Thread: Headstud comparison

Won't reach it with this one as the car is for sale, however this is not part of the topic at hand.

On post #43 I said that some of it may be human error, but I'm not blaming it ALL on the user. Where online did they admit to having a problem with the SR20 APR head studs? Aren't they all made of the same material regards of the car it goes on? I know that the diameter of all of them will not be the same, as the ones for the IS were pretty big. Did they mention the threads as being the defect?

They are not all the same material, these have some similar tensile strengths with different characteristics and many o fthem are used for different apps such as rod bolts, head studs and exh studs;

8740 chrome-moly- 180k-210kpsi
ARP2000®- 220k psi
L19 steel- 260k psi
AERMET® 100- 280k psi
INCONEL 718- 220k psi
ARP3.5® (AMS5844)- 260k psi
CUSTOM AGE 625 PLUS® 260k psi
TITANIUM 180k psi

The thread depth is the problem, the studs are not long enough. Only engaging a few threads puts undue stress on those few threads in the block rather then dispersing the force through a larger suface area, I am sure you get what I am saying.

ARP does not have it listed online, call em about the old sr20 studs and see what they say? These new ones are supposed to be better, but appear to be the same design from visual inspection according to a few on this site.

I would like to see a set of the gtir ARP studs part number 202-4303 vs sr20 head studs p/n 102-4701 also the ARP gtir studs vs OEM gtir bolts.

^Interesting info........I will give them a call and ask them how many different materials they use for different blocks and why? (what materials would conflict from block to block in comparison).......I would assume that a company would use the strongest material available for the goal and be done with it....Design error is part of life sometimes......Only time can tell if a new product will hold up without years of testing if there is not enough information for it.

I am a drafter and I deal with strength and material equations often, so I know there are problems that can occur........It there is some hidden money factor in here for them using a weaker material that caused the flaw, then they need to speak up (which I don't think would happen).......This would be sh*ty for a company to do this with a conscious thought of knowing that would happen. I will dig into this some more and ask them if the thread flaw was the only problem with the old vs the new.

popped headgaskets twice on my vet. the car was sitting at around 470whp at 24lbs. the first time i thought it was the cometic hg. but couldnt find anything that showed where it blew out. never did i think about what was really happening. the second time i used a stock 20V steel hg. it held but then it happened again. pulled the head and it appeared that nothing blew the gasket into a water passage. just there was water everywhere. after seeing matt's greddy bolts in person, i then realized on why the arp's are ****, and that under hard boost the head was actually lifting, that since the arp's only lockon to the first two threads in the block,... that when a great amount of psi is in the combustion chamber... those two threads give a little.... a little enough for the headgasket not to seal.

Locks on to two threads? Lol bro something was really messed up here. Period.

ill say it again. the arps are a ****ty disign. there is no in between..there is no right in saying ill use them since im staying under a level of horsepower. they were not engineered properly.

How do you figure this? Any charts for compression under stress test on why they are sh*tty?

at this point ill take my chance with 1/2 inch head studs, or the old school...factory head bolts.

Factory over ARP...explain please?

here is another expierence i have had to back up that they are designed wrong. when you install arp's they tell you to install them, but not at all to tighten them. this means that when you go to take them out (one of a few reasons)... they should just screw out. nope they dont. not at all. you damn near have to vice-grip them to get them out. why? becuase they are now locked onto the top few threads in the block, from tightening the nuts when the head was installed.

The reason that you only do them hand tight is because the studs stretch a certain amount based on ARP torques spec. With a shank stud its solid, has not stretch no force. The only force you have is that of the torque you apply. When them stretching that is why they have you torque PAST your factory specs. With the pressure applied it applies a "clamp" type style. Which is by far superior than that of a standard stud.

Also, remember that they ALWAYS suggest to retorque after the engine had been ran and warmed up. This is a MUST with all of ARP's head studs.




this picture shows the problem if you can see it. there is no problem with the strenght of the arp stud. the ploblem is where it holds into the block. as you can see for one... the factory head stud threaded portion is much longer. the shank of the factory bolt is also undercut. the arp threaded section is a lot shorter. the shank of the stud is alco larger than the threaded section. this means that the stud will stop screwing down in the block becuase it has run out of threads causing the larger shank of the stud to put stress on the deck. so now when you go put that monster torque on the nut, it will pull only on the deck where the shank of the stud has interfered with.

the last time i checked...IS300 do not have sr20's in them. the sr20's that are making lets say 1000whp. dont have arp head studs holding the head together.

im done.

I just briefly spoke with a very friendly engineer at ARP, and directed him to this thread, as well as sending him the picture that was obtained (the ARP vs. OEM thread catch picture).

He will be contacting me shortly, to provide me with additional information.

From what I gather at this time, the difference between the old and new studs isn't physical. From what he explained to me, the torque #'s that you need to apply are increased with the new set, and I'd assume that this would be due to a higher grade material. I don't know this to be true yet, so I will not say until I have any additional information from ARP.

More to follow. (I also asked as to why so few threads are actually in the block, vs. even OEM studs.)

that's good news I guess

^It really is and I hope he/they read the WHOLE thread........

So in the vets its only holding onto two threads as well?

I have build as much sr20s as lance.but after lifting the head about 5 times with the arps on my test mule, i went back to stockbolts. after 25lbs of boost and about 550whp they are still going strong and this is with a cometic gaskit with coper spray.

p.s mkiv when it comes to sr20s in GA am the king ask any sr person who has the fastes sentra in atlanta and see who they say.