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Old 02-18-2008, 06:00 AM   #1
bugeyes
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Default ARP head studs V's OEM sti head bolts

Has anyone ever seen any conclusive tests done to determine the clamping force of these head fixings given all other factors are equal.

Sure you can re-use the ARP studs but I dont care about that.

Which setup hold the head down better and has less potential stretch once installed.
Are the ARP studs any better?
As the Subaru head bolts/studs are quite long they are probably more prone to stretch than shorter bolts?.

Is there any real factual data?????
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Old 02-18-2008, 11:22 AM   #2
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im not sure about facts, i just know that everyone uses them and i use them, im sure there are some factual data about this, im sure someone will chime in
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Old 02-18-2008, 03:43 PM   #3
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subscribed...
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Old 02-20-2008, 05:27 AM   #4
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Read up on the differences between bolts and studs then come back. There is a substantial difference
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Old 02-20-2008, 10:23 AM   #5
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Quote:
Originally Posted by bugeyes View Post
...

Is there any real factual data?????
i'm curious too...

I have never really heard of anyone blowing a headgasket or whatnot due purly to insane amounts of combustion chamber preasure and the head not being held down tight enough...

anyone ??
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Old 02-20-2008, 01:30 PM   #6
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Quote:
Originally Posted by blowbyu24 View Post
im not sure about facts, i just know that everyone uses them and i use them, im sure there are some factual data about this, im sure someone will chime in
I'm not so sure about that... but we will see.

Quote:
Originally Posted by Optical NZ View Post
Read up on the differences between bolts and studs then come back. There is a substantial difference
While there may be a substantial difference, it does not answer the original question. Given the ARP setup may be X times stronger, does that make a difference? That is the question.

Quote:
Originally Posted by IllNastyImpreza View Post
i'm curious too...
I have never really heard of anyone blowing a headgasket or whatnot due purly to insane amounts of combustion chamber preasure and the head not being held down tight enough...
anyone ??
I would be curious to see what other builders say. In 99% of the high HP engine build I have done the ARP head studs were used. It is difficult to conclude from that any clear indication of a problem with the stock head studs.

However, I would add that head gasket failures (ignoring overheated engines) are not the most common failure in the EJ world. On most of the built engines something else seems to be the weak link. Most builders will likly stick with the ARP studs as a results of them proving to be very reliable, even with out direct evidence of the stocks being unreliable.

If you are building a motor, and the ARPs are widely used without problem, which way would you go? Given the cost of rebuild, most end up using the ARPs.

Jeff
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Old 02-20-2008, 06:35 PM   #7
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also the ability to reuse them over and over is another benefit.

Josh
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Old 02-20-2008, 06:47 PM   #8
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I have heard that the OEM headbolts ARE stretchbolts. As in, they are designed to stretch when the proper torquing procedure is applied. (Ie, tighten them, and then loosen them, then tighten to certain torque and then two sets of 90 degree tightening.) If you only torque them to, say 80 lbs, then you most likely will have a failed HD with the OEM bolts. I haven't read about any HG failures when the subaru procedures were used to torque the bolts. I have done it twice using the OEM bolts and have not had a failure yet.(EDIT - I had one side fail, but cannot determine with leak-down test - Going to upgrade to ARP since I am wanting a torque monster - Was only running 18 lbs boost max)

Some people will reuse the OEM bolts, but I strongly urge you to replace them, as they have been "stretched" already.

Last edited by paintbing; 03-13-2009 at 06:44 PM. Reason: OEM Headbolts may have failed me
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Old 02-20-2008, 11:05 PM   #9
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OEM bolts are stretch bolts, as stated in the post above me.

I know from experience that enough boost WILL lift the head and blow your head gasket. Went back to the garage, installed arp head studs, and magically no problems since.
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Old 02-20-2008, 11:13 PM   #10
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S L O W W R X installed ARP headstuds on his car and blew the head gasket due to boost pressure. Although he also forgot to retorque them after the initial break-in period. But these are the things we learn by mistake.
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Old 02-20-2008, 11:25 PM   #11
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Quote:
Originally Posted by paintbing View Post
I have heard that the OEM headbolts ARE stretchbolts. As in, they are designed to stretch when the proper torquing procedure is applied. (Ie, tighten them, and then loosen them, then tighten to certain torque and then two sets of 90 degree tightening.) If you only torque them to, say 80 lbs, then you most likely will have a failed HD with the OEM bolts. I haven't read about any HG failures when the subaru procedures were used to torque the bolts. I have done it twice using the OEM bolts and have not had a failure yet.

