Lead substitute

After a 40 ish year career testing engines on dynos and in vehicle and having a slew of older cars, typically, our "toys" don't see enough annual miles to really worry about valve recession. And, if you are planning an EFI system if it uses an oxygen sensor to run "closed loop" fueling, any lead in the fuel will kill the sensor fairly quickly. The e10/15 fuels are harder on the old fuel system in general. I run e0 recreational fuel in my 300J. It's 91 octane and doesn't evaporate in the carbs like e10 does.

My 2 cents worth.
George
 
Tetraethyl lead formed a deposit on the exhaust valve and seat that helped cushion the shock of the valve seating, thus, preventing valve seat recession. When it was outlawed, valve seat recession became a BIG problem and lead substitutes helped but weren't a real cure for the loss of lead in gasoline.

Pull the heads off and get hardened exhaust valve seats installed and be done with it. My 440 had that done decades ago and I never had any issues. In fact, every pre'72 engine I have has hardened exhaust seats installed and I never had one fall out which is an ugly rumor floating around.
'69 Road Runner 383
'68 GTX
'53 Chrysler with '54 heads
265 cube inline six in my '48 Chrysler
 
In '98 I hauled my family and our hardtop trailer to the west coast,...over 7,000 miles in my 68 Newport 383. When I go back I was seriously down on 2 cylinders.

I tossed on a set of post '74 heads and continued enjoying the car. They worked great. Loss of compression, sure, but not enough to worry about

In my current 40's, 50's and 60's vehicles I use a few ounces of Marvel Mystery Oil (not an advertisement, a statement of fact) with each fill up as well as the occasional dose of seafoam. My '49 Packard and my Plymouth flatheads both work well with it, and have shown no signs of deterioration (other than regular maintenance) over the long miles that I tend to torture them with.

Keep smiling.
 
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