Running unrebuilt original heads? Might need lead substitute above 8500gvw

[AuroraGirl]

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this is a 1986 TSB from GM. so over 8500gvw (so C6P 3/4 tons, all 1 tons,) after 1979 need substitute , while anything above 5000 gvw 73-78 need lead substitute.
not sure how many unrestored trucks engines are out there, but figured to post it after I found it

 

[fast 99]

Convertors were on lighter duty trucks. Probably the same head but lead would kill cats. In the past I have seen several early heads with extreme valve recession. Almost makes economic sense to buy aftermarket aluminum heads rather than spend money making original heads compatible with unleaded fuel.

Lead has been a hot topic in aviation where it is still used but substitute fuels are coming on the market. REAL lead additive is still available from one manufacturer. How long who knows.