Here is what available for the valve mod after I did my built. But it will increase the cost trememdously so I stay with standard size valve. I don’t know how much gain with the 5 angle job but it’s included in the build. I’m not going all out crazy, but just enough to hanging with some local fast cars
Machine spring seat to accept single or dual valve springs
Ferrea® 1.0 or 1.5mm oversize stainless steel valves
Install new valve seats
Ferrea® dual titanium springs
Ferrea® titanium retainers, locators, and keepers
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If it’s included, you can’t beat that. Ferrea is good stuff, I have (can’t remember the specific model of valve) their SS valves in my head and they are great quality.