The all new TSP Gen 5 LT1/L83/L86 .660" spring kit featuring PAC valve springs and PRC integrated seat/seal is the newest offering in valve spring technology offering the latest processes and material for maximum spring life. PAC Racing is a leader in valve spring technology, so it was only natural to team up with the best in the valve spring industry for our latest offering in a valve spring kit! The dual valve springs used in this kit feature a proprietary spring that was developed specifically for the Gen 5 6.2L LT1 engine that requires a taller installed height than the typical LS engine. These are NOT the same springs used in our LS dual valve spring kits, but they do use the same technology and polishing technique that is exclusive to PAC Racing valve springs! We have developed a .660" dual spring kit with the help of PAC Racing that still offers excellent valvetrain control, even for the more aggressive hydraulic roller camshafts. These valve springs will offer excellent durability and stability and will work well with factory-style lifters. PAC uses a proprietary process called nano-peening that increases the residual stress of the wire, meaning that it compresses the molecules together very tight to help the molecular bond hold better. This greatly reduces the chances of spring fatigue and failure. Our kit also includes the patent-pending Precision Race Components integrated valve seat and seal that makes for a very easy installation without any possibility of mis-installation or tearing of the valve seal!