Originally it has a rpm limiter on 6500 rpm. When we drove those engines when they weren’t rare we also removed the rpm limiter. And drover it occasionally to 8000 rpm with stock internals. Never had a valve float, but it is tricky business. Knowing bmw they always keep some headroom but it is playing Russian roulette with your engine. And now cherries those engine especially if you have a reall 2L. They are becoming rare, especially the I version.
In the US the 2L motors are relatively easy to come by since from 77 to 79 every E21 we got here had one. Also the 2002 was very popular. You can still buy one for not too much money but they are definitely starting to become a little bit more scarce. The 2L is great especially since it has a stock forged crankshaft.
You should be able to get near 8000 rpm - I didn't hear that deep rattle you normally get a full valve float, when the engine is right up at its mechanical limit. Maybe just jam it down for a few seconds???
