That would, imo, depend on the application.
Some would say any, I have run with them though in a stockish street only application.
Some sort of 1000 hp race car, zero would be my answer.
If it's a 130 tooth flywheel a new one is under $75 at Rockauto LUK LFW215
the 143 tooth one is alot more, PIONEER FW161
And will also mention that some claim the heat spots that "disappear" after turning are actually still there and can cause issues with a new clutch and PP.
If they are that visible after turning, myself i would scrap it.
