I have Ferrea 5000 in me RA IIs.
I have RA IV valvues inthe 48s, and would prefer 1-piece valves like Ferrea.
Long Stems for 1.7" or 1.8" is quite good.
Knurled guides went the way of SBC rebuild shops.
Thin-leaf guide are nfg.
Pressed-in Iron guides are okay i suppose, but dunno.
Pressed-in bronze guides seem good.
Spiral rifle groove is a feature of most guides i have seen.
Be sure to get positive-seals that match your guide boss dia. .550", .530"
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