Product Review

Important Notice：
Pneumatic operated valve holder designed for 14mm and 18mm diameter spark plug holes, commonly found on all LS engine platforms.
The other end is a 1/4" female NPT which can easily be connected to air hose quick connect fittings. 14mm is the standard spark plug size for most all domestic and foreign vehicles. Actual part may vary from picture.

This tool is used when installing valve springs while the cylinder head is installed on the engine.
This tool allows the combustion chamber/cylinder to be filled with compressed air, which holds the valve closed while the valve spring is exchanged.
Simply place the cylinder you are working on at top dead center, thread the tool into the spark plug hole, and fill the cylinder with compressed air.
Just be sure to maintain the air pressure within the cylinder while performing the spring change.