Date: Mon, 31 Jan 2000 18:09:00 -0500 From: [email protected] (Dave Williams) Subject: hardened valve seats? To: [email protected] -> My question is about hardened valve seats, I have put them -> in the past rebuilds I have done, but since then I heard -> some people say that they weren't nessecary. I learned theyInserted seats are for repair. They interfere with heat flow from the valve; the ports have to be ground to blend the seat in; improper installation (can you tell with your naked eye?) will let them come loose, with potential for catastrophe. The cutting necessary to install the seats weakens the head and can promote cracking, particularly if the head is subjected to higher than stock pressures or heat, ie a high performance engine.
You want inserted seats about as badly as you want a veneral disease.
Most shops call them "hardened" seats; most inserts are plain old cast iron, like they just carved out of your heads. True hard seats are Stellite and they cost over $10 each, and they're righteous bastards to cut a seat on.