How to determine a safe red-line?

flyfish said
....so I would take it to 6k and see what she does. Have fun with it. :D

That's where I'd be going to. I have a stock bottom end, 80,000 mile engine in my car with a 268H cam, headers, intake and a 650 4V carb.

I spin it to 5500 and a tad more sometimes when blasting through the gears, no issues here....................yet! :D