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Stephen is correct in that none of the Opel CIH engines imported into North America had hardened valve seat inserts, as in distinct separate inserts that are pressed into place. But beginning in 1971, Opel advertised their engines as being suitable for using no-lead gas. Of course, it wasn't a complete truism, since valve recession still occurred. In 1973 (I believe), Opel started using a process to "flame harden" the valve seat (or was it actually induction harden? Whatever, similar processes). But from what I have read, that process, along with different head metallurgy, created a valve seat that is prone to cracking. This might be repairable with pressed-in seat inserts, if the crack is not to deep or long. Otherwise the head is a total loss.

Do you need to install hardened inserts to run unleaded gas? There has been lots of discussion on this point. My opinion, for what it is worth, is that an engine that is run lightly (and put to bed dry) will operate satisfactorily on unleaded gas without either lead substitute or inserts. But if you plan on a high mileage, high output engine, plan on installing hardened inserts at the first valve job. But don't do a valve job just because you want to use unleaded gas without lead substitute. Wait until you actually need a valve job.

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