MTIRC6Z

"debating if exhaust valve upgrade is necessary on a street only daily driven vehicle"

UPGRADE? So you're gunna increase the weight of the exhaust valve by 30% (if you replace with SS) and decreasing it's ability to dissipate heat...sounds a lot like a DOWNgrade to me. The weight penality can be avoided if you replace the stock exhaust valves with titanium, but then you might want to ask youself why GM didn't do that while they were doing the intakes in titanium???

For the record I've got 14,000 miles on my MTI Stage II extreme.

Cheers, Paul.

1.8t

^ You understand that they make valvesprings that can EASILY control the added weight right? And from what research we have thus far, it looks like the stock valves ability to dissipate heat through the guide is too much for the guide, causing extremely excessive wear.

So, 30% more weight with a decreased ability to dissipate heat versus a more fragile valve and severe guide fatigue. Pick your poison.

Sinister04L

Have you seen a lot of guide wear in the heads you have pulled?

MTIRC6Z

"Pick your poison"...agreed. And while there are certainly springs that can handle the extra weight there's more to it than just that...when there's over 200,000 SS exhaust valves running around out there in LS7s we'll get a better idea of what all the other problems may be...there are no free lunches.

And personally, I've picked my poison. I'm going with the opinion of guys like Katech and MTI, guys who have loads of racing experience, and not the guys on the internet who are convinced the LS7 is a piece of crap built with cheap parts, or vendors who prey on "the sky is falling" sentiments to make a few extra bucks.

Cheers, Paul.

1.8t

My research about guide fatigue and the theory as to why its happening came from Richard @ WCCH and findings from very knowledgable owners on this forum who have had failures and an analysis done.

FWIW, WCCH is who Jason@Katech used to port his heads. If Katech can trust this shop for their work, I can certainly trust them for their experience/knowledge.

VetteVinnie

Cammed with stock valves here. Not too much track time (other than some 1/4 mile passes and a few 60-130 passes), but plenty of aggressive street driving.

Car has 14K miles on it now. I bought it with 5K and modded it shortly thereafter (CAI, headers, 160 deg T-stat). Cam went in about 3K miles ago.

Only problem I am having at the moment is oil consumption (white smoke). I am suspecting valve seals. I hope it isn't guide wear, or else it's a ticking time bomb. No matter. It's on the roster to get back to Ragin Racin for some head work at some point, in which case the I hope the oil consumption and white smoke mystery will reveal its source.

Rosspbig

If the motor is already going to be apart, it seems like it would be a good time to put upgraded valves in. If nothing else it would be great for peace of mind. They are not that expensive anyways.

6Speeder

I'm in agreement that it's a downgrade. I'm running a big cam, have for 18,000 miles with stock valves. Aggressive street and many, many drag strip passes.

EXCELR8

Upgrade!!!!!!!!!!!!!!!!!!!!
43,000 miles, cam, headers, 557 RWHP, to the strip a few times, mostly street driven. Sucked an exhaust value 3 weeks ago under normal driving, engine is gone. Have a new crate motor coming with titanium values. The exhaust values are problematic, if you are on the fence upgrade!!!!!

Lawdogg

Yeah, but are they good enough for Corvette Racing ALMS motors?

camaross621

I am also debating valves next weekend my cam goes in.. but I decided not to swing my car to 8000 RPMS like most of the guys dropping valves are doing. my limiter is set at 7200 and its not moving at all. shooting for 725/700 cam and bottle. my car has 5700 miles and is rarely driven during the week. .

jgaches

[QUOTE=MTIRC6Z;1574027841
UPGRADE? So you're gunna increase the weight of the exhaust valve by 30% (if you replace with SS) and decreasing it's ability to dissipate heat...sounds a lot like a DOWNgrade to me. The weight penality can be avoided if you replace the stock exhaust valves with titanium, but then you might want to ask youself why GM didn't do that while they were doing the intakes in titanium???

For the record I've got 14,000 miles on my MTI Stage II extreme.

Cheers, Paul.[/QUOTE]

I see people talke about the increase in weight but how much heavier is the SS exhaust replacement compaired to the stock intake? I assume not significant enough to worry about?

SS MPSTR

Is the exhaust valve issue common? Sounds extremely isolated to me.