I own a 2007 Z06 with 25k miles on it. I belong to a Facebook C6 technical forum and am constantly reading posts regarding 'having the heads and valves done' as well as harmonic balancer issues with the LS7 motor. Can anyone tell me why so many are concerned with the heads and valves on this motor? What are they talking about when they say these things should be 'done'? My Vette is 100% stock and I couldn't be happier with it. Runs perfectly and based on published factory specs regarding the parts which have been used to build this motor why would anyone mess with it? I 'drive' the car but don't abuse it. Just looking for some honest input as to why so many people are concerned with the heads/valves and harmonic balancer. Thanx y'all!

 

Google is your friend. Hundreds of threads on the topic.

 

Both of these issues tend to attract lively discussions here.

This is a link to one of hundreds of threads about the balancer. Short version is that it's possible they separate and cause damage. The telltale sign is a "wobble" and possibly some chirping. My LS3 has 114k miles and still has the factory balancer with no wobble. I'm getting it replaced only because the front crank seal needs replacing.
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https://www.corvetteforum.com/forums...verstated.html

I don't own an LS7. But here's a link to a bunch of discussions about it. The issue has to do with a design flaw in the heads which could lead valve damage and catastrophic engine damage:

site:corvetteforum.com ls7 heads problem

 

Short version, some of the LS7 heads did not have the valve seats tram/concentric to the center line of the valve guides, and this caused the valve head to crack off as they are trying to seat to seats not tram.concentric to them. Hence matching was off, since it cut the seats, reamed the guide channels first, then guides where installed afterwards that caused the problem with seats not concentric to guides.

The second problem, is actual wear to the valve guides and the sodium valves, on on a motor that is rev'g to 7K rpms, which too can cause the vavles to try to close to the seat not tram as well, and again snap the heads off the valves, to drop valve head into cylinder, to take the engine out as well.

So either way, common upgrade to the LS7, is to replace sodium filled valves with solid stronger SS valves, either replace if over sized for new valves or ream the guides to fit the shafts of the new valves correctly, then re-cut the valve seats using the center line of the valve guides to make sure valves seats are concentric valves in the guides.

And while on a roll, understand that the intake manifold on the LS7, does not flow well enough to allow the engine to pull hard to 7K in the first place (just not enough room under the hood). Hence stock motor pulls hard to about 5.8K, then you can ring the motor toto 7K, but is not really gaining any horse power instead.
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So the easy trick to really get the LS7 to pull hard to 7K gaining HP all the way to over come the problems on the restrictive flow intake manifold, is super charger making about 5lbs of pressure. Hence On the above dyno graft, put a ruler on the HP line from idle to 5.8K, then on that ruler line, continue the line to 7k, to really see what the motor can do when it can breath correctly all the way to red line. With long tube headers and high flow cats, 5lbs of boost, engine is making 650-700HP gaining HP all the way to red line, but the better one, is with the displacement of the motor and boost from say a TVS blower, the amount of torque that the motor makes just off idle to about 5Krpms, is freight train special that can break the tires any gear at will.

Maggie Heat beat super charger on stock LS7 with conservative tune, including stock exhaust manifolds and stock cam, and no meth kit to push the timing even more to gain eve more power, with it making about 650hp at the crank.

 

There are literally hundreds of threads/posts on this forum concerning the LS7 heads & the multitude of "fixes" that owners have done, do your own homework & use the search feature here for hours of reading

 

I also have an LS7. Mine has 13,000 miles and runs perfectly. Reading about these valve issue makes me uneasy so I read a lot about it. It seems if you aren't pushing the car hard and running at high RPMs it's not an issue. I'll probably have the heads done at sone point just for peace of mind but for now I'm leaving it alone.

 

This probably belongs in the Z06 area. That way we can hash the issue out agin for the 3,426th time.