Rebuilt head exhaust valve failure in 27k miles?

Hi,

like the title says, on my 2011 Ford Escape 2.5L with 163k, my usual shop sent out my head for rebuild 27k miles ago.

Now it has P0301. A second shop found that one exhaust valve is down to .0015 inch clearance, the spec is .010 to .013 inch. These are the bucket tappet style.

• How is that kind of wear possible?
• Cyl 1 PASSES the leakdown test. Does that mean it's worth spending the $1,000 on a valve adjustment?
• Am I back at another head replacement again?

The head work has a 24k 2 year warranty on it, so I'm out of luck on that.

There is a whole huge saga about how I left it at the original shop for two months and they never figured it out, they replaced the coil. Then I took it to the Ford dealer, they did the same misdiagnosis and replaced the same coil again, and broke a sparkplug then saying they are stuck in the head (after 27k miles).

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Thanks