PT-200 Valve Spring Tester Articles and Tutorials 

Does it hurt to bind a valve spring on the tester?

Here's an interesting test to do on a brand new valve spring (thanks a lot to Joe Lepone who was the first one to show this to me on the first PT-200 valve spring tester prototype when we were both a lot younger):

1) Turn auto mode off on the tester so it will use the same installed height for every spring measurement

2) Set the installed height correctly for the valve spring (just move the handle on the tester until you are at the desired height and then hit the Space bar on the keyboard to lock that height in).

3) Compress the handle on the PT-200 tester to carefully measure the spring.

4) Now hit the 2 key on the PT-200 tester to go to the next spring location so we can make a comparison measurement.

5) Before measuring, compress and release the handle on the tester to take the valve spring all the way firmly down to coil bind several times.

6) Hit the C key on the tester to clear out the coil bind data, and then do a final measurement on the spring.

Now by hitting the 1 key and then the 2 key you'll be able to see the difference in the seat pressures at the same installed height, with the first measurement done before the spring was taken to coil bind and the second done after the spring was taken to coil bind.

You typically will see a significant difference in the seat pressure between the two measurements. The difference will vary depending on the spring type, but its not atypical to see a loss of as much as 10 lbs on the spring after it has been taken to coil bind.

Some engine builders feel that this is clear evidence that taking a valve spring to coil bind during the testing process damages it.

Is this true?

I believe that in some special applications where the spring is not run in a RPM or lift range where it is highly stressed that the opinion is true (more on this later).

However, for the vast majority of valve springs used in racing applications, the engine is run in a range where the spring is being pushed to the upper range of its performance limit. This means that it is being run close to the minimum allowed coil bind clearance and also that the engine RPM is high enough so that spring harmonics come into play.

When the valve spring is run in this condition, even though it has some coil bind clearance, due to the rapid motion of the valve and the resulting spring harmonics, the coils will repeatedly be going into a "local bind" condition, where the coils go through a sequence of individually coming in contact with each other.

You can confirm this by watching a video of a racing valve spring in action, such as this one from Pac Springs:

Pac Springs High Speed Valve Spring Video

Note that the spring harmonics cause the spring coils to move up and down in a wave motion and that because of this harmonic motion the spring coils come in contact with each other in what I like to call a "local bind" condition.

Thus once the spring is being used at racing RPM, the coils repeated get put in a "local bind" condition, and thus once run, the spring effectively gets taken to coil bind during operation.

I believe this is one of the significant reasons why you typically will see an immediate loss in the seat pressure of new springs the first time an engine is run at its racing RPM range.

In addition, I feel you can reduce this seat pressure loss by binding the springs prior to performing the final measurement process, as it puts the springs through the same binding process that is going to occur anyway when the springs are run at racing RPM.

Thus I feel for the typical racing valve spring, you are better off binding the spring a few times on the tester before making the final measurement, as it will then provide you with a more accurate installed height that will result in less pressure loss when the engine is then run at racing RPM.

The only case where I think binding the springs can cause more harm than good is in some applications such as "pure stock" racing, where spring is not installed close to the minimum bind range and the intake system of the engine limits the RPM that the engine can attain. In that case the spring may not endure any significant "local bind" conditions and thus the spring may not see the typical "first run" pressure loss that occurs with racing springs. In this case if obtaining the highest possible seat pressure is important and no spring shimming is allowed, it may be best not to bind the valve springs on the tester.

Paul Titchener, Power Technology

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