Unleaded Gas

[Mulletwagon]

Thanks for all the responses. Much good info but never really did get the answer to the question regarding rebuild of engines up to the late 70s. If rebuilding say a 1965 289 that was all original, should the heads be rebuilt with hardened valve seats and stainless valves ? Does current gas have additives that make such mods unecessary ? As it was explained back in the 70s, the lack of lead allowed "microscopic" spot welds between the valves and the seats which caused the valve/seat erosion. Would agree the lack of lead in current gas does not effect Model A mills, and maybe no flatheads for that matter.

[Dodge]

A 1965 289 could go either way. If its a stock 195hp motor and driven easy you can
get away with stock valve seats.
The problem comes when you start running the motor hard and using higher than stock
valve spring pressures and wild cam timing.
You see the problem in Muscle Cars and in Trucks that are pulling loads all the time.
If your worried in your Model A then put in hard seats or use Marvel Mystery Oil.