[ford428]

almost all Fords are dificient in exhaust valve size(except MR,HR 427)..not knowing what head u are going to run the suggestion here would be to run the largest exhaust valve that space will permit...If u are running a C80E-N head w/2.09-166 stock valves..take a MR exhaust valve 1.72 and ttry to fit that in . also use 70 degree reamer (after noting seat with dykum blue) to open throats up to the bottom of seat. also exhaust guides run much hotter than intakes, machining these too close will guarantee valve stem seizing with resulting bent pushrods.