated Ti stock valve.

speedmon

There are no guarantees in life ...... I agree, therefore its about managing risk....spinning a bearing is a different issue.

The question is "Who would spend $4K on headwork and leave a known risk of failure in the engine". Not me. Murphy's law dictates that the valves have to be replaced.

I sure GM will be managing their risk as well.

Katech_Zach

Then why do we do it?

How do you know the solid stainless steel valves are not doing more harm than good?


For a cammed track car I would do bronze guides with ti/mo intake valves. That is the fix.

Because it's not necessary for a production car. It's QC problem, not a design problem. The GM statement will explain.

Yes.

If I had a car here with excessive valvetrain noise to take a video of I would.

20psirabbit

I have another question for you Jason just out of curiosity. I understand the explanation for using the Ti/Mo intake valves, why aren't the exhaust valves coated in Molybdenum when the change is made to bronze valve guides?