Boost pressure and drive pressure are the reason for studs, but drive pressure is the most important. It that gets too out of whack, bye-bye headgasket. Depending on the setup, around 50 psi of boost or higher depending on drive pressure.

Timing comes into play as well. I watched a 2nd gen 24v on a dyno spit coolant from the front of the head gasket but was only pushing 35psig. Turns out he had stacked tuners. I think timing had a lot to do with it.

Actually boost and so called HP have little to do with HG failures.

Too much timing which equates to LOTS of Cylinder pressures (and temps) is what jacks up head gaskets..

I was making close to 800 hp and running 11.50's on Stock Head bolts.. Although my head was o-ring'd though.. I got the 625's for future mods..

After a melt down, I had to get a different head and didn't have it o-ring'd. Now I just use the MLS HG with my 625's at 150 ft. Lbs. It's holding 70-75psi and 850+ hp just fine..

But if you were to need a bit better clamp force on a budget, just simply pull Each stock head bolt ONE AT A TIME.. lube them with some ARP thread lube... Take them back to right at 100 ft. lbs.

After ALL have been pulled, lubed, and torqued to 100, then start in the middle and work your way out.. Take them all up in 5 LB. INCRIMENTS!!

105, 110, 115, 120, 125, 130, 135.....

Let the threads cool for about 10 mins between each pull of 5 lbs..

It is possible to take stock bolts to 150 ft. Lbs. because thats were mine were at the 800 hp level with o-rings..

But I would recommend about 125-135 for that little extra you guys will need for a small 62 or 64 turbo... Approx 45-55 psi..

This will help save some money in the long run...if you don't plan to go to big on fuel and air...

After a couple of heat cycles, you may want to do one retorque.. Just to make sure they all still pull to the max 125-135 (whatever you ended with ).

Hope this helps... But if you have the money, I really suggest just buying studs and be done with it.. 625's if you really never wanna have to worry again.... Remember, do it Right the FIRST time!!


Reminder - Too much timing is the enemy!! Not boost.


David

Saw this after my post... You are correct Sir!!

Great info above David. Thanks for your input!! [guitar]

Oops, yeap I forgot timing and the affect it has on cylinder pressure. So shoot me...LOL

My dealership gave me a lifetime warranty if I get serviced with them, will them popping the hood and seeing headstuds put the nix on that deal?

It could, but they'd have to prove you put more fuel to it.. Depending on whatever failure you took it in for...

It will certainly raise an eye brow.

If I return my bullydog to stock will it leave a footprint?

Yes.

ARP 2000's are tool steel, should be oiled prior to installation and are subject to hydrogen embrittlement - besides developing lower effective clamp load, they simply don't last as long as ARP's super alloy.

625+ studs are nickel-base (much of their cost reflects the alloy surcharge), able to generate 14mm-range clamp loads and can be successfully used through multiple seasons & engine builds.

Thread lube type + torque wrench setting = static clamp load.
This is critical, since there's no practical way to measure stretch in a headstud application.
ARP's legacy lube is much better than what they started pushing last year - less scatter & more of a known factor... fastener thread friction typically soaks up >85% of applied torque in dry installations.
Of course, break-torques are superior to line-torques for thread polishing purposes.

Combustion pressure is the only factor that can stretch fasteners enough to lift a head & compromise gasket sealing integrity; low-RPM peak torque is particularly egregious in this regard.