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rotorwrench · 07-26-2020, 09:47 AM

They started discontinuing hardened seats in 1950 or 51. Truck engines kept them on the exhaust seats only. Rotator valves coming in during the 1951 model year and modern fuels diminished the need for the hardened seats. These engines should at least have hardened seats on the exhaust valves to run unleaded fuel.

Lead additive would be unnecessary for an engine with lower compression. Most flatheads are limited on how high the compression ratio can be taken. The compression chamber has to include room for those valves to work and there is no way to get around that.

07-26-2020, 09:47 AM	#4
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,425	Re: Is lead still needed? They started discontinuing hardened seats in 1950 or 51. Truck engines kept them on the exhaust seats only. Rotator valves coming in during the 1951 model year and modern fuels diminished the need for the hardened seats. These engines should at least have hardened seats on the exhaust valves to run unleaded fuel. Lead additive would be unnecessary for an engine with lower compression. Most flatheads are limited on how high the compression ratio can be taken. The compression chamber has to include room for those valves to work and there is no way to get around that.