Which head studs???
 

Everything I have is in my sig. I won't be doing anything else to it. I'm getting air in my coolant and from everything I've read it's the hg or I'm lifting the head. Could it be anything else? If not will I be okay with 425's or do I need 625's? Any thoughts greatly appreciated

In my opinion I'd go 625s I know theyre expesive but they never corrode and they of course are better quality. Like anything you usually get what you pay for. anyhow just my .02:c:

Yep I agree on the 6.7's its best to go with the 625's

jpthomso
 

I am getting ready to start making mods to my 6.7. Should I go ahead and replace the studs? If so, how tough of a job is this? Can they be changed one at a time, or does the whole head need to come off and a new gasket with the new studs put back?

I'd say go ahead and do it jobs not hard as long as the gaskets not blown you can pull one bolt drop in a stud and then torque it to 90 ft/lbs then move to the next one (we followed torque sequence) then just go in the torque sequence from there just my .02

I have never had any issues with the 425's if installed properly.

How extreme are you gonna go with mods? Injectors, aftermarket turbo? If you are doing any of those then the 625's are what you want

how much are the 625 studs?

around a grand from what i have seen

What kind of turbo could I run to get rid of the drive pressure problem? Don't wanna go too big...won't be doing injectors.