Snowwolfe

Seen this on the ZL1 forum. True? I havent heard it before but am a recent new LT4 owner.

Apparently the Lt4 and Lt5 are having valve guide wear similar to the LS7. This info is from the Katech news letter.
"In an effort to stay continually innovate and stay ahead of the pack, we started tracking every LT4/LT5 cylinder head that came into the shop. What we discovered was a valve guide problem similar to the GM LS7 Engine. While it is unknown how many of these engines experience early wear, we saw enough based on our Race Shop inspections and CNC/cylinder head services that we wanted to come up with a solution. And we did."


“We inspect every engine that comes into our Race Shop, and so we began recording detailed clearances of valve guide wear of every set of LT4 or LT5 heads that we saw, and over the past year the numbers prompted us to develop and offer a solution.”

The problem and solution is similar to that identified by Katech several years ago with the GM LS7 engine.

“At this point, we’re not sure how far reaching this issue is or if it is of the magnitude of the LS7s valve guide wear,” said Suits. “But we’re in front of it and our solution will allow our customers to avoid putting other engine components at risk in the event a valve or guide failed.”

Owners of vehicles with LT4/LT5 engines can mail in their cylinder heads to receive the Valve/Guide Package, or can drop off the entire vehicle to get the update and take advantage of one of Katech's Engine Stage Packages offered in conjunction with the update at a discounted rate.

need-for-speed

mnl119

If this were so, why haven't we seen engines windowing the block like in the LS7? The LT4 has been out for almost 6 years now and I've not heard of one dropping a valve. Quite a different story with the LS7 where engine failures were seen in the first 2 years.

Bill Dearborn

Actually, the LS7 problems didn't start to be seen in any great numbers until 2011. There were some vague rumors in 2010 (5 years) but a fair number of people dropped valves in 2011 and 2012. So about the same time frame from first starting to hear about the problems until they started showing up on a regular basis on tracked engines.

Bill

Track

So...what’s their big plan to fix it? It’s not like a valve guid is high tech. Perhaps the plan is to wear into our wallets??

mnl119

Respectfully Bill, I recall a different timeline. I don't want to start a flame war but I remember hearing anecdotal evidence of dropped valves/detonated LS7's as early as 2008-2009 when I was researching buying one. This is the first time I've heard of similar problems with the LT4.

Here's a thread from a different forum that contains a post about a dropped valve from 2008, not just an out of spec guide.

http://www.digitalcorvettes.com/thre...oblems.132068/

I'm sure you're more familiar with this than I, but here's a list with dropped valve failures going all the way back to late 2005:

https://www.corvetteforum.com/forums...st-update.html

badhabit_wb

I dropped a valve last year in my 15z. I posted on the forum about it several times but I didn't check the guides. I don't think the guides had anything to do with me dropping a valve because I had a broken spring. The engine got replaced under warranty so I didn't check any further.

mnl119

Fair enough.

Maybe I'm just paranoid because I got out of my 2006 z06 due to paranoia on this issue. Could have had the heads fixed by AHP or someone else, but decided to go with something newer.

Tonylmiller

I have not heard much either, but the C7 ZO6 population are probably still under warranty, mostly.

andreas g.

I had 2 C6’s Z. I had 2 forged motors built for my 09Z. The heads were CNC
ported and the one thing we put in were
CHE bronze silicon valve guides. After 35,000 miles I pulled the heads and guess what, no valve guide wear. So I now have a new set of LT 4 heads for my modded 16 Z. 49000 miles so I figured it was time. They will be ported with new SS steel exhaust valves, comp conical springs and of course CHE bronze silicon guides. They last and it will cure any valve guide issues.

Bill Dearborn

I know about the list I think my engine is on the list. However, during the early years there weren't many reports just a few here and there with not much impact on people. Then in 2010 reports started coming along about limiting revs to preserve the valve train, followed by a surge of dropped valves on the track. Where most of occurrences happened. You may notice the list shows broken valve springs, spun bearings, oil starvation, etc for the early failures. Broken valve springs have been with us for years and come and go with production lots. The problem that raised it's ugly head in the 2011/2012 time period was broken off exhaust valve heads. With aftermarket shops coming up with all sorts of fixes for the problem. Katech was one of the first companies to announce a fix sometime in 2011. Thoughts about the cause were the weak sodium filled hollow valve stem, misaligned guides, etc. Fixes were bronze guides, stock intake valve and stainless steel exhaust valve with heavier valve springs or bronze guides with Ti/Mo intake and exhaust valves (the Cadillac of fixes). GM even announced there was a short production run of LS7 heads that had been machined improperly in early 2011.

If things like the LS7 issue are going to start happening it is just about the right time for engines with 15K to 25K and some serious track miles to start dropping valve heads.

Bill

mnl119

Let's hope that's not the case.

Tonylmiller

Good news is, there are some Z06s is out there with pretty high miles without known issues like this. I just sold my car with almost 28,000 miles and it pulls like a freight train.

silverbird

I'll be watching this.
I moved into a 2019 Camaro ZL1 last year after selling my 2002 C5 Z06.
Back in the day, I had Katech swap out the valve springs in my LS6 as a precaution and peace of mind.
The springs were an issue on 2002 and 2003 Z06's.
I do know my Camaro LT4 isn't hand built like Corvette LT4's.
Still, this has my interest and I'll be following this thread.
Silverbird

need-for-speed

Hand built would not matter. It's all about the components they use.

silverbird

This is true.
I'm pretty sure all LS7s were hand built.

RegnaR

I figured all LT4s are hand-built.

I thought I escaped the valve drop paranoia.

Tonylmiller

I would consider a complex assembly like a "hand - built" engine to have considerably more quality issues than a mass - produced one. There are many good reasons why complex assemblies are not hand - built these days.

need-for-speed

"Hand built" is propaganda.
The components / design is what matters.

Mr. Gizmo

hopefully this issue on lt4 and lt5’s is unfounded propaganda and is just a ploy for the aftermarket tuners to drum up a little business.