Those margins will run just fine. I admit to having ground the diameter of a valve down to get a thicker margin, but only if the seat is low enough on the face to still be nicely placed. You're making me confess to things some guys would shudder at.
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"It don't take but country smarts to solve the problem" (Smokey Yunick)
'41 Merc Town Sedan / 260" 8CM engine
'66 Fairlane four door / "warmed up"
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