1985cucv

i was wondering at what hp or psi of boost are head studs needed? is it really related to hp or just boost numbers thanks

jhenson

If I had to say, it's probably more of a boost pressure issue. Depends on who you talk to as to what kinds of numbers you'll get. Some will say 40 lbs and other will say they are running over 50lbs and no problems. Personally for the sake of your pocketbook, I would say anything above 40 psi is hitting the dangerzone. I wastegated my 62/65 to 35 lbs and up to that point it's still pulling like a raped ape on the top end!

madhat

I'd say 40.

If you are planning to continue to build, I'd drop the money in putting 14mm in.

bansh-eman

One thing I have always wondered was... Ok so now you got the mother of all mother studs... What happens when they pull the threads out of your block? I may just be a little too skeptical, but wouldn't the block threads now be the weak link rather than the studs?

annabelle

Studs will "stretch" out of specs.

1985cucv

well i was thinking about some 90's and a different turbo but no where over 550 horse and then i could just set the wg to 40 or 45.

goatbrain5.9

for the extra insurance i would run them, it's not like it's a ford and you have to remove the cab to do the studs. I would much rather spend the money on studs and enjoy my turbo and power than hope the stock bolts are not going to stretch and have to limit what my turbo can put out. It's kinda like reverse engineering

1985cucv

ok so when are springs needed then?

goatbrain5.9

good question i'm not sure i'm running 90's and a set of twins and i'm going to be running 110# springs

bansh-eman

That's kind of what I am getting at. If you have a stronger stud, it doesn't stretch. Something will eventually give. Now that the studs won't stretch, wouldnt that make the threads in the block the newest weak link?

Justice4all

Some guys have pulled the threads, but the percentage is small and it usually points to improper installation. I have a set of 625's torqued to 155 ft/lbs and have run it that way for more than two years pushing up to 75 PSI of boost. In fact I just checked the torque on the studs a couple days ago and nothing has changed since the initial installation and retorque sequence.

That being said, I hardly believe 625's are needed for just a single turbo upgrade. The standard A1's or ARPs are fine to run with any of the S300 singles.

dieseloutlaw1

I am planning on installing twins on my truck with in the next month, I know i need studs, what about head gasket?? I've got 111,000 miles, replace with new then stud or what??

1985cucv

ok so if i need them which ones should i get i dont need the real expensive ones what are the part numbers? thanks

madhat

If you are just planning to stay under 650 or so, the 625's will do fine. I don't have the specific part number.

As far as HG's go, from what I understand, the stocker is a good one. I have heard something about a marine gasket, however, I do not know much about it.

XLR8R

The necessity of head studs is a function of combustion pressure, which normally varies directly with boost pressure.

14mm studs aren't the best solution - machining the larger threads removes material & rigidity from the block and $$ from your BOMB budget.
ARP 2000s are fine for most builds, if you need zero failure go with the nickel-base 625+.

Studs (any threaded fastener) will stretch by design, and yield if their tensile strength is insufficient for the load applied.
Stretch is good, yield (permanent deformation) is bad... think of studs as very heavy-duty springs that barely move.
All studs stretch - the 625+ will stretch more (contain more combustion pressure) before they fail (yield)... length change (stretch) is measurable though minute - think of stretch as absorbed load.

Studs are naturally far less likely to pull threads - without tensile stress within the block's thread engagement length, load is shared equally among all engaged threads.
Bolts stretch when torqued to desired clamp load, so most of the shear stress in the block occurs in the 1st engaged thread, followed by 30% less on the next thread, etc. until the bottom end of the bolt is usually just along for the ride (until the upper threads strip out and the load is accordingly carried by the next lower threads).

Also, prevailing torque is much higher on a bolt fastener than a stud fastener (even with correct torque lube), due to the difference in number of rotating threads - so more accurate (and ultimately higher) clamp loads can be developed with studs.

If your MLS head gasket is sealing well, leave it in place and stud it (ARP 2000, A1, H11, 625+, etc.) to your desired power production goal; if the head is coming off anyhow, consider a 12V gasket & O-rings for the ultimate in cylinder head sealing.