Draft:Cylinder Head Shims
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Cylinder head shims are thin metal spacers installed between the cylinder head and the engine block in internal combustion engines. They are primarily used to adjust the compression ratio, restore proper engine geometry after machining, or accommodate performance modifications.
Function and Purpose
[edit]Cylinder head shims serve multiple functions in engine assembly and tuning:
- Compression ratio adjustment: Shims increase the clearance between the piston and cylinder head, thereby lowering the compression ratio. This adjustment is particularly useful in high-performance or forced induction engines to reduce the risk of pre-ignition and engine knock.[1]
- Compensating for resurfacing: During engine rebuilds, material is often machined from the head or block, altering original specifications. Shims help restore the factory deck height and combustion chamber volume.[2]
- Custom engine builds: In hybrid or modified engines, shims allow tuning of piston-to-head clearance and adjustment of combustion chamber geometry.
Materials and Construction
[edit]Cylinder head shims are commonly manufactured from stainless steel or multi-layer steel (MLS). Some designs use uncoated center layers with outer layers coated in materials like Viton, which improves heat resistance and sealing capabilities.[3]
Available in a variety of thicknesses—typically from 0.2 mm to 1.0 mm—these components must be precision-cut to ensure a proper seal and avoid warping or fluid leaks.
Installation and Considerations
[edit]Installation requires careful surface preparation, accurate torque procedures, and adherence to engine specifications. Improper installation can cause compression leaks, overheating, or gasket failure.[4]
In some engines, using a shim may alter camshaft timing due to changes in deck height. Adjustments to timing components may be necessary to preserve performance and engine balance.
Re-torqueing the head bolts after thermal cycling is often recommended.[5]
Applications
[edit]Cylinder head shims are used in a range of automotive and industrial applications, including:
- Racing and performance vehicles
- Turbocharged or supercharged engines
- Classic car restorations
- Engine overhauls following machining
In vintage vehicles, they are particularly useful for maintaining original compression ratios when OEM head gaskets or components are no longer available.[6]
See also
[edit]References
[edit]- ^ https://www.turbododge.com/threads/how-much-do-the-head-gasket-shims-lower-compression-by.93788/
- ^ "Cylinder Head Shims – Innovative Machine & Supply".
- ^ "Head Gaskets - Multi-Layer Protection". www.cometic.com.
- ^ https://www.acl.co.nz/wp-content/uploads/6-Cylinder-Head-Shims.pdf
- ^ https://www.scegaskets.com/wp-content/uploads/2014/02/Embossed-Shim-Steel-HG-Instructions.pdf
- ^ "Shim Gaskets for Classic Chevys: A How-To Guide". Northern Auto Parts.
External links
[edit]Categories
[edit]Category:Engine technology Category:Automotive engineering Category:Internal combustion engine components