COMP Cams Tools 4716 Most high performance engines today require the use of larger-than-stock diameter valve springs. This 1.320" Spring Seat Cutter for installing larger springs and hardened spring seats on GM Vortec Heads will allow the engine builder to machine the cylinder head to the proper size for your spring. Each cutter requires the use of an arbor/pilot, which are available in three different sizes. Spring Seat Cutter for GM Vortec - 1.320" Spring Seat O.D., .630" Guide O.D. COMP Cams 1.320" Spring Seat Cutter for Vortec Heads, .630" Guide COMP Cams Spring Seat Cutter For Gm Vor