RPM with a 4.0 sohc??

[charlie brown]

how many rpms is safe with a 4.0 sohc motor?

i have a juanco tunned/flashed computer and gets right up 6+ and it seems like it will go more. i am not used to that many r's so what is safe. the motor is all stock but the computer.

 

[Dirmaid]

I wouldn't really trust the engine turning that many rpms. The peak Horsepower is right around 5300, so anything beyond that is losing power and causing unneeded wear and tear. What kind of tuner are you using?
Also, my personal rule of thumb is that if the company that made it only put a tach that went to 6k, don't push your luck with revving higher.