A cylinder head is the engine component mounted on top of the engine block. It closes the top of the cylinders, helps form the combustion chamber, and provides a place for valves, ports, injectors or spark plugs, coolant passages, and oil passages.
For heavy-duty diesel replacement work, understanding the cylinder head is also useful for identification. Before a replacement quote, buyers should confirm the engine model, OEM number or casting reference, old-part photos, and whether they need a bare or complete cylinder head.
Quick Answer
A cylinder head seals the top of the engine block and helps control air intake, exhaust flow, combustion sealing, cooling, and valvetrain movement. It works with the head gasket, pistons, valves, injectors or spark plugs, and the engine block. The exact design depends on the engine family and application.
Where Is the Cylinder Head Located?
The cylinder head sits above the engine block. The head gasket is installed between the cylinder head and block to help seal combustion pressure, oil passages, and coolant passages.
Inline engines usually use one cylinder head. V-type engines usually use one cylinder head for each bank of cylinders. Some heavy-duty diesel engines use separate or modular head designs depending on the engine architecture.
What Does a Cylinder Head Do?
| Function | What It Means |
|---|---|
| Seals the combustion chamber | Helps contain compression and combustion pressure with the head gasket and block. |
| Controls air and exhaust flow | Intake and exhaust ports guide gases into and out of the cylinders. |
| Houses valvetrain components | Valves, springs, guides, seats, rocker components, or cam-related parts may be located in or around the head depending on design. |
| Supports fuel or ignition hardware | Diesel heads may include injector locations; gasoline heads may include spark plug locations. |
| Manages heat and lubrication | Coolant passages and oil galleries help control temperature and lubricate moving parts. |
Major Cylinder Head Components
Common cylinder head features can include:
- Intake ports and exhaust ports.
- Intake valves and exhaust valves.
- Valve seats and valve guides.
- Valve springs and retainers.
- Injector bores or spark plug holes.
- Coolant passages.
- Oil galleries.
- Head bolt or stud holes.
- Gasket sealing surface.
- Camshaft or rocker-related mounting points, depending on engine design.
Not every cylinder head has the same layout. The component arrangement depends on engine type, fuel system, valve design, and manufacturer design.
Cylinder Head, Head Gasket, and Engine Block
The cylinder head, head gasket, and engine block work as a sealing system. The block contains the cylinders and lower engine structure. The gasket seals the joint between the block and the head. The head closes the top of the cylinders and supports airflow, combustion, cooling, and valvetrain operation.
If this sealing system fails, symptoms may include coolant loss, oil contamination, compression loss, overheating, white exhaust smoke, or repeated gasket failure. These symptoms should be inspected before replacement decisions are made.
Why Cylinder Head Identification Matters
For replacement procurement, a cylinder head should not be selected by a general engine name alone. Buyers should check the OEM number, casting reference, engine model, engine serial or nameplate information when available, and photos of the old part.
This matters because similar engine families can have different cylinder head versions, configurations, or included components.
Bare vs Complete Cylinder Head Context
When sourcing a replacement, buyers may see bare, loaded, complete, or assembly wording. These terms describe configuration, not guaranteed fitment.
A bare cylinder head is usually requested when the rebuilder will install or reuse separate components. A complete cylinder head may include more installed parts, but exact included components vary by engine model and supplier configuration. For configuration details, see the Bare vs Complete Cylinder Head guide.
When To Move From Learning To Procurement
After identifying the component and confirming replacement may be needed, prepare the following information:
- OEM number or casting reference.
- Engine model and application.
- Engine serial or nameplate photo if available.
- Photos of the old cylinder head from multiple sides.
- Required configuration: bare, loaded, or complete.
- Quantity and destination.
For broad cylinder head and cylinder block sourcing, use the Cylinder Head OEM Replacement Parts Guide. For a Cummins 6BT / 6CT example, see the Cummins 6BT and 6CT cylinder head guide.
Request Identification Support
If you need help checking cylinder head compatibility, send the OEM number or casting reference, engine model, photos, required configuration, quantity, and destination through the Volgen contact page. Final compatibility, included components, commercial terms, and availability must be confirmed during quotation.
