What might happen if you bend a valve stem?
Installing bent valves A bent valve stem will cause unilateral support of the valve seat on the seating ring. Consequence: The unilateral stress causes alternating bending stresses and fatigue fractures in the fillet radius at the transition to the stem.
Why do I need to replace my cylinder head seat?
Another reason to replace a seat is if a valve has broken because the seat is not concentric with the guide. Misalignment between the seat and guide causes the valve stem to flex every time the valve closes.
Where is the valve seat in the cylinder head?
The most critical sealing surface in the valve train assembly is between the face of the valve and its seat in the cylinder head when the valve is closed. Leakage between these surfaces reduces the engine’s compression and power and can lead to valve burning.
What causes a valve head to overheat during replacement?
The guide diameter has been dimensioned too small during replacement of the valve guides. Inadequate lubrication, stiffness and seizures of the valve stem in the guide. Consequential damage such as overheating of the valve head or seat area can occur. Old, worn valve cotters were used during replacement of the valves.
What are the problems with wide valve seats?
Wide seats cause the following problems: •Seating pressure drops as seat width increases. •Less force is available to crush carbon particles that stick to the seats. •Valves run cooler, allowing deposits to build up on them. The seat should contact the valve face 1/32˝ from the margin of the valve.
Another reason to replace a seat is if a valve has broken because the seat is not concentric with the guide. Misalignment between the seat and guide causes the valve stem to flex every time the valve closes.
Why are the valve seats on my car broken?
When a valve seat comes out of its counter-bore it shatters into many pieces from impact. Those pieces from the valve seat may enter the intake and/or exhaust manifolds as the result of normal air turbulence. The cylinder head for this engine originally uses PM (powder metal technology) valve seats with an approximate depth of .286″ (7.264 MM).
What to do with a broken cylinder head?
The debris found that re-entered the combustion chamber included particles of valve seat, piston/ring material from the original failure.” When a valve job is to be performed, it may be common procedure for the technician to just pull the intake and exhaust manifolds back to provide just enough room to get the cylinder head off of the engine.
What happens if the valve is too high on the seat?
If the area of contact is too low on the face (too far from the margin), the valve will ride too high on the seat. As the engine warms up and the valve expands, the contact point moves down the valve face away from the margin. The valve may lose partial contact with the seat causing it to lose compression and run hot.