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Old 10-19-2017, 02:06 PM   #1
bd3
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Default ej25 head bolt torque pattern/head gasket

SO from what I have been gathering from around here on this beautiful forum is that, you CAN reuse your head bolts. So now I plan on reusing them (wasnt overheated once, never been apart before) Question is do I skip the first few steps on the torque sequence because my head bolts are already stretched? Or should I continue to go down the list from the get go.

Here is the torque pattern I had found and believe to be true for majority of SOHC
(stole this from poweredbysnail)

https://forums.nasioc.com/forums/sho....php?t=1062633

"This is strait from the Subaru Manual"

1. Apply a coat of engine oil to washers and bolt threads.
2. Tighten all bolts to 22ft-lb in alphabetical sequence, and then tighten all bolts to 51ft-lb in alphabetical sequence.
3. Back off all bolts by 180 degrees first; back them off by 180 degrees again.
4. Tighten the bolts (A) and (B) to 25ft-lb.
5. Tighten the bolts (C), (D), (E) and (F) to 11ft-lb
6. Tighten all bolts by 80 degrees to 90 degrees in alphabetical sequence.
7. Further tighten all bolts by 80 degrees to 90 degrees in alphabetical sequence.
Caution: Ensure the total "re-tightening angle" [in the two previous steps] do not exceed 180 degrees.


Now do I skip directly to step 4 or start at the top, from what I gather after step 3 the bolts are pretty loose some people say they are backed off completely.
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Old 10-19-2017, 07:17 PM   #2
Charlie-III
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Sigh.....

We are assuming this car is from your sig

Yes, use the bolts, yes, start from step one regardless.

Have a nice day.
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Old 10-20-2017, 12:38 PM   #3
bd3
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Thanks Charlie and yes it is, so far youre the only one who likes to help although you don't seem to happy to but I do appreciate it.
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Old 10-20-2017, 01:08 PM   #4
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Quote:
Originally Posted by bd3 View Post
Thanks Charlie and yes it is, so far youre the only one who likes to help although you don't seem to happy to but I do appreciate it.
ha ha ha, agreed start at 1

your bolts are not 'already stretched' by the way.
They stretch under load, which is how a bolt exerts pressure. Then they retract back to original length when released.
If they stretched BEYOND their plastic deformation level then you would absolutely not want to re-use them ever.

the first few steps are to pull the head down evenly first just so it isn't crooked or something
wouldn't be necessary in an ideal world
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Old 10-20-2017, 01:48 PM   #5
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I've also heard that the first sequence is to compress the gasket evenly before the final torque but I don't know how sound that theory is.
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Old 10-20-2017, 03:03 PM   #6
Charlie-III
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Quote:
Originally Posted by bd3 View Post
Thanks Charlie and yes it is, so far youre the only one who likes to help although you don't seem to happy to but I do appreciate it.
No, not "unhappy" to provide info, in your case, a bit out of the ordinary, so I replied in a measured noncombative answer.
The basic question has has been asked before, but yes, yours is a bit different.
No slam at you.
Hope,it helped.

Quote:
Originally Posted by rtv900 View Post
ha ha ha, agreed start at 1

your bolts are not 'already stretched' by the way.
They stretch under load, which is how a bolt exerts pressure. Then they retract back to original length when released.
If they stretched BEYOND their plastic deformation level then you would absolutely not want to re-use them ever.

the first few steps are to pull the head down evenly first just so it isn't crooked or something
wouldn't be necessary in an ideal world
.maybe a typo......
Elastic deformation means the fastener goes back to original dimension, as much as it can.
Plastic deformation means you "went too far"......,
No, I'm not an engineer, just decades doing various work that makes me read up on engineering stuff.
If I'm wrong, show me, I can adjust.
Hoping you had an autocorrect that changed your reply.

Quote:
Originally Posted by monkeyposeur View Post
I've also heard that the first sequence is to compress the gasket evenly before the final torque but I don't know how sound that theory is.
AFAIK, you are correct, the first sequence is to compress the basket to block/head surfaces. Then, get the clamping force.

I have a "nuts and bolts" thread that covers some of this on this forum.
Read, maybe it makes sense.