Some people will reuse the OEM bolts, but I strongly urge you to replace them, as they have been "stretched" already.
fyi I work at a subaru dealer and in the past 4 years I have done probably at least 50 headgasket replacements and have never once replaced the bolts. you only need to follow the manufacturers procedures for new bolts to do the initial stretch. When reusing them I just torque them to 74 ft/lbs starting with the center bolts and going outwards in a circular pattern. To this day not one has returned with any issues.
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Old 02-20-2008, 11:32 PM   #12
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Quote:
Originally Posted by novacivic View Post
fyi I work at a subaru dealer and in the past 4 years I have done probably at least 50 headgasket replacements and have never once replaced the bolts. you only need to follow the manufacturers procedures for new bolts to do the initial stretch. When reusing them I just torque them to 74 ft/lbs starting with the center bolts and going outwards in a circular pattern. To this day not one has returned with any issues.
That's good to know. Do you put the bolts in the same holes they came out of? The reason I ask is because the center bolts are torqued to 25lbs and then advanced 180 degrees; whereas the outer 4 are torqued to 13lbs and then advanced 180 degrees. This would seem that the center two bolts would be stretched just a tad more. I would think that swapping positions may pose a problem.

Anyway, when I rebuild my motor, I like using new parts for the peace-of-mind. Go ahead and re-use the bolts, but "will" they hold? a high boost build may be too much for the re-used headbolts. Anyway, just my $0.02. Happy modding!
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Old 02-20-2008, 11:47 PM   #13
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Quote:
Originally Posted by paintbing View Post
That's good to know. Do you put the bolts in the same holes they came out of? The reason I ask is because the center bolts are torqued to 25lbs and then advanced 180 degrees; whereas the outer 4 are torqued to 13lbs and then advanced 180 degrees. This would seem that the center two bolts would be stretched just a tad more. I would think that swapping positions may pose a problem.

Anyway, when I rebuild my motor, I like using new parts for the peace-of-mind. Go ahead and re-use the bolts, but "will" they hold? a high boost build may be too much for the re-used headbolts. Anyway, just my $0.02. Happy modding!
on dohc engines it doesn't matter where you put the bolts as all four are identical but on the sohc the center ones have bigger diameter washers then the outer ones and if you put the bigger ones on the outside and try to tighten them you will crack the head. and also I have put together quite a few built motors for customers and reused the bolts everytime with no issues. plus with torquing them to 74 ft/lbs it will be more precise than angle torquing them
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Old 02-20-2008, 11:52 PM   #14
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im using ARP studs for my sti swap, hope its good like most of you have said
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Old 02-21-2008, 12:57 AM   #15
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Quote:
Originally Posted by STiBottom View Post
S L O W W R X installed ARP headstuds on his car and blew the head gasket due to boost pressure. Although he also forgot to retorque them after the initial break-in period. But these are the things we learn by mistake.
So are you saying after say 1000 miles after i break in my build i should retorque my ARP's?
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Old 02-21-2008, 05:34 AM   #16
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If it was fact that the ARP head studs need to be re-torqued after 1000 miles I think I could safety state that 99% would never use them.
It's just such a major pain in the a$$ to get to the things.
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Old 02-21-2008, 09:02 AM   #17
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Quote:
Originally Posted by novacivic View Post
fyi I work at a subaru dealer and in the past 4 years I have done probably at least 50 headgasket replacements and have never once replaced the bolts. you only need to follow the manufacturers procedures for new bolts to do the initial stretch. When reusing them I just torque them to 74 ft/lbs starting with the center bolts and going outwards in a circular pattern. To this day not one has returned with any issues.
Same here. However I follow the FSM to the letter on normal customer builds. For the WRX/STi or modified Forester/Outback/Baja engines, I have one small addition to the FSM instructions.

Quote:
Originally Posted by paintbing View Post
That's good to know. Do you put the bolts in the same holes they came out of? The reason I ask is because the center bolts are torqued to 25lbs and then advanced 180 degrees; whereas the outer 4 are torqued to 13lbs and then advanced 180 degrees. This would seem that the center two bolts would be stretched just a tad more. I would think that swapping positions may pose a problem.
For the SOHC heads, yes, the center two bolts are different then the outers and have a slightly different TQ procedure. DOHC is all the same and I've put the bolts all sorts of ways and never had a come back.

Quote:
Originally Posted by bugeyes View Post
If it was fact that the ARP head studs need to be re-torqued after 1000 miles I think I could safety state that 99% would never use them.
It's just such a major pain in the a$$ to get to the things.
The factory procedure has a re-TQ in it. The ARP instructions do not have this. If you use the ARP instructions you will ALWAYS have HG failure within 20,000~30,000 miles, if not sooner.

It has been proven that using the FSM procedure with ARP studs and STOCK headgaskets....extremely LOW rate of failure, however, I've still seen them come back.
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Old 02-21-2008, 12:29 PM   #18
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wait a minute....

