Does anyone have the part number for the MP Viton valve stem seals for my '67 273? Should I replace the keepers or just reuse the old ones? I'm doing this on the car; what fitting do you all use with air compressors to pressurize the cylinder? How much pressure needed to keep the valve from falling? Is it even necessary to use seals on the exhaust valves? Thanks in advance for answering more of my many questions. Input from members of this site has been an amazing source of information.