Being our stroked 500 HP 1999 LS1 is 8 years old and still has the orginal valve springs and car is always driven hard if on the street or on the track it was time to see what the valve springs looked like and test some other types.

This test replaced only the springs and the sparkplugs.
We swapped the stock springs with those for a L92 which are a Behive design and no inner spring as the stock ones have.

We found just by looking that 2 of the stock springs were slightly shorter then the others and 4 of them where the inner spring were broken.

After springs and sparkplugs were swapped we did a short break-in testrun with our Ease scanner to see fuel trims at lower engine loads are richer then with the old springs so we assume a few valves from the weak stock springs just had too much age and were not totally shutting the valve causing a leaner fuel conditions.

The engine idled smoother and the engine seemed to pull to higher gears faster.
We'll drive the car for awhile with these L92 springs and then next test will be with 918 springs which are 1/8th inch taller then the L92 which was 1/8th inch taller then stock ones.