Cylinder Heads
The cylinder head sits on top of the engine block and contains the valves, valve seats and usually the camshafts. It forms the top of the combustion chamber and carries the inlet and exhaust ports, sealed by the head gasket below it.
What it does
The head seals against the block through the head gasket, containing combustion pressure. It houses the valvetrain that admits air and fuel and releases exhaust gas, and carries coolant passages that manage combustion heat.
Signs a cylinder head is failing
- White sweet-smelling exhaust smoke
- Coolant loss with no visible external leak
- Oil that has turned milky
- Bubbling in the expansion tank while the engine runs
- Overheating that returns after the cooling system has been checked
When to replace them
Not a scheduled item. Replaced after overheating distortion, cracking, or valve seat damage that cannot be machined out.
What to confirm before ordering
Have these ready and the counter can usually confirm the part in under a minute.
- Engine code from the block
- Whether the head is supplied bare or assembled with valves and cams
- Whether the head bolts are single-use and need replacing
- That the block face has been checked for flatness
Cylinder Heads questions
Does a new cylinder head come with valves fitted?
It depends on the line. Heads are supplied both bare and fully assembled. Confirm which you are getting, because the difference in bench time is significant.
Do head bolts need replacing?
On most modern engines yes. Torque-to-yield bolts stretch permanently when tightened and cannot reliably be reused. Order them with the head or gasket set.