Last edited by Charlie-III; 10-21-2017 at 05:49 AM.
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Old 10-20-2017, 04:28 PM   #7
bd3
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Yes it helped Charlie and again I appreciate your replies.
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Old 10-20-2017, 04:45 PM   #8
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Quote:
Originally Posted by Charlie-III View Post

Dude, wrong, just wrong....maybe a typo......
Elastic deformation means the fastener goes back to original dimension, as much as it can.
Plastic deformation means you "went too far"......,
No, I'm not an engineer, just decades doing various work that makes me read up on engineering stuff.
If I'm wrong, show me, I can adjust.
Hoping you had an autocorrect that changed your reply.
.
no your right, I used the wrong term. Elastic would be correct.
I just wanted to point out they were not stretched other than while under load.
Since they now have 'torque to yield' bolts people start confusing the two and think once it's used it is permanently stretched, so I figured he might have thought that applied.
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Old 10-20-2017, 05:12 PM   #9
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Yes, you can reuse head bolts - I have been told by Subaru as many as 4 or 5 times. There is suppose to be a specification for checking length but I've never seen it.

Your head torque values are for an earlier engine - NOT a 2009 N/A EJ25 Impreza. You should have:

Use a new cylinder head gasket.

(1) Clean the bolt threads and the bolt holes in the cylinder block.
CAUTION:
To avoid erroneous tightening of the bolts, clean out the bolt holes sufficiently by blowing with compressed air to eliminate engine coolant etc.


(2) Apply a sufficient coat of engine oil to the washer and bolt thread.

(3) Tighten all bolts to 40 Nm (4.1 kgf-m, 29.5 ft-lb) in alphabetical order.

(4) Retighten all bolts to 95 Nm (9.7 kgf-m, 70.1 ft-lb) in alphabetical order.
CAUTION:
If the bolt makes stick-slip sound during tightening, repeat the procedure from step (1). In this case, the cylinder head gasket can be reused.


(5) Loosen all the bolts by 180 in the reverse order of installing, and loosen them further by 180.

(6) Tighten all bolts to 10 Nm (1.0 kgf-m, 7.4 ft-lb) in alphabetical order.

(7) Retighten all bolts to 30 Nm (3.1 kgf-m, 22.1 ft-lb) in alphabetical order.

(8) Retighten all bolts to 60 Nm (6.1 kgf-m, 44.3 ft-lb) in alphabetical order.

(9) Retighten all bolts by 80 90 in alphabetical order.

(10) Retighten all bolts by 40 45 in alphabetical order.
CAUTION:
The tightening angle of the bolt should not exceed 45.


(11) Retighten bolts (a) and (b) by 40 45.
CAUTION:
Make sure the total tightening angle of steps (10) and (11) does not exceed 90.


Bolts (a) and (b) are the two center ones the outside four should be an "X" pattern. do (a), (b) and then "X" in each step except step 11.



The first tighten/loosen is to seat the head and gasket as there supposedly a tendency for the head to slip around. These head are located with dowels so your guess is as good as mine.
When I started working at Subaru I was taught to skip 3, 4, and 5. Several hundred SOHC, DOHC, and turbo EJ head gaskets later and have never had a problem. I have even heard field engineers drop hints that it was acceptable.
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Old 10-20-2017, 06:05 PM   #10
Charlie-III
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Quote:
Originally Posted by Elbert Bass View Post
Yes, you can reuse head bolts - I have been told by Subaru as many as 4 or 5 times. There is suppose to be a specification for checking length but I've never seen it.

Your head torque values are for an earlier engine - NOT a 2009 N/A EJ25 Impreza. You should have:

Use a new cylinder head gasket.

(1) Clean the bolt threads and the bolt holes in the cylinder block.
CAUTION:
To avoid erroneous tightening of the bolts, clean out the bolt holes sufficiently by blowing with compressed air to eliminate engine coolant etc.


(2) Apply a sufficient coat of engine oil to the washer and bolt thread.

(3) Tighten all bolts to 40 Nm (4.1 kgf-m, 29.5 ft-lb) in alphabetical order.

(4) Retighten all bolts to 95 Nm (9.7 kgf-m, 70.1 ft-lb) in alphabetical order.
CAUTION:
If the bolt makes stick-slip sound during tightening, repeat the procedure from step (1). In this case, the cylinder head gasket can be reused.


(5) Loosen all the bolts by 180 in the reverse order of installing, and loosen them further by 180.

(6) Tighten all bolts to 10 Nm (1.0 kgf-m, 7.4 ft-lb) in alphabetical order.

(7) Retighten all bolts to 30 Nm (3.1 kgf-m, 22.1 ft-lb) in alphabetical order.

(8) Retighten all bolts to 60 Nm (6.1 kgf-m, 44.3 ft-lb) in alphabetical order.

(9) Retighten all bolts by 80 — 90 in alphabetical order.

(10) Retighten all bolts by 40 — 45 in alphabetical order.
CAUTION:
The tightening angle of the bolt should not exceed 45.


(11) Retighten bolts (a) and (b) by 40 — 45.
CAUTION:
Make sure the total “tightening angle” of steps (10) and (11) does not exceed 90.


