ls7 valve guide problem only existed around 2006?

[void_kp]

Not that you should believe any youtuber, but this guy made a video in 2022 claiming that a "top engineer" in GM clarified the problem on LS7 was only on a very limited batch of engines.



this seems to be pretty recent and I'm curious to hear if there has been any other claim in recent years from a reliable source

[Gbland60]

All I’m gonna say about this subject which has been talked about for years is guide wear is a known issue on LS/7 and along that improper valve train set up will lead to catastrophic engine failure .
If you wanna know more FACTS on the subject from ACTUAL OWNERS not some GM Rep jump over to the C6ZO/6 Corvette Forum. Those guys over there are not in denial on this matter. Most are pissed off
Good luck and enjoy your Z/28 I know I do ����

[highrevving]

I recently saw this, 2007 C6Z06.

[joelster]

Some day I'll make a short but sweet video of my findings on my own LS7, and my years of digging for factual (scientific and backed up measurements) of LS7 engines, and my association with reputable (but want to remain anonymous for fear of internet bashing) shops. If you own a 2006-2010 LS7 engine, stop and have it looked at. Z/28 owners, and '11-'13 Z06 owners, carry on lol.

Here's my take:

The engineering and the blue prints for the LS7 are poetry in motion, and they work flawlessly. The problem arises from lack of QC from certain vendors, mainly the place that did the machining of the cylinder heads. There is NOTHING wrong with the valve guides. The valve guides are simply the first wearable part that will show exaggerated wear. To give you an analogy that makes sense, it would be like watching your front tires burn the outer edges down to the cords. Would you say "these tires are junk, I'm going to replace them with better tires!". Guess what would happen to the new set of tires? It's the same thing with the guides. Sure, there's shops that will say the material is suspect, and you can change them with something better, but fixing the misalignment would be a better course of action.

Any shop that says "All LS7 heads are junk!", also (coincidentally) have a 1-mouse-click-payment solution to get your heads fixed with their in-house cnc program, cam specs, tuning, and labor. Seems rather convenient.

As for my own findings, I was alarmed at the amount of preload that GM runs on the lifters from the factory. Then alarmed that they advise owners to drain the 5w30 and run 10w30 at the track. You never ever ever want the oiling side of the valvetrain to overpower the spring side of the valvetrain. really bad stuff happens when you do that. Go on YouTube and watch some of these big bad LS7 engines that have heads/cam done that put 600rwhp (on the happy dyno) down, yet nose right the **** over at 6700rpm, and ask yourself why is that? At 7k, they are done like dinner. Mine peaked at 588.13 at 6740rpm, and was making 587.98 at 7k and 578.32 at 6k. I don't have a huge cam, but I have real good springs, proper pushrods, and very little preload. If something should happen and my engine experiences some valve float, there's virtually no way for a piston to smack a valve. I'm running .030".

Anyways, rant over lol.

[macalot]

Thanks for your grounded input, much appreciated.

[Gbland60]

The guide wearing is due to the valve guides, not being concentric to the seat, which was done by an outsourcing company which in turn if you don’t get your valve guides replaced and have your seats re-cut You will have exaggerated guide wear. Also I wouldn’t use my old valves if you have excessive guide wear .
I don’t have the energy or the time to sit down and comment on every single perspective on this issue as my head hurts just thinking about it not to mention the rod wear. I still have my old original head’s completely intact in a box on a shelf with 20k miles of mostly normal driving and my intakes guides are worn out just a couple of exh . I see you have lingenfelter heads . What does their head package consist of ? I maybe should of went with those instead of AHP

[Michaelh007]

Another big problem is the weight of the stock exhaust valve. Obviously the preference is lighter valvetrain but even when they switched head manufactures, they didn't fix the overall design of the ls7 head so many of the problems remain.

Had my set of heads that were replaced at 17k miles for warranty work recently removed (@41k miles) as I got a ported and milled set installed when I added a cam.

Even bare bone oem heads have some wear and tear at earlier mileages. I attached a video of my heads disassembled a few weeks ago.

https://www.youtube.com/shorts/8UaDZ8IeQPw

[void_kp]

Originally Posted by joelster

If you own a 2006-2010 LS7 engine, stop and have it looked at. Z/28 owners, and '11-'13 Z06 owners, carry on lol.

this aligns very well with my own (small) research and also from my (limited) knowledge of how engine operates
But yes, it's an interesting topic because over the years everybody wrote anything and the opposite too... so it's a very "noisy" set of datapoints with VERY limited respectable sources that reported about it.
Z06 are not Z/28, LS7 are not all equal (manufacturing year is an important factor). I will still probably buy a different head for peace of mind, but I am also building confidence on the fact that this is not going to happen on a 2015 z/28.

