Will a 1973 318 engine have the hardened valves and seats for the use of unleaded fuel? Thank for any info here.
John

No .I believe they started using hardened seats after 1975 when all gas went unleaded.

Late 72 was the first year of hardened valve seats, but it was only on the Slant six. Like stated before, I don't think it was until 75 that the V8s got them.

I've heard though that the hardened valve seat wear is a pretty long term effect and that running a slightly cool thermostat and lower octane (if CR permits) will even help reduce wear. I've even been told that unless the engine is built for very high HP or to be used as a daily driver that the hardened seats aren't really worth doing unless you are sending the heads into a machine shop for other work.

IMO you should never run older heads without hardened valve seats with unleaded gas. What happens is when the valve opens and closes it rotates slightly. When the valve closes, tiny spot welds connect between the valve and seat. When the valve opens since the valve is stronger than cast iron seat it tears a little of your seat off. Over a short time and use your seats will recede, which is what happened apparently to a 1966 440 I recently machined. The exhaust valve on the 440 was almost a quarter of an inch recessed into the head.

i read on Allpar.com as well as few mechanical engineering books I have for school that Chrysler used hardened valve seats in the Mid 30s. Before the introduction of lead, and when Alcohol was being used as an anti-knock agent....too bad they didn't stick with it huh.