Pontiac Firebird SD-455 Engine - New-Age Super Duty
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Many Pontiac shops use stones to grind the necessary angles into the valve seats. The angles used for these heads are 30, 45, 60, 75, and 82 degrees for the intake and 30, 45, 55, and 82 degrees for the exhaust. RaceKrafters uses a special machine that cuts with a high-quality tool instead of grinding. This is the proper and modern procedure for the best performance. It creates much more accurate valve-seat angles than a stone. The procedure improves low-lift flow on both ports when the valve is just coming up off the seat. View Related Article
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