The ZL1 Speed Shop has spent a lot of time and effort to test and analyze different types of valves. The quality of steel alloy the valve is made from, the quality chrome on stem, the hardness of the tip, the finish on the seat face, the gram weight of the valve, etc are all criteria the ZL1 Speed Shop monitors and tests. We test valves by running them on our Superflow dyno for several days and then we remove the valves from the heads and measure and visually inspect them. We have learned what type or brand of valve can be trusted and what application is appropriate for each. Whether you need an inconel exhaust valve for a heavy boost or nitrous application or marine application or a light weight hollow stem valve or titanium valve for a high RPM application utilizing lighter valve spring pressures, the ZL1 Speed Shop can help you purchase the correct valves based on your type of head, engine compression ratio, guide allow, spring pressure,etc. Contact us to discuss the best valve for your engine and intended use. Single valves are available, call or e-mail to order single valves.