A valve-spring compressor is used to compress a valve spring in the cylinder head while the valve-retaining cotters are removed. It is clamped over the top of the spring-retaining cap and underneath the cylinder head.

Without a proper compressor, there is a risk of the cotters being fired out at speed and lost, or causing injury. Some compressors have a G-clamp screw, others a cam-and-lever action. Check in a service manual for your make of car for the best type to use.

Guides that use

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