Originally Posted by Drothgeb (Post 580479)

Jeez, you guys are really going at it over those bolts.:scare2:

FYI....

The stock head bolts are less than 11mm and have an ultimate tensile strength of 150,000 psi

A 12mm grade 12.9 bolt is 12mm and has an ultimate tensile strength of 175,000 psi and are at least 38% stronger than the stock head bolts.

The standard ARP stud is 12mm and has an ultimate tensile strength of 190,000 psi and is at least 55% stronger than the stock head bolts.

Heat will affect all of these bolts over time, even the studs will weaken over time.


If you use a torque wrench to do the 90lbs + 90 degrees to the 12.9 bolts, you will find that it equals +/- 135lbs of torque instead of the 120 or so you get with the stock bolts. That is an indication of higher bolt strength and higher clamping force.:tu:

Now it's not quite as simple as I've seemed to indicate here, but the simple facts are... The stock head bolts are very good, the 12.9 bolts are better, and studs are even better than that. If you're at 550hp or less, you can save a few bucks and probably get by with the bolts. More power than that, twins or O-rings you might want to go ahead and use studs.

Originally Posted by 2500HeavyDuty (Post 580232)

My buddy stephen had a 12v that he ran a fatbastard turbo on it and pegged his 50psi gauge all the times, he had stock head bolts, no big deal :dmi: had it for a long time with that setup and had no problems.

Originally Posted by Smokem (Post 580645)

Was his Phat Bastard 87mm or 95mm? I'm going to guess here that you confused what he really had with something that just had a catchy name. I would imagaine he also had the Super Duper Dragon Atomizers and Dragon Fire Flame Throwers to round it all out?

Originally Posted by 2500HeavyDuty (Post 580760)

i forget exactly what it was theres way too many name variations and stages for cummins parts its just getting stupid, im sure you would agree.