Head Gasket Torque

[steve56]

Doing head gaskets on 08 Impreza..There are  two different sets of installation instructions. The instructions I'm used to are middle two head  bolts to 25 ft/lbs, outer four head bolts to 15 ft/lbs ,along with a couple of additional  angle torques..

The other set of instructions are all six head bolts to 31 ft/lbs, along with a couple of  slightly different angle torques. 

 

Which installation instruction set should be used for 08 Impreza ?  Also I've seen YouTube videos where the 21 ft/lbs then 51 ft/lbs torque and then two 180 degree loosening steps are omitted. The rational is these steps are for head bolts stretching, and if you are reusing the head bolts ,they are already stretched. Which method is correct, re stretch the head bolts or not re stretch the head bolts ?

[GeneralDisorder]

It's not for stretching - it's to pre-lube the female threads. 

 

22, 51, back off, 29, 90 degrees, 45 degrees, and then 45 degrees on center bolts only.

 

Before head installation, clean block threads with brake clean, heavily lube a bolt and run it into each hole till you hit bottom. Repeat for every hole, lubing the bolt for each. Then install the head and bolts with heavy assembly lube like Amsoil engine assembly lube. 

 

GD

[golucky66]

1) Clean the bolt threads and 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 ect.

2) Apply a thin coat of engine oil to washer and bolt thread.

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

4) Tighten all bolts to 95 Nm (9.7 kgf-m, 70.1 ft-lb) in alphabetical order.

CAUTION: If Bolt makes stick-slip sound during tightening, repeat the procedure from step (1). In this case the 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) Tighten all bolts to 30 Nm (3.1 kgf-m, 22.1 ft-lb) in alphabetical order.

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

9) Tighten all bolts by 80 to 90°in alphabetical order.

10) Tighten all bolts by 40 to 45°in alphabetical order.

CAUTION: The tightening angle of the bolt should not exceed 45°. 
 

11) Further tighten the bolts (a) and ( by 40 - 45°.

CAUTION: Make sure the total "re-tightening angle" of the step (10) and (11) does not exceed 90°.

 

 

Right out of the service procedure on AllData. Which I've used at least a dozen times.

Edited October 22, 2017 by golucky66

[golucky66]

Cleaning the block's head bolt holes is by far the most important step in my experience. 

I typically spray out each hole with brake clean well, then blow it with compressed air - time each hole (just to safe) and never had one creak on me using 5w30 conventional oil 

[Gloyale]

1) Clean the bolt threads and 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 ect.

2) Apply a thin coat of engine oil to washer and bolt thread.

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

4) Tighten all bolts to 95 Nm (9.7 kgf-m, 70.1 ft-lb) in alphabetical order.

CAUTION: If Bolt makes stick-slip sound during tightening, repeat the procedure from step (1). In this case the 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) Tighten all bolts to 30 Nm (3.1 kgf-m, 22.1 ft-lb) in alphabetical order.

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

9) Tighten all bolts by 80 to 90°in alphabetical order.

10) Tighten all bolts by 40 to 45°in alphabetical order.

CAUTION: The tightening angle of the bolt should not exceed 45°. 

 

11) Further tighten the bolts (a) and ( by 40 - 45°.

CAUTION: Make sure the total "re-tightening angle" of the step (10) and (11) does not exceed 90°.

 

 

Right out of the service procedure on AllData. Which I've used at least a dozen times.

 

Yeah.  the double 180 degree loosening is a widely repeated mistake. After the first 180 they are floppy loose zero torque.  Never seen it in a Factory FSM  Typo following EJ engines around the Webs.

 

Use subaru FSM data, not Alldata......trust me they are frequently misinformed unfortunately.

[steve56]

It's not for stretching - it's to pre-lube the female threads. 

 

22, 51, back off, 29, 90 degrees, 45 degrees, and then 45 degrees on center bolts only.

 

Before head installation, clean block threads with brake clean, heavily lube a bolt and run it into each hole till you hit bottom. Repeat for every hole, lubing the bolt for each. Then install the head and bolts with heavy assembly lube like Amsoil engine assembly lube. 

 

GD  

Thanks for clearing things up,.and the double 180 degree loosening misinformation too. Do those torque specs also apply to the late 1990s and early 2000s ej22/25 ?  Can head bolts be cleaned with a wire wheel on bench grinder ?

[GeneralDisorder]

Yes that applies to all EJ engines. 

 

DO NOT wire wheel the bolts. They are aluminized and this is an anti-friction coating. If washing them in mineral spirits doesn't get them clean (rusty, pitted, etc) then they need to be replaced. They are inexpensive from the dealer. You only need to replace damaged, rusted, pitted bolts. Reuse the good ones. 

 

GD