The First 5mm Stem Stainless Steel Valves for the Tillotson 212R, 225RS and Predator Non-Hemi Cylinder Heads
The smaller valve stem saves weight over the 5.5mm valves stems. Less weight means more rpm with less spring pressure. There is also a potential for better flow by reducing the obstruction in the bowl and choke area of the port. The valves come nitrided on the top of the valve head and the stem to protect from heat and wear.
These Valves are +.050 Longer than stock valves to allow more lift without coil binding. This will change the spring pressure of the springs so you may need to add a .050" shim to the bottom of the spring to have proper spring pressure for lower lift cams.