Cylinder Head Bolts
| Standard | ISO 898-1 · OEM Standard |
|---|---|
| Material | SCM435 / 35CrMo / 42CrMo |
| Strength Grade | 10.9 / 12.9 |
| Size Range | M8-M14 |
| Surface Treatment | Phosphate / Black Oxide |
01
Product Description
Product Description & Key Specifications
Cylinder head bolts clamp the cylinder head, gasket and engine block under high preload while the joint sees combustion pressure, thermal cycling and vibration. They are normally controlled by an OEM engine drawing because length, shank design, thread engagement, bearing face and tightening sequence affect gasket sealing and long-term clamp load.
This range covers SCM435, 35CrMo and 42CrMo cylinder head bolts in grades 10.9 and 12.9, with common M8-M14 sizes for passenger cars, commercial vehicles, hybrid engines and industrial engine assemblies. ISO 898-1 may define the mechanical property class, while the final dimensions and tightening method are usually specified by the vehicle or engine manufacturer.
Phosphate and black oxide finishes are used where controlled assembly condition, low coating build and compatibility with engine installation procedures are required. For torque-angle or torque-to-yield programs, reuse policy, lubrication condition, washer face and certificate requirements should be confirmed before production.
| Product type | OEM cylinder head bolts / engine head bolts |
|---|---|
| Standard basis | OEM drawing / ISO 898-1 mechanical properties where applicable |
| Material | SCM435 / 35CrMo / 42CrMo alloy steel |
| Strength grade | 10.9 / 12.9 |
| Size range | M8-M14 |
| Common models | M8 x 80, M10 x 100, M11 x 120, M12 x 140, M14 x 160 by drawing |
| Thread type | Metric coarse or fine thread, full thread or long shank by OEM design |
| Head and bearing style | Hex flange, 12-point, internal drive, washer-face or separate washer design by drawing |
| Surface finish | Phosphate / black oxide / oiled finish |
| Tightening method | Torque, torque-angle or torque-to-yield sequence confirmed by engine specification |
| Documentation | MTC, heat treatment record, hardness, tensile, dimensional report, PPAP support on request |
02
Selection
Selection Advantages by Application
Automotive Engine Head Assemblies
M8-M14 10.9 / 12.9 cylinder head bolts are used for engine block and head clamping where gasket sealing and controlled preload are critical.
Automotive and EV fastenersHybrid and Range-Extender Powertrains
SCM435, 35CrMo and 42CrMo head bolts can support hybrid engine programs when OEM geometry, tightening sequence and certificate requirements are defined.
EV and hybrid fastenersIndustrial Engines and Generator Sets
Drawing-based cylinder head bolts are suitable for selected industrial engine and generator maintenance programs where material traceability and dimensional reports are required.
Industrial equipment fasteners03
Assembly
Recommended Matching Products
04
Manufacturing
Manufacturing & Quality Control
Manufacturing CapabilityQuality Control
OEM drawing review for head style, bolt length, shank form and thread engagementSCM435 / 35CrMo / 42CrMo material verification and heat number traceability
Cold heading, forging and machining route selected for long bolt geometryStraightness, overall length, shank diameter and bearing face inspection
Quench and temper heat treatment for 10.9 / 12.9 performanceHardness, tensile and metallurgical checks according to inspection plan
Thread rolling and controlled washer-face or flange-seat finishingThread gauge, pitch, thread length and surface defect inspection
Phosphate or black oxide finishing with protective oil and project packagingCoating appearance, dimensional report, MTC, CoC and PPAP support on request
05
FAQ
Common Questions Before RFQ
Are cylinder head bolts the same as standard hex bolts?
No. Cylinder head bolts are engine-specific fasteners with controlled length, shank, bearing face, thread and tightening requirements. They should be produced to the OEM drawing.
Can you supply torque-to-yield or torque-angle cylinder head bolts?
Yes, production can follow an OEM torque-angle or torque-to-yield design when the drawing, material, heat treatment and acceptance criteria are provided.
Should cylinder head bolts be reused?
Reuse depends on the engine maker procedure. Torque-to-yield or torque-angle head bolts are often replaced after removal unless the OEM service specification says otherwise.
Which material is used for head bolts?
Typical materials include SCM435, 35CrMo and 42CrMo alloy steel, selected according to strength grade, bolt length, heat treatment route and OEM requirement.
What is the difference between phosphate and black oxide finish?
Both are low-build finishes used on many engine fasteners. Phosphate is often selected for assembly condition and oil retention, while black oxide is used where the drawing specifies it.
What RFQ information is needed?
Provide the drawing, engine model or bolt part number, size, material, grade, head style, surface finish, tightening method, quantity and required certificates.
Need OEM cylinder head bolts for an engine program?
Send the drawing, bolt length, thread, head style, material, grade, surface finish, torque-angle or torque-to-yield requirement, quantity and certificate needs. We can review production feasibility and quote a traceable supply plan.
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