CHEVROLET LS1. PAC-1204X RPM Series Dual Spring set of 16.
Premium quality Japanese spring steel wound in USA by PAC. Made with advanced heat treatment processing and surface finishing techniques (nano peening) to extend fatigue life.
High spring frequency to allow for better spring surge control at high rpm.

145lb at 1.800″ installed height.
385lb at 0.650″ valve lift.
Coil bind (spring solid height) 1.000″.

RET135-16 is the matching Titanium retainer.