Hardened valve seats in 390 engines

[64ZCODE]

Hi all. Wondering if anyone knows when Ford started putting hardened valve seats in the 390 engines? I have a '64 Tbird with a stock 390 and have been adding lead substitute with every fill up. I wouldn't mind stopping doing that if in fact my engine has the hardened valve seats. Feedback?

[cacockrum]

If your ’64’s engine has not been rebuilt it will have the old composition valve seats and seals. I don’t know when the change to the hardened variety occurred, if all Ford engines started using them at the same time, or if there was a multi-year phase-in, but the change coincided with the elimination of lead in the gasoline. According to our friends at Google, the production of unleaded gasoline for automotive use began in 1970, and after 1974 the rate of change-over increased such that the production of leaded gas was almost completely eliminated by 1990. (Actually, unleaded (or “white”) gas was available for as long as I can remember for use in Coleman stoves, blow torches, etc, albeit in limited quantities.) At the time there was some controversy as to whether a lead additive was needed. Perhaps by now there has been enough experience to answer that question?

[64ZCODE]

I've been googling around on the topic of hardened valve seats and unleaded gasoline, and I have to say - it's a clear as mud. Apparently hardened valve seats were introduced beginning in 1974. One point of view is that if an engine is seeing sustained heavy duty (like pulling heavy trailers) and running on unleaded gas, then you may see valve seat recession if the valve seats are not hardened. But for normal use including our classic cars, unhardened seats will not be a problem.

Then again, I may just be spreading tribal knowledge...

[RAVEN]

Actually I was told the same thing by my long term engine rebuilder. When I was having my heads redone for my RAVEN build I asked about the hardened valves and seats. He told me under severe load situations the hardened parts were needed but under cruising, soft petal applications the original factory set-ups would last a long time. My fellow has done fork truck motor builds with his father for going on 50 years, and in my mind knowledgeable. He has the CDN contract for CAT diesel engine head Re and Re, so that also gives me confidence.
Hope I am not being trivial either 64Z. Have another one on me,

W