I was wondering if you ever got your motor reassembled after dropping a valve seat a second time and how it ran? I have a 2008 impala 3.9 that I had the same thing happen, dropped valve seat cylinder #1 damaging head and top of piston car only had 101,000 miles. About to reassemble and just wanted to know if I should check anything else thanks

 

I have 2007 impala that drop a valve seat so I swapped the engine ran it about a year and it did it again . I'm wondering if anyone figured out what is causing it . thanks

 

OK sorry for the delay. life gets in the way.

I replaced the head the second time and trailered it to a friendly Chevy dealer who had been helping me from the start. He set it up on his diagnostic equipment for the initial start up. Nothing jumped out at him, but the throttle body sensors readings where not normal. He changed the complete throttle body assembly out and it's been good ever since. That's 20,000 miles later. My guess is the throttle body was causing an over lean condition and cylinder one runs hotter then the others and it caused the head to over expand letting the seat to loosen and drop.

Just a guess.
Pat

 

I never figured out what caused mine to drop out. Guy at machine shop where i took motor to said this isnt a common problem with these motors but he sees it alot with chrysler engines. Is your motor a 3.9 and how many miles did it have on it when the seat fell out?