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Originally Posted by cmitchell17
Interestingly enough, I am almost certain I never saw that warning when buying my heads, not sure if they had it up a year or so ago?
That being said, I think there is a pretty big conflict on interest here in them selling aftermarket castings. I've never seen a GM TSB or anything about seats "falling out" especially in stock applications.
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From what I have read the stock seats tend to have trouble with increased lift, lobe intensity, and seat pressure. They don't seem to be as problematic in stock applications.
Aside from that GM never acknowledged or issued a TSB for LS7's which were notorious for dropping valves even stock.
Pray, GPI, and TSP have all mentioned at one point that the stock seats are a issue in heads cam applications. Pray has even had a failure in one of his FBO bolt-on hi ram cars.
I also agree with Old man and Parish that valvetrain instability could of also been a player. Your springs might not of been shimmed correctly or incorrect lifter preload. Either way I am just pointing out that the stock seats are a weak point on factory castings.