[joelster]

The best thread that I've read about the LS7 heads was when a Lockheed Aerospace engineer bought a Z06, noticed excessive wear, and then built a tool to accurately measure whether a head was machined properly.

I found a decent thread you will find interesting.

https://www.corvetteactioncenter.com...-engine18.html

[SIM GhostrdrZ]

Originally Posted by joelster

Some day I'll make a short but sweet video of my findings on my own LS7, and my years of digging for factual (scientific and backed up measurements) of LS7 engines, and my association with reputable (but want to remain anonymous for fear of internet bashing) shops. If you own a 2006-2010 LS7 engine, stop and have it looked at. Z/28 owners, and '11-'13 Z06 owners, carry on lol.

Here's my take:

The engineering and the blue prints for the LS7 are poetry in motion, and they work flawlessly. The problem arises from lack of QC from certain vendors, mainly the place that did the machining of the cylinder heads. There is NOTHING wrong with the valve guides. The valve guides are simply the first wearable part that will show exaggerated wear. To give you an analogy that makes sense, it would be like watching your front tires burn the outer edges down to the cords. Would you say "these tires are junk, I'm going to replace them with better tires!". Guess what would happen to the new set of tires? It's the same thing with the guides. Sure, there's shops that will say the material is suspect, and you can change them with something better, but fixing the misalignment would be a better course of action.

Any shop that says "All LS7 heads are junk!", also (coincidentally) have a 1-mouse-click-payment solution to get your heads fixed with their in-house cnc program, cam specs, tuning, and labor. Seems rather convenient.

As for my own findings, I was alarmed at the amount of preload that GM runs on the lifters from the factory. Then alarmed that they advise owners to drain the 5w30 and run 10w30 at the track. You never ever ever want the oiling side of the valvetrain to overpower the spring side of the valvetrain. really bad stuff happens when you do that. Go on YouTube and watch some of these big bad LS7 engines that have heads/cam done that put 600rwhp (on the happy dyno) down, yet nose right the **** over at 6700rpm, and ask yourself why is that? At 7k, they are done like dinner. Mine peaked at 588.13 at 6740rpm, and was making 587.98 at 7k and 578.32 at 6k. I don't have a huge cam, but I have real good springs, proper pushrods, and very little preload. If something should happen and my engine experiences some valve float, there's virtually no way for a piston to smack a valve. I'm running .030".

Anyways, rant over lol.

Your rants are top notch, rather than just trashing the LS7/Z28.
You might have more up to date info but the last I read GM says 15W-50 oil for track use.

[CountingZs]

Stumbled across this C6 Z06 review the other day by Savage Geese, which is not quite a year old: https://youtu.be/Op8LEDchcKY

At about 15:53, they featured some of the lead engineers on the LS7 team responding to the valve guide issue. I am not picking a side here, but some may find it interesting.

At the end of the day, I think joelster hit the nail on the head:

Originally Posted by joelster

The engineering and the blue prints for the LS7 are poetry in motion, and they work flawlessly.

Quality control is the Achilles heel of most great products.

[joelster]

I think those guys are slightly coached into what to say lol. Wait until they are retired for 15+ years and then ask them the question again lol. The valve train is a much bigger problem than that guy made it sound like, and when they fail, they tend to fail in spectacular fashion, not just make some clattering noises.

My friend Justin is on his 3rd LS7. I bought his blown up block. It snapped a valve head off, damaged the sleeve, and put a 2mm crack into the water jacket. Thankfully for me, I have a world class racing machine shop 10 minutes away, and the owner looked at the block and said "no problem, I've fixed way worse". When it's done I'll have a back up block in case I want to go bigger cube down the road.

[JAFWF]

A question, why aren't people using LS9 heads?

[joelster]

Originally Posted by JAFWF

A question, why aren't people using LS9 heads?

Try finding a set. I don't know if they are better, worse, or the same, but I do know that they are extremely rare. Most LS9 cars are museum pieces anyway.