Well, you really should replace the valves, springs, etc, because the factory valves are friction welded 2 piece valves, and are known to separate, it's not a really common occourance, but it can happen, and it's not pretty. When I built my Cleveland for street duty, I used Ferrea 5000 one piece stainless valves so I wouldn't risk it.

Just my $.02

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'73 Montego MX 357C Homebuilt EFI, 9.5:1 comp, mild cam, 30lb injectors, A9L computer, Moates.net chip, 70mm TB, 76mm C&L mass air.