ospreycorvette

Not the valves being weak, it is the guides, either an oil problem (not enough oil to the guides) or some alignment issue. Yes GM knows but are keeping quiet for a reason.
Do you think GM would do a recall on the 27000, with no good fix or ride it out.

They will ride it out, much cheaper.

67redrat

Guides have very little to no oil for lubrication, if they did the engine will use oil, that can't be allowed with today's environment. Guides use a valve guide seal which prevent oil from entering the combustion chamber. Think of it like this all other ls engines with exception to the ls9 don't have this issue. The ls7 has higher lift can, and 1.8 ratio rocker you all do the math.

mirage2991

just because the engineer used a 1.8 ratio doesn't mean it's bad. You can use less aggressive lobes at the cam end, slowing down the lifter and pushrod, then with the higher ratio you can accelerate it. You have to remember the engine only care about what the valve is doing, not the lifter or cam (far as performance). The old shchool ZL-1 had 580 lift with a 1.7 ratio for comparison, we have 591. So your idea that it is the problem is wrong. You will find out there's alot of LS1-2-3-6 running way more aggressive lobes with way more ramp speed than the stock LS7 without any issues what so ever...and with well over 600 lift too boot... You can also check other threads were guys have 30+ events, over 50k miles and they are running strong with no issues...and there's at least an equal amount of those guys as to those that exploted their motors.
Now, introduce the possibility that something went wrong with the casting of a batch of heads, or its machining, or its parts (guides/valves) and it wasn't "caught" (could be impossible to know if it's a part flaw during its manufacturing) then you end up with issues like theses where on one hand, you get exploded motors and on the other, you have happy motors with a bunch of miles and a bunch of track days. That my friends, is the more plausible thing to believe.

67redrat

You are so wright, but I have never seen an aggressive lift with a large ration with non roller tip, just never seen one built. Bad casting very possible. But with all these engine kind of doubtful. Any how when my warranty runs out, I'll be installing full roller rockets, if my guides are good that is. If not the heads will be off and reworked with bronze guides and full rollers. I've never seen a failure with full rollers on aggressive cam and rocker profiles, none in any engine I've built anyway.

2000FRCZ19

55000 miles.

mirage2991

roller tip isn't really necessary, alot of time, the roller tip of the rocker doesn't even turn like one would think it would... the ZL-1 from GM back in the days has stamped rockers on a 1.7 ratio...and with canted valves...
With all these engines? there aren't that many, I think there's still under 15...it seems alot because the topic is beaten over the heads and the same blown motors get to be seen in every single one of them...shoot might not even been a casting problem...I think some bad guides made there way to some motors...
and to see if your guides are good or bad the heads have to come out ...changing rockers won't do squat if there's a geometry problem...but I'm pretty sure bad geometry isn't it, if it was, Katech and the likes would be running modified parts, and they are not.
(unless you are replacing them due to the needle bearing issue)

Mopar Jimmy

Very well put and makes a lot of sense.

The only thing I disagree with is there is closer to 50 documented failures of LS7 engines here (between stock and moddified LS7 engines).

The 10 MILLION dollar question is how many of all the 27,000+ C6 Z06s that have been built to date, will blow up b/f they have 80,000 miles on them? Until then, time will tell and then what really sucks is we will never really know!

LS9Drew

WCCH does recommend doing a rocker mod to the stockers $400ish (I dont remember exactly what he said it was though lol). He did say it was only an issue on some but he would do it just to be on the safe side

Greenstealth

I'm certainly no expert on this but I think the problem is a quality control issue with the guides that is magnified by the the amount of heat those sodium valves send up into the stem/guide. I spoke with Richard from wcch a few weeks ago and he seemed to agree. He also recommended going to a SS valve with a slighly heavier spring on the exhaust side (on top of the bronze guides). I will most likely be sending him my heads come winter time (which seems to be rapidly approaching).

1972bluelt1

Just bought a 07 Z06 with 7000 miles. Going to do a comp cams trunnoin upgrade. Plan to drive it 1-2 k/yr. Can't know how the car was driven the 1st 6600 miles. But it will never be driven on a track and probably never see red line. Rather not tear into the motor unless I really have to. I have 2 LS1s one with 91000, one with 9800. Had I know about these issues, I would have passed on the Z06.

Bill Dearborn

A trunion upgrade will not address the valve drop issue. However, while doing that job you can check the valve guides and see if you need to go further. Actual valve drops are far fewer than the number of people who find loose guides. Although the popular rework of the heads seems to be addressing the problem in the short term the question remains whether or not fixing the guides is the correct long term solution. It takes a fair amount of operation for the valve drop problem to occur. I dropped a valve on my 08 at almost 23K miles with about 4K miles of track use. Others I know about have been in the range of 15K to 25K miles. Given most owners average less than 6K miles per year a recurrence may not show up for 4 or more years after the heads have been reworked.

However, as the saying goes you go with what you know now, pay your dues and take your chances.

Bill