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Old 06-13-2016, 04:04 PM
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simplyconnected simplyconnected is offline
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I think so, Tom. Advancing the spark usually adds much more HP because the fuel burns sooner, to the point where knock and ping become excessive. Ethyl Corp., back in the day, developed high octane fuel that slowed the burn which in effect also retarded the timing. Later, we called this 'premium' fuel. Originally, we pulled up to the pump and told the attendant, "Fill 'er up, Ethyl."

So now, instead of advancing the spark for a sooner burn, most folks retard timing so it burns later. HP goes down and efficiency goes down but because the fuel is only partially burned it actually helps cool the combustion chamber.

Modern cars RAISE their coolant temp and advance spark so the fuel can burn more completely. They don't have heat issues because the heads are aluminum, pistons are hypereutectic alloy and the rings are moly. All of which quench heat far better than the materials of the day. - Dave
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