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Old 02-15-2016, 05:17 PM   #1
MisterBlah
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Default Head gasket problem from recent engine build

2010 STi. I recently (re)built the short block after blowing it up on the track.

After dealing with an overheating issue and a few of you suggesting it was the head gasket, I have determined it is in fact a head gasket problem. Sort of. More of an "I was an idiot problem".

I've got the engine on a stand right now and right away I realized the head bolts were far looser than they should have been.

I do admit that the head bolts felt "loose", relatively speaking, after doing the engine build initially. And now going back through the FSM, I feel like an idiot for missing a couple of steps(a couple of those "tighten by 90 type steps"). Tightening bolts by an angle and not a torque spec is relatively new to me, so I though I was done when I read step 8 that said to tighten to 70 Nm of torque, especially since it was at the end of the page.

Admittedly, this was my first Japanese engine rebuild and my first that used "stretch" bolts on the cylinder heads. I've built a number of American V8s and they've all been a bit easier, to say the least.

Anyway, I was about the pull the head to replace the head gasket. And I got to thinking: "Do I really need to pull the head and get a new head gasket? or can I just retighten the bolts?" I have not pulled the cylinder heads yet, just loosened the bolts on one side.

It would be awesome to not have to wait a week for new head gaskets.
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Old 02-15-2016, 06:58 PM   #2
MrTris
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Stop. No.

Take the OEM head bolts, and throw them away.

You want the ARP head studs, PN: 260-4701. Buy it for about $185 on Amazon. Wait the two days for Prime shipping.

Thread in studs, tighten with hex/allen key. Follow pattern in 30-60-90ft/lbs - it's too easy to screw up, and you'll get superior results in addition to added reliability and longevity.

Also, you're gonna need a new HG. Don't reuse the one that's been fired already.
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Old 02-15-2016, 07:14 PM   #3
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No, I do not want ARP head studs. And no, I do not care that you think every subaru in existence should have ARP head studs. I also do not need to know how to install head studs. I've done my fair share of high horsepower engines where bigger/better head bolts/studs were necessary. This is NOT one of those cases.
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Old 02-15-2016, 08:20 PM   #4
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Quote:
Originally Posted by MisterBlah View Post
No, I do not want ARP head studs. And no, I do not care that you think every subaru in existence should have ARP head studs. I also do not need to know how to install head studs. I've done my fair share of high horsepower engines where bigger/better head bolts/studs were necessary. This is NOT one of those cases.
So get new TTY fasteners from the dealer along with new headgaskets and be done with it.
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Old 02-15-2016, 08:53 PM   #5
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Originally Posted by Blackfin View Post
So get new TTY fasteners from the dealer along with new headgaskets and be done with it.
I don't need new fasteners.
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Old 02-15-2016, 09:40 PM   #6
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Not for nothing... Wikipedia:



"Torque-to-yield fastener
A torque to yield fastener is mounting hardware which is torqued beyond the state of elasticity and therefore undergoes plastic transformation, causing it to become permanently elongated.[1] Torquing a fastener to yield results in a high preloading of the fastener which, depending on the load frequency and amplitude, can significantly increase the fatigue life of the fastener. When the applied load doesn't surpass the clamping force of the fastener, the strain of the fastener will be lower than when the preloading is smaller than the applied load. It is therefore beneficial in high-frequency high-load situations with a higher risk of fatigue related failure, like a bolted down cylinder head, to use torque to yield bolts.

Compared to normally tightened hardware, a smaller sized TTY bolt/screw may be used while still maintaining the same clamping force. A drawback with TTY hardware is that it normally has to be replaced when loosened, for example when the cylinder head is removed."

What you decide to do with the information is up to you. If you feel you don't "Need new fastners" and want to take the risk, well good luck to you. Let us know how everything turns out.
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Old 02-15-2016, 10:03 PM   #7
z
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Quote:
Originally Posted by MrTris View Post
Stop. No.

Take the OEM head bolts, and throw them away.

You want the ARP head studs, PN: 260-4701. Buy it for about $185 on Amazon. Wait the two days for Prime shipping.

Thread in studs, tighten with hex/allen key. Follow pattern in 30-60-90ft/lbs - it's too easy to screw up, and you'll get superior results in addition to added reliability and longevity.

Also, you're gonna need a new HG. Don't reuse the one that's been fired already.


Quote:
Originally Posted by MisterBlah View Post
No, I do not want ARP head studs. And no, I do not care that you think every subaru in existence should have ARP head studs. I also do not need to know how to install head studs. I've done my fair share of high horsepower engines where bigger/better head bolts/studs were necessary. This is NOT one of those cases.


+1 to this. I did exactly the same when I rebuilt my engine recently.

New stock block. Re-worked heads. ARP head studs.

Those are the cheapest of the ARP but more than reliable. I could tell when I torqued them down that the heads were nice and secure and I wouldn't have to worry.

Why not spend $180 bucks on them for security purposes.

You're "supposed" to replace your stock head bolts anyway when they stretch. I imagine the cost of the 12 bolts from Subaru are probably almost the same anyway.

Or by all means, just re-torque what you have and repost with your results in the future.

Sheet though, if you can't even follow the torque directions for stretch bolts, why wouldn't you want to just replace them with bolts that you can torque (in the proper sequence) to 30 ft/lbs... then 60 ft/lbs and then 90 and be done with it?!

Did you bother to measure the threads in the bolts to see if they were stretched beyond reusability in the first place?

From my reading though, I see that a lot of people just reuse them anyway so if you're up for it, just finish the torque sequence where you left off... (another 90 degrees in sequence, and then another 45 degrees in sequence) and report back periodically to let people know how they hold.

g'luck though!

