LS7 Valve Issue
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.
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.
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
Humor me here, but if its the machining issue like GM says it is where the seat and guide are not machined concentric to one another, wouldn't the friction from the side loading of the valve cause excess heat as well?
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Verdad Gallardo 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.
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.
Thread Starter
Joined: Sep 2004
Posts: 2,013
Likes: 85
From: Hicksville MN!
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.
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.
The side loading could be accentuated by the longer valve and higher ratio rockers. Just a thought...
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.
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.
How did you check concentricity?
How did you check geometry?
Staging Lane
Joined: Jan 2004
Posts: 93
Likes: 0
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.
Teching In
Joined: Dec 2012
Posts: 4
Likes: 0
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.
I believe the only way to disprove the GM theory is to spec a new set of heads...confirm concentricity and guides within tolerance....then put some miles on them and remeasure! you want to convince the sceptics...do this and report your findings! otherwise you and the less then a handfull of so called head gurus are just tossing theory and not data around.
