Katech_Zach

This C6 Z06 came into the shop after 21000mi and an estimate 10 hours of hardcore track day use. It is a great data point to see how the valve guides are doing.

The heads were done by WCCH to Katech's spec with CHE bronze guides, Katech Ti/Mo intake valves and new OEM exhaust valves.

The vehicle is equipped with a Torquer 110 cam, PSI 1511 springs, Katech Ti retainers, OEM lifters, and OEM rocker arms.

The customer has driven it 21,000 miles including a rough estimate of 10 hours on road courses doing HPDEs. He was concerned/curious how the guides were doing after all this and brought the car back to us for cylinder head removal and valve guide measurements. Cylinder heads were torn down to find virtually no valve guide wear. We are simply installing fresh springs/retainers, reassembling and installing back on the car.





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~STOLEN~

thats good news!!!
can you provide any valvetrain info like cam specs, springs used, pushrod length,lifters and rocker set up.

thanks

Katech_Zach

Thank you for reminding me. I meant to include that. Edited.

~STOLEN~

thanks, and even better seeing those tolerances after 22k miles with oem rockers/lifters

Katech_Zach

OEM rockers/lifters are perfectly fine. I think even more important to note is that it's had a Torquer 110 cam the whole time. Higher lift than stock and the valve guides are still okay.

Dan_the_C5_Man

Alright Jason, I'll bite.. So, what do we think about running the Mo coated Ti intakes with PM or MS90 guides?

Will the coating hold up against that material? Or is this a case of not enough data to make a definitive statement?

What did the surface of the intakes look like in these heads?

Thanks Jason.

ConfusedGarage

A few things to note, the rockers and lifters are original and both now have 38,000 miles (it was noted that they were OEM but not that they were original).

Additionally, because I daily drove this car from May - Oct in Michigan for at least 3 seasons with the refreshed heads, I have a lot of cold starts in temps of 20-30 degree range. I see a lot of people fussing about oil temps in regards to the heads on these cars, but the data from my car and my usage shows no correlation there (granted it is a sample of 1 but consistent with how many on here use their cars).

Lastly, just remembering now that I probably have 40 1/4 mi passes on these heads too now that I think about it (car has gone 10.8 and trapped 133 on a day with decent temps).

Katech_Zach

I don't see the purpose. The point of using PM or MS90 guides is so you can re-use the OEM intake valves rather than purchasing the Ti/Mo valves. If you're going to buy the Ti/Mo intake valves why not just go with the proven bronze. Bronze guides cost is not very significant compared to the cost of the valves.


I don't know. We've never tested with it. I would have engineering take a look at the hardness and surface finish. If that were okay I would like to see a 30 hour durability test on our Spintron. Again, why invest in that when Ti/Mo and bronze are proven?

Do you mean the surface finish of the intake valve stem?

Dan_the_C5_Man

Yes, intake valve stem finish.

And there is a point.. We are seeing excessive wear / durability issues on the CrN coating of OEM valves.. So, what if we have a set of heads already re-worked with PM guides, and we swap to Ti Mo to avoid the CrN surface roughness / durability issues? Are the stem diameters materially different between the Ti Mo and OEM intakes?

Katech_Zach

Understood. To feel confident in Ti/Mo with PM or MS90 I would want to see a 30hr Spintron durability test.

The Ti/Mo intake valve stems looked so good you might be able to pass them off as brand new.

Stem diameter on the Ti/Mo is stock.

Dan_the_C5_Man

Thanks Jason.

Apocolipse

As mentioned, here is the CrN failure mode of a tumble-polished stock Ti intake valve. While polishing helps extend guide life, a lack of lubrication is causing the coating to fail. This is where the TiMo valves come into play as the Molly coat gives the valve the required lubricity. Id be curious if cutting little slits into the valve stem seals on the intakes would help them live for those of us that have already "fixed" heads.

Ultimately - this thread is proof that the intake valves with coated molly are the answer.

Dirty Howie

DH

rio95

I’m confused. Those clearances are tighter than what Richard told me he sets them at. Aren’t those super tight?

MTPZ06

73DBG

Yup...

only one valve even registered in thousandths 😳

interesting....imagine if we’d have known this 10-12 years ago, could have saved a ton of LS7’s jihading themselves🤔
and a **** ton of money to the owners....

SSMOKE

I hear that. Unfortunately, I am in the process of replacing the replacement heads I bought in 2009, that have 14,300 miles.

AzDave47

Jason, another data point, my guides 10K miles after WCCH head work, your TiMo intake valves, new OEM exhaust valves and K501 cam with 1511 springs and Ti retainers. They were checked while I got the bottom end forged. Quite a bit of time at 4-7K+ RPM and a few track days. Heads were checked and measured at WCCH.

Apocolipse

Pretty well proves that the main failure mode of the fixed ls7 heads is due to a lack of lubrication.

Dan_the_C5_Man

This and the scribbled out numbers caught my eye as well. Seems like one too many decimal places..