How can I tell if I have hardened valve seats? Cast number is 2843169. Casting number matrix says that it can be both, hardened and not.

https://www.slantsix.org/articles/parts-matrix/jpg.htm

I think all drool tubes were not.
Peanut heads are.

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Hyper_pak

I thought they started using hardened seats around 1972ish in preparation for unleaded gas.
At least that is so with the V8 engines.

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-MattMan
LEANED & MEAN

1973 was the first year for factory induction-hardened exhaust valve seats on the Slant-6 engine. 1974 was the last year for the spark plug tubes. 2843169 could have the factory induction hardening or not, depending on when it was made. But the induction hardening only goes down about the depth of a spark plug gap (0.030" to 0.040") and at this late date, you're best off just having hard seats installed. It doesn't add much cost to a valve job or head recondition, and it's smart insurance.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.