Last edited by z; 02-15-2016 at 10:17 PM.
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Old 02-15-2016, 10:52 PM   #8
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Quote:
Originally Posted by MisterBlah View Post
I also do not need to know how to install head studs.
No offense but what's the point of this thread then?
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Old 02-15-2016, 11:21 PM   #9
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Quote:
Originally Posted by Rizen View Post
No offense but what's the point of this thread then?
I made a mistake. I recognized that I made a mistake. I admitted that mistake, as I'm sure you read. I didn't come here asking for someone to teach me how to install a set of cylinder heads or to belittle me for something that the FSM doesn't tell me to do, regardless your and everyone else's OPINION.

I wanted to know if a certain set of actions, primarily related to the integrity of the head gasket, was okay. I know that once I remove that cylinder head, I have to replace the gasket. I wanted to avoid that. Clearly no one understood that part. Clearly everyone else was worried about the TTY fasteners that I very clearly did not torque to yield. I mean, was no one reading that I forgot to do steps 9-11, which are the steps to yield the fasteners?

What I've learned based on this thread was that no one knows how to read or the answer to the question I asked. And that everyone wants to sit and be an armchair engineer without actually knowing what will happen. Everyone can say "This will fail" and 100% of the time, that person really doesn't know the full context of that statement and the conditions that need to go along with it.
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Old 02-15-2016, 11:37 PM   #10
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Quote:
Originally Posted by MisterBlah View Post
I made a mistake. I recognized that I made a mistake. I admitted that mistake, as I'm sure you read. I didn't come here asking for someone to teach me how to install a set of cylinder heads or to belittle me for something that the FSM doesn't tell me to do, regardless your and everyone else's OPINION.

I wanted to know if a certain set of actions, primarily related to the integrity of the head gasket, was okay. I know that once I remove that cylinder head, I have to replace the gasket. I wanted to avoid that. Clearly no one understood that part. Clearly everyone else was worried about the TTY fasteners that I very clearly did not torque to yield. I mean, was no one reading that I forgot to do steps 9-11, which are the steps to yield the fasteners?

What I've learned based on this thread was that no one knows how to read or the answer to the question I asked. And that everyone wants to sit and be an armchair engineer without actually knowing what will happen. Everyone can say "This will fail" and 100% of the time, that person really doesn't know the full context of that statement and the conditions that need to go along with it.
I read your post, and I don't know the answer to your question. You just seem to have quite the attitude while responding to people, so I was busting your chops a bit.

You'd probably be better off asking this in the Built Motor forum.
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Old 02-16-2016, 12:23 AM   #11
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Quote:
Originally Posted by MisterBlah View Post
What I've learned based on this thread was that no one knows how to read or the answer to the question I asked. And that everyone wants to sit and be an armchair engineer without actually kno

Dude... first off... clearly you don't know how to read or you would have torqued the f**kin head bolts correctly in the first place.

second... you're asking for peoples opinions, we gave you that. You just don't want to hear it.

Everyone read your post and understand exactly what your situation is. We are all telling you what the BEST COURSE OF ACTION would be for you. If you don't want to take that advice, that's fine. You don't have to be a jackass.

I'm all for you just finishing the torque sequence that you stopped halfway through and report back.

Don't bother replacing the head gaskets... it's always best to git 'er dun as fast as possible.

You don't have to be a dik when you tell people your situation and they give you their opinion of what your next steps should be. Please finish your torque sequence and shut the fu.

Also, please update this post every few thousand miles to prove everyone wrong. (assuming your head gaskets don't leak)
If they do, please feel free to update your findings too.

Last edited by z; 02-16-2016 at 12:28 AM.
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Old 02-16-2016, 08:03 AM   #12
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Quote:
Originally Posted by MisterBlah View Post
I know that once I remove that cylinder head, I have to replace the gasket. I wanted to avoid that.
How much did you loosen the bolts on the one side?
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Old 02-16-2016, 08:04 AM   #13
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To me, it seems the both the headgaskets and the bolts have been compromised already - you ran the engine in your car which resulted in overheating issues.

I would agree with mostly everyone else here to get new bolts and headgaskets just to be sure everything is good at this point; I'd hate to pull the engine out a 2nd time to do what would have been the more time-consuming and mildly more pricey option the first time around, negating the time and money I saved that first time around I decided to just tighten to spec for 10 minutes after spending quite some time pulling and reinstalling the engine.

You seem intent on just torqueing to spec with how it is and just needed some reassurance. I don't think you're going to get that but it would be nice to know how things hold up good or bad.
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Old 02-16-2016, 11:07 AM   #14
helmspeedfab
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New head gasket, if you didn't tty your fasteners the first time around, they will work fine. People can obsess about how they will fail etc etc. They won't. If you had completely tty your fasteners than you would obviously need new ones since they would be beyond the yield rating. But you will need a new head gasket since the fire ring was likely damaged from not being sealed properly.
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Old 02-16-2016, 11:35 AM   #15
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Why would someone that tracks a car not want to do it right, or anyone for that matter? To save a few dollars?

No room for a half-assy approach if you plan on beating a car. It WILL cost you more money down the road if you do. Spend $ now, or $$$$ later. You have been warned.
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Old 02-16-2016, 12:47 PM   #16
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For the record, I don't know a single Subaru tech that doesn't reuse head bolts. You simply skip the beginning where you stretch them by backing them off.

Just a note, there is a limit to how many times these bolts can be reused as they are torque to yield and if you go beyond that spec, you'll be doing the job again. Because my car had 185k on it and because of how cataclismic my head gasket failed, I opted to replace the bolts with ARP studs.

Last edited by zore; 02-16-2016 at 01:11 PM.
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