My builder installed my block on my heads with a cometic HG & ARP studs... I'm at about 600 miles on the engine so far...

Do I need to re-torque it at 1,000 miles ???

why wouldn't they tell me something like this...
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Old 02-21-2008, 01:50 PM   #19
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Quote:
Originally Posted by IllNastyImpreza View Post
wait a minute....

My builder installed my block on my heads with a cometic HG & ARP studs... I'm at about 600 miles on the engine so far...

Do I need to re-torque it at 1,000 miles ???

why wouldn't they tell me something like this...
In theory, if they used the SUBARU method of TQ'ing the heads down...it should be fine until the cometic gasket fails.

Otherwise, if they used the ARP instructions, you need to re-TQ it NOW NOW NOW and not a second later.
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Old 02-21-2008, 03:58 PM   #20
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How can you possibly use the subaru method to torque down the head bolts on ARP head studs.
The priciple is totally different.

The torque procedure for the oem bolts is designed around the amount of stretch of the bolt, the amount of stretch is dependent on the type of material (logical enough).
The material of the ARP stud is different so logically the same procedure cannot be applied.

This all stems back to the original question.

There seems to be lots of opinions however NOBODY can quote any factual clamping force details.......
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Old 02-21-2008, 04:47 PM   #21
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Quote:
Originally Posted by WJM View Post
In theory, if they used the SUBARU method of TQ'ing the heads down...it should be fine until the cometic gasket fails.

Otherwise, if they used the ARP instructions, you need to re-TQ it NOW NOW NOW and not a second later.
well.... iether way It couldn't hurt to re-torque them .... right ??
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Old 02-21-2008, 05:36 PM   #22
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It never hurts to check any fastener.
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Old 02-21-2008, 05:38 PM   #23
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Quote:
Originally Posted by bugeyes View Post
How can you possibly use the subaru method to torque down the head bolts on ARP head studs.
The priciple is totally different.

The torque procedure for the oem bolts is designed around the amount of stretch of the bolt, the amount of stretch is dependent on the type of material (logical enough).
The material of the ARP stud is different so logically the same procedure cannot be applied.

This all stems back to the original question.

There seems to be lots of opinions however NOBODY can quote any factual clamping force details.......
Ya know, I may not know the EXACT SCIENCE behind it, and YES the PRINCIPLES are different from bolts to studs w/nuts....but TWO things remains constant:

1. Using the ARP supplied instructions ALWAYS result in failure, stock or cometic gasket.

2. Using the SUBARU FSM method ALWAYS results in longer headgasket life compared to the ARP supplied instructions.

I'm not going to argue principles and physics and stretch bolts...but I will argue MY EXPERIENCE to the end. Especially since I have MULTIPLE experiences of the same thing.

I would also like to see factual clamping force data.

Quote:
Originally Posted by IllNastyImpreza View Post
well.... iether way It couldn't hurt to re-torque them .... right ??
Yup.
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Old 02-21-2008, 05:56 PM   #24
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ok looks like I'm gona bring my car by DSG this spring for a checkup before I do any driving... (she's got a mysterious clicking noise as well.... )
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Old 02-21-2008, 10:18 PM   #25
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Here is the deal that all ya'll experts aren't mentioning about ARP studs.....


ALL ARP STUDS MUST BE CYCLED 3 TIMES BEFORE THE FINAL TORQUE ON EACH STUD!!!!!

What does that mean you ask....???


It means when you are building your engine, use the subaru fsm torque pattern, and snug all the studs down at the first torque interval.....

1st, you must make sure that you have the studs threaded far enough into the cylinder block so that you don't tighten down to the shank or un-threaded portion of the stud.... DO NOT USE A THREAD TAP TO CLEAN OUT THE CYLINDER BLOCK!!! ONLY USE A THREAD CHASER TO DO SO... Also, this should have been done way before the install of the headgaskets and heads... but you can blow out the holes ok with pressurized air.....


Now, start on the first stud to be torqued, (A), and torque and loosten it 3 times to the full torque spec recommended by ARP.....

You will feel the stud stretch the first one or two times, and on the 3rd time, it will torque up very solid....

I usually go ahead and torque it the final time after the 3rd cycle....

ALWAYS USE ARP MOLY LUBE FOR PROPER TORQUE.... Put lube on the threads, on both sides of the washer.....

Using ARP moly Lube, your torqued fastener will be much more accurate and properly tightened than if you use 30wt motor oil.....



how do I know all this??

I worked for a shop that deals ARP for 9 years and I have built countless engines myself....


There is no need to re-torque ARP studs that have been properly cylced the way I described..... it is done and done on the 4th time.....


PERIOD.

GOOD LUCK
RYNO


P.S.- I use studs in every engine I build, overkill on some, necessary on others.....
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