Re: Hardened valve seats or lead additive...

Posted by Ross On 2012/11/27 22:24:52

These flatheads run very low valve spring pressures and don't turn too fast so it is not an issue. I have several hundred thousand miles on various flatheads from Kaiser to Stude to Packard with unleaded fuel, no additives, and no problems.

While your engine is apart, be sure to check the fit of the exhaust valves in the guides as this is a common wear area and heat transfer out through the stem is important to keep the valves happy.