Bolts (a) and (b) are the two center ones the outside four should be an "X" pattern. do (a), (b) and then "X" in each step except step 11.



The first tighten/loosen is to seat the head and gasket as there supposedly a tendency for the head to slip around. These head are located with dowels so your guess is as good as mine.
When I started working at Subaru I was taught to skip 3, 4, and 5. Several hundred SOHC, DOHC, and turbo EJ head gaskets later and have never had a problem. I have even heard field engineers drop hints that it was acceptable.
EB, thank you for your insiteful info, I trust what you post. You have likely done more than even the most adventurous of peeps on this forum.
You and I may nitpick, but on this, we are in agreement......FWIW.......


BTW, have a nice ride.....

Last edited by Charlie-III; 10-21-2017 at 05:36 AM.
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Old 10-20-2017, 06:34 PM   #11
Elbert Bass
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Specification change year to year, model to model. Heck, the FB/FA engines are mere youngsters (4 years) and there are at least 4 different head torque specs and procedures depending on which model/year.

Great ride BTW, a quick 12 miles on hallowed ground only rivaled by Gettysburg. Fog was lifting and deer were everywhere - including the roads and trails.
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Old 10-23-2017, 05:51 PM   #12
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Thank you Elbert Bass.
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Old 11-08-2017, 09:03 AM   #13
bd3
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(1) Apply a thin coat of engine oil to washer and bolt thread.
(2) Tighten all bolts to 29 Nm (3.0 kgf-m, 21.4 ft-lb) in alphabetical order.
(3) Retighten all bolts to 69 Nm (7.0 kgf-m, 50.9 ft-lb) in alphabetical order.
(4) Loosen all the bolts by 180 in the reverse order of installing, and loosen them further by 180.
(5) Tighten all bolts to 42 Nm (4.3 kgf-m, 31.0 ft-lb) in alphabetical order.
(6) Tighten all bolts by 80 to 90 in alphabetical order.
(7) Tighten all bolts by 40 to 45 in alphabetical order.
CAUTION: The tightening angle of the bolt should not ex- ceed 45. ( c ) ( b ) ( f ) ( d )
(8) Further tighten the bolts (a) and (b) by 40 — 45.
CAUTION: Make sure the total "re-tightening angle" of the step (7) and (8) does not exceed 90


Ok now I am loosing my mind I decided to search for a manual for a 2009 impreza and found one online and this is the torque sequence given. Can anyone confirm which one to go with?

Very similar but also different.
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Old 11-08-2017, 09:17 AM   #14
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Quote:
Originally Posted by bd3 View Post
Ok now I am loosing my mind I decided to search for a manual for a 2009 impreza and found one online and this is the torque sequence given. Can anyone confirm which one to go with?

Very similar but also different.
Remember what Elbert Bass said:
Quote:
Originally Posted by Elbert Bass
Specification change year to year, model to model. Heck, the FB/FA engines are mere youngsters (4 years) and there are at least 4 different head torque specs and procedures depending on which model/year.
Without definitive proof that the manual you found actually applies to your exact model/production date, I'd go with EB. He's a lot more "tuned in" with what Subaru's latest specs are than most.
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Old 11-08-2017, 09:38 AM   #15
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Ok thanks Samurai Jack I was leaning towards EB's spec only because of the more steps and less torque on each step.
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Old 11-12-2018, 07:30 PM   #16
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I am assuming that the process using the torque values with the higher torque for the centerbolts (A and B, black heads etc), as I am working on a a dubious age Ej25 block in a 2006 Impreza currently where all bolts are the same visually. Which would apply to the process in post #1......?
Can anyone confirm please?
Thanks

Edited:
After I pulled engine discovered that engine had been replaced before thus it’s not the original from factory.

Last edited by cmyachtie; 11-12-2018 at 09:16 PM.
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Old 11-13-2018, 09:28 AM   #17
Charlie-III
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Quote:
Originally Posted by cmyachtie View Post
I am assuming that the process using the torque values with the higher torque for the centerbolts (A and B, black heads etc), as I am working on a a dubious age Ej25 block in a 2006 Impreza currently where all bolts are the same visually. Which would apply to the process in post #1......?
Can anyone confirm please?
Thanks

Edited:
After I pulled engine discovered that engine had been replaced before thus its not the original from factory.
Black heads?
I am not aware of any special marking on head bolts, swap them around, it's fine. It is only the location on the head tha varies the values.
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Old 11-16-2018, 10:58 PM   #18
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Ok, thanks I was watching a YouTube vid of a tear down and those Head bolts were red and black on the heads and that made me ask the above question
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