A valve spring tester is normally used in the machine shop environment to check the condition of valve springs when rebuilding an engine or a cylinder head. Valve springs tend to loose their tension over the years and the only way to make sure they will perform correctly is to test them.
In performance and racing applications, valve spring open and closed pressure is one of the most important specs that need to be checked and adjusted during the initial engine build.
Valve springs in very high output race engines loose their tensions in as little as one run down a Quarter Mile drag strip. It is not at all unusual for racers in the professional categories to check and replace valve springs every run at the drag strip.
There are two main types of this tool.
The most commonly known bench type of tester is the Rimac Valve Spring Tester. It has been the industry standard for many years
and is a very dependable tester for bench use. The newer versions are available with digital readouts to make the testing easier.
There are also computer based spring testers that will record all of the valve spring pressures of a particular engine and save them into a software program in order to compare them after the engine has been run at the race track.
For the home mechanic there are also some tools available that work in a normal bench vise and use a hydraulic pressure gauge to measure the spring pressure. This type of tool is an economical option for enthusiasts.
Trackside or "on the engine" type
The other type of checker is designed to use while the engine is still assembled and even still in the car. This type of tester can be used to compare the valve spring pressure to shat it was during the initial engine build and will help determine if a spring is beginning to fail. This type of tester requires some “feel” to get repeatable results, but as long as the same person is using the tool, it is great for the purpose it was designed for ….. checking the springs on the engine in the car, at the track.