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LS7 Heads

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  • LS7 Heads

    There are a large number of LS7 heads that are experiencing excessive valve guide wear, which if not corrected leads to dropped valves and destroyed engines. It appears that the problem is caused by very poor machining from the third party supplier that Chevrolet uses for the heads. The best description of the issues involved that I have found is here:

    On the Lingenfelter web site you have a page where you talk about porting, doing a 3 angle valve job, and “checking all tolerances” on customer supplied heads . But there is no mention of what you do when you find worn out valve guides.

    Could you please answer the following questions:
    1. When you replace a valve guide, what material is the valve guide made of? PM or Bronze or ? and why do you feel that is the best choice? What is the extra cost of doing this work?
    2. What machine equipment do you use in the machining of the valve guide and valve seat?
    3. After the valve guide and valve seat a machined, do you check them to verify that the concentricity of the value seat and guide are within specification?
    4. There seems to be small number of heads that have a second problem where the distance from the rocker pivot to the valve guide centerline is off by .050-in. Are you checking for this?

    I know these are some very detailed questions, but there are a large number of Z06 owners who have had their head fixed by other shops only to find out 10 to 20 thousand miles later that the valve guides are worn out again because the concentricity issues where not corrected.