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PSA: Subaru changed headbolts (improved) from 2010 onwards.


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Just a heads up for those who are unaware, Subaru actually seems to be using better head bolts after 2010.

 

See this document:

http://www.sbintl.com/tech_library/tech_bulletins/TT00012_revised_cylinder_head_bolts_in_2010_Subaru_2.5L_engines.pdf

 

As I have recently replaced the head gaskets in my 2010 GT, I noticed the head bolts were black instead of the usual gray color. Here is what the new DOHC bolt looks like :

11095AA160.jpg

 

The document above mentions a higher torque figure than the service manual.

 

For comparison, the FSM states the following when putting the heads on:

Tighten the cylinder head bolts.

(1) Apply a thin coat of engine oil to washer and

bolt thread.

(2) Tighten all bolts to 29 N·m (3.0 kgf-m, 21.4

ft-lb) in alphabetical order.

(3) Tighten all bolts further to 69 N·m (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 49 N·m (5.0 kgf-m, 36.1

ft-lb) in alphabetical order.

(6) Tighten all bolts by 80 to 90° in alphabetical

order.

(7) Tighten all bolts further by 40 to 45° in al-

phabetical order.

CAUTION:

The tightening angle of the bolt should not ex-

ceed 45°.

(8) Tighten bolts (A) and (B) further by 40 —

45°.

CAUTION:

Make sure the total “re-tightening angle” of the

step (7) and (8) does not exceed 90°.

 

 

Where the revised steps are found to be:

Clean the bolt threads and the bolt holes in the cylinder block. To avoid erroneous tightening of the

bolts, clean 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 29.5 ft/lbs (40 Nm) in alphabetical order as shown in Figure 2.

4. Tighten all bolts to 70.1 ft/lbs (95 Nm) in alphabetical order. If the bolt makes a stick-slip noise

(squeaking sound) during tightening, start over from Step 1. In this case, the cylinder head gasket can

be reused.

5. Loosen all bolts 180° in the reverse order of installing and loosen them an additional 180°.

6. Tighten all bolts to 7.4 ft/lbs (10 Nm) in alphabetical order.

7. Tighten all bolts to 22.1 ft/lbs (30 Nm) in alphabetical order.

8. Tighten all bolts to 51.6 ft/lbs (70 Nm) in alphabetical order.

9. Tighten all bolts 80-90° in alphabetical order.

10. Tighten all bolts an additional 40-45° in alphabetical order. Do not exceed 45°.

11. Tighten bolts (A) and (B) further by 40-45°. Do not exceed 45°. Caution: Make sure that the total

tightening angle of steps 10 and 11 does not exceed a total of 90°.

 

If you notice the part in bold, we are talking an increase of 21Nm.

 

The document provided also has revised steps for SOHC. However I have not compared the difference between that and the FSM.

The document above does have a part numbers for both old vs new bolts for DOHC and SOHC.

 

If I were doing head gaskets on a 2009 or older 2.5L engine, personally I would use the new bolts if I couldn't justify ARP studs. Roughly $40 for 12 bolts via partsouq.

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