it seems like they use VG30DETT (300zx TT) valves and RB26 (Skyline GTR) retainers and valve springs.
I hadn't heard of this before. Can anyone shed some light on this, from previous experience or translating the website a little better?
I can!
When I was having the head built for my car (still under construction...) I contacted Supertech because I heard they were who FM got their valvetrain parts from.
At the time, FM was only having them manufacture +1mm intake valves, but I wanted to do both intake and exhaust. So Willy at Supertech figured out that the 300ZX valves had the correct head and stem diameters and stem length.
The only problem was the keeper grooves were the wrong shape for the Miata keepers and the Nissan keepers wouldn't sit right in the the Supertech retainers.
So what we had to do was customize the grooves in the Nissan valves (which is not an easy task once the valves are already heat-treated). But we got it done.
As is the story of my life on this project car, after paying a premium for custom parts, before I got around to having my head assembled, FM had commissioned Supertech to manufacture the Miata-specific +1mm exhaust valves that they now sell.
Such is the high cost of surfing the bleeding edge...
:-({|=
Bill