Have I got hardened valve seats?

It is often difficult to determine whether valve seat inserts have been fitted before, when viewed only from the chamber, – the original machining usually left a pattern which is not to dissimilar to how it looks with seat inserts.

The usual give-away as to whether inserts have been fitted is to feel round the short radius with your finger. If an insert has been fitted to an unmodified head there is invariably a bit of a ledge in the short radius where the seat finishes. (short radius – the tight side of the 90 deg bend between valve seat and port. Alternatively described as where the bottom [when the head is on the engine] of the port turns the corner to the valve seat.)

Inserts, if fitted, may be hardened but could also be of the cast iron variety used in the past to effect repairs or reclaim worn seats. The simplest way to confirm is to use a small file on the inside of the insert (NOT where it forms the valve seat) to see whether it marks/cuts into it easily or not.