Originally Posted by KCS

So now it's heat?

Originally Posted by Katech_Jason

Look at the date on that email, April 2011. I was giving my thoughts at the time in a private email. Notice I used the words "I think". I wouldn't not have posted that on the forum because we did not have concrete data to back it up. We know now based on the statement from GM that is is a machining issue.

Originally Posted by z0sicktanner

the valve is getting to hot. the valve starts to wear the guide from heat. then the valve stem will start to coke or cook the oil on the stem. once this happens it's downhill fast and the wear speeds up. once the guide gets .0080 it will gall the stems. this is like a sand paper effect on the stem and at this point it's just a matter of time till it stresses the valve stem and it will snap off at the sonic weld everytime. but if you ever take one of these heads apart you will see the cooked on oil all the way up the stem. also you can take a valve seal off the guides and you will see a rainbow effect. again this is heat. the valve was not a good choice for this engine. and it's wearing guides at a very fast rate. wish Richard would post. he will tell you the same. it's heat. thats why so many vendors are using the ss exhaust valve now with bronze valve guides. also tumble polish your ti intake valves. there is a coating on the ti that wont work well with bronze

Originally Posted by Whistler

If you want to discuss the LS7 valve issues that's fine (albeit beaten to death)but please refrain from personal attacks!

Originally Posted by z0sicktanner

it's not in the tune it's the valve ..but high EGT or Exhaust gas temperature will speed up the wear in tuned cars yes. again points back to heat

Originally Posted by KCS

Are you saying the sodium filled exhaust valve just simply can't handle the heat of a stock LS7?

Originally Posted by ramairws6

You got it...

Originally Posted by KCS

To me, it seems like the machining issue is the more likely culprit. I'm not disagreeing that heat is playing a role, but its hard to believe a stock engine is overheating a sodium filled valve. Now if the guide and seat are not concentric like they say, I can definitely see a side loading issue causing enough excess friction and heat to wear the guides.

Have you cut a valvejob in any of your scrap LS7 heads you've posted on YouTube? Seeing how the seat comes in would be pretty revealing.

Originally Posted by KCS

To me, it seems like the machining issue is the more likely culprit. I'm not disagreeing that heat is playing a role, but its hard to believe a stock engine is overheating a sodium filled valve. Now if the guide and seat are not concentric like they say, I can definitely see a side loading issue causing enough excess friction and heat to wear the guides.

Have you cut a valvejob in any of your scrap LS7 heads you've posted on YouTube? Seeing how the seat comes in would be pretty revealing.

Originally Posted by Whistler

The side loading could be accentuated by the longer valve and higher ratio rockers. Just a thought...

Originally Posted by z0sicktanner

all the heads i see the guides are wearing from top to bottom or up an down. not side to side. i've checked valve seat concentricity. valve geometry ect. thats not the problem. it's the valve.

Originally Posted by z0sicktanner

for conentricity I check for run out using a valve seat run out gauge, you can get a pushrod lenth checker, and do a wipe test on the valve tops. The ideal contact point is slightly before the centerline on the intake side when the valve is closed and slightly after on the exhaust side when the valve is open. this is the way i do it.

Originally Posted by z0sicktanner

for conentricity I check for run out using a valve seat run out gauge, you can get a pushrod lenth checker, and do a wipe test on the valve tops. The ideal contact point is slightly before the centerline on the intake side when the valve is closed and slightly after on the exhaust side when the valve is open. this is the way i do it.