Yes, I have seen this happen. I once met a guy who had a seat drop out while
the car was idling in his driveway. From my understanding, the original brass
seats heat and expand at a different rate than the aluminum cylinder head. The
seats are "staked" to help keep them in, but they can still drop out. When I
had my head done we switched to steel seats, as I guess they tend to expand and
contract at a rate more consistent to aluminum (?) and last longer than the
brass... at least that is my understanding. Look at the under side of the head,
and you will see the stake marks around the seats... look like little round
pock marks.
Greg Burrows
-- "C. Halsted" <chalsted@adelphia.net> wrote:
has anyone ever dropped a seat in a U20 head? a local fellow just pulled the
head off his 2L and one of the valves is open and seat has obviously moved
and looks to be the reason the valve is open... is this something that
happens over time? he said he was driving it around the neighborhood, came
home and shut it off, and next time he started it it ran like
crap...couldn't even get it to rev... checked compression and #3 was Zero.
pulled the head and observed the seat. I have pix I could e-mail if that
would help in diagnosis. thanks for any input!
Craig Halsted
roadsters mostly
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