[KiWinUS]

I agree wholeheartedly with Ronnie & Pete. There’s thousands of old engines of all brands running great all over the world with cast heads & blocks and no hardened seats. I myself have built many since unleaded gas came along with Zero issues so far. Besides flatheads many of those orange engines even hot rod engines and no seat inserts. There’s many other issues that can cause seat or valve failure. As Pete eluded to lean mixture is a big one along with having correct valve lash.