JM7 is suitable for titanium, there are even better alloys available. I would stay away from CuBe due being very poisonous unless strictly necessary for purpose (nitromethane etc.),
I'll ask around, had a little chat regarding the subject last Saturday with a machinist specialised in high performance cylinder head repairs.
- Pekka -
Well... Not just b/c of fuel/temperature.
It also helps with valve bouncing when using a high valve spring pressure.
I'd stick to CuBe, specially with Ti valves.
There are alternative nickel-aluminum-bronze and nickel-silicone-chrome-copper alloys which will do their task very well with titanium
but granted, CuBe is very hard to beat as an exhaust seat material due to it's heat dissipation and corrorision durability properties
in extreme applications. My advice is to ask around what is commonly used and available locally.
-Pekka-