Ford Focus Forum, Ford Focus ST Forum, Ford Focus RS Forum - View Single Post - POssibly buying, looking for advice.
View Single Post
Old 01-18-2013, 11:21 PM   #20
DTC P0606
BC_ZX3's Avatar
Join Date: Jul 2007
Fan#: 48751
Location: Vancouver, BC, Canada
What I Drive: 2001 Red ZX3 Turbo

Posts: 3,309
Points 2,439, Level 29
Points: 2,439, Level: 29 Points: 2,439, Level: 29 Points: 2,439, Level: 29
Level Up 93% Completed
Level up: 93% Level up: 93% Level up: 93%
Forum Activity 11%
Activity: 11% Activity: 11% Activity: 11%
FF Reputation: 98 BC_ZX3 Excellent Standing Member
Buy-Sell-Trade Rating: (3)
Originally Posted by Russo2 View Post
What exactly is it on the valve that fails?
The valve itself doesn't fail; the valve seat insert fails. The valve seat insert separates from the cylinder head within the combustion chamber and gets trapped between the moving piston and top of the combustion chamber with disasterous results.

"Soft" aluminum heads have hardened circular valve seat inserts - to withstand the "hammering" of the valve rapidly opening and closing - embedded into the head. They are usually held in place by a simple interference fit; the seat fits tightly into a counterbore machined in the head.

So any valve seat repairs require head removal and complete head dismantling (cam(s) off, valves and springs out) with some machining involved.

edit: amc49 beat me to it.
BC_ZX3 is offline  
    Reply With Quote