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Old 08-25-2008, 08:56 PM
BogiesAnnex1 BogiesAnnex1 is offline
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Originally Posted by mightycarlo10
I think i screwed up. Basically i built a 383 from a '76 Monte Carlo 350 engine. I'm pretty sure they dont have hardened seats and i've been runnin regular 93 octane. Does anyone know if these do or do not have hardened seats and what kind of damage i could have done? I really dont care if the heads are trashed because they are pos 882 heads. I only care if it could have damaged the rings or bearings or something.
These have hard seats. Actually contrary to hod rodders belief, soft seats without leaded fuel don't wear out any faster than they did with lead. The failure mode is different but the miles it takes to get there is about the same.

With leaded fuel, the exhaust valve became encrusted with deposits that interfered with heat transfer, depending on how hard you drove, in the good old days, exhaust valves and often intakes burned thru the seat or worse anywhere from 30 to 50,000 miles. Shops did a land office business in ring and valve replacement jobs. With soft seats and unleaded fuel, the failure mode is the pounding of the seats into the head. Once seal is lost the hot gases might also burn the valve but usually engine power goes away before this happens. Plus this is much more restricted to the exhaust, opposed the where both sides usually burnt with leaded fuels. The pound in process, also, takes about 30 to 50,000 miles, it isn't anything that happens over night.

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