Katech_Zach

It seems like all I do lately is answer PMs and emails about cylinder heads, valves and valve guides. Rather than type the same thing over and over I'm going to put some information down here. This isn't a debate, it's what we (Katech) know. Take the information if you wish.


1. Exhaust valves
THERE IS NOTHING WRONG WITH STOCK EXHAUST VALVES. Do not replace your lightweight hollow-stem sodium-filled exhaust valves unless the shop suggesting otherwise can provide valvetrain dynamics testing showing their combination is stable with the heavier valves. You may be doing more harm than good.

2. Rocker arms
THERE IS NOTHING WRONG WITH STOCK ROCKER ARMS. We have never failed one EVER. PERIOD. There was a small batch problem in 2007. If you have a 2007, buy new GM rocker arms. If you have any other year, forget about it. Do not buy "upgraded" trunnions. We have seen those fail.

3. Valve guides
We have seen high valve guide wear on both intake and exhaust valves on LS7 and LS9, but never once have seen valve failure from worn guides. If this concerns you, replace the stock guides with bronze. When doing so, you need to change the intake valves to Katech titanium/molybdenum valves because the molybdenum coating has better material compatibility with the bronze. These valves also have steel tip that eliminates the lash caps. We have been collecting data on valve guides and I've said before that we are going to publish a report, but at this point we don't know when. Our engineering department has been so busy with crunch time for the upcoming racing season and our increased business, this report has been on the back burner. What you read above in this paragraph is what we know and what you need to know. We don't know what the root cause of the wear is, but the fix is noted above.

That is all.

Short-Throw

This would be great to add to the C6 Z06 facts sticky -- that MAJ Z06 started years ago.

Thanks for the clarification!

GMuffley

This should relieve some of the paranoia.

Everett Ogilvie

In my haste I misunderstood one sentence the first time I read it, so to clarify you have seen upgraded trunnions fail, right? Sorry about that and thanks for the post.

Toxic-evo

I think he means he has seen the trunnions fail.

Katech_Zach

You are correct.

musicmankeb

What makes this so ironic though is that you guys deal with WCC and they want to do both 1 & 2 when you call them about getting heads done. So I think you guys should get on the same page?

Katech_Zach

No need to get on the same page. WCCH is a private company with no affiliation to Katech so they are entitled to their opinion. They port heads for us, but we dictate Katech-spec. As a cylinder head supplier, WCCH is not obligated to validate combinations which include camshafts that they do not supply or test. Katech on the other hand is an engine/vehicle builder which is obligated to validate packages that we sell.

jimbob8915

So please do tell why exhaust valves have failed in some low mileage motors. You have seen yourself excessive guide wear. What should be done to prevent it?

musicmankeb

Things would be so much easier if you guys did head work for all of us Hint hint!

Dirty Howie

Why don't the exhaust valves need replacing along with the intake valves if going to the bronze guides ??


DH

jimbob8915

I disagree! All he said is nothing wrong with GM parts an just replace them with GM or his expensive parts. They still see high wear an no real fix or explanation! Why did he even post anything until he has something conclusive other than potential customers are basically bugging him.

cruzin2

Sorry Jason, looks like there is no way to make people believe GM parts are ok.

Wulverine

Most of us just want to know what the weak link in the engine/valve train is so we can fix it before it creates a catastrophic failure. Exhaust valves have been the reported failure for far more engines than intake valves. What is causing the excessive valve guide wear and exhaust valve failure is what we want to know. Nothing More!

RedZ4me

Good info, may stop people from spending in areas not really needed. thanks Jason

Cheesecake 07

Appreciate the info, Jason.

Keyword. Pretty subjective. Im assuming your old enough to know that sometimes s*** happens. It's(valves breaking) clearly happening at such a low rate that nobody knows or won't disclose it. Either way if you search, you'll find it's not enough to lose sleep over. Just sayin...

C6 Mayhem

I'll be surprised if anyone, including Jason will ever be able to say with 100% certainty why some guides in LS7's and LS9's show more wear than other engines. Personally I think that nearly .600 lift, with a 5/16 valve stem, along with the possibility that some owners run these things at 1400-1600rpm in 6th gear, for extended periods under heavy load, could have something to do with it. Think about it..........low rpm, low volume of oil splashing on the valve stems, lean intake mixture, heavy load, and elevated coolant temp. Under those conditions that one and a half to two thousands clearance between the stem and the guide can disappear in a hurry. When that happens, any remaining oil gets cooked, the valve galls the guide, material transfers onto the stem, and the clearance opens up. Can't prove it.......just saying, seems plausible to me.

'06 Quicksilver Z06

Maybe there was a bad batch of exhaust valves.

OnPoint

Jason,

Thanks for posting. Most of us appreciate it.

Look forward to the full analysis report.

1stZ

I 2nd. Pls continue to provide whatever info you can & don't let the critics stop you from doing so. Can't make everyone happy.