When did the hardened valve seats go into production in the slant 6's? I assume around 1970/71 as no lead was becoming available then. But I am not 100% sure.
I'm asking so to know when to worry about ugrading the seats in a rebuild versus not. Tnx!
It was later than 1970/71. I think it was 1975 when catalytic converters were first widely used on automobiles. Those demanded the use of unleaded fuel.
