I have a 87 ford f-250 with a 6.9. It has a banks sidewinder turbo and i was wondering what would be a safe amount of boost without replacing head bolts with head studs. right now its boosting around 7-8psi.

 

10 is about the most you should go. Buut... the banks is non wastedgated. So you only get what you get. You can eek a little more out of it with injectors and bumping the pump up a smidge. A good exaust goes a long ways too.

 

My turbo is the wastegated sidewinder.

 

10 should leave you a little safety margin.

I ran 15 on stock head bolts, but when I pulled the heads you could see where the fire rings were seeping on all the cylinders.
I have no doubt failure was not far in the future running that much boost.