Subaru EJ25 Head Gasket torque sequence - which to use?

[vanis13]

Why all the different head gasket sequences? ( And more importantly, which one to use?)

Check out these different ones for a 2004 EJ25 SOHC non-turbo

I labeled them 2004 A, 2004 B, 2004 C (screen shots attached below)

Look at 2004 B – It has a total of only 90 deg after backing off 306deg. How can that at all be tight enough? Seems like a step is missing.

I’m working on a project that is not vehicle specific. Seems like all EJ25 SOHC heads non-turbo should be the same.

Thoughts?



****2004-A

2) Tighten the cylinder head bolts.

(1) Apply a coat of engine oil to washers and bolt threads.

(2) Tighten all bolts to 29 N·m (3.0 kgf-m, 22 ftlb) in alphabetical sequence.

Then tighten all bolts to 69 N·m (7.0 kgf-m, 51 ftlb) in alphabetical sequence.

(3)

Back off all bolts by 180° in reverse order of installation, and back them off again by 180°.

(4) Tighten all bolts to 42 N·m (3.9 kgf-m, 31 ftlb) in alphabetical sequence.

(5)

Tighten all bolts by 80° — 90° in alphabetical sequence.

(6)

Tighten all bolts by 40° — 45° in alphabetical sequence.

NOTE:

Do not tighten the bolts more than 45°.

(7) Further tighten bolts (a) and (b) by 40° — 45°.

NOTE:

Ensure the total “re-tightening angle” in the [former two steps], do not exceed 90°.



****2004-B

2) Tighten the cylinder head bolts.

(1) Apply a coat of engine oil to the washers and bolt threads.

(2) Tighten all bolts to 29 N·m (3.0 kgf-m, 22 ftlb) in alphabetical sequence.

(3)

Tighten all bolts to 69 N·m (7.0 kgf-m, 51 ftlb) in alphabetical sequence.

(4)

Back off all bolts in reverse order of assembly

By 180°first; back them off by 180°again.

(5)

Tighten again all bolts 40° — 45° in alphabetical sequence.

CAUTION:

Do not tighten bolts more than 45°.

(6) Tighten again the bolts (a) and (b) to 40° — 45°.

CAUTION:

Do not tighten bolts more than 90° in total angle.



****2004-C

2) Tighten the cylinder head bolts.

(1) Apply a coat of engine oil to the washers and bolt threads.

(2) Tighten all bolts to 29 N·m (3.0 kgf-m, 22 ftlb) In alphabetical sequence.

Then tighten all bolts to 69 N·m (7.0 kgf-m, 51 ftlb) In alphabetical sequence.

(3)

Back off all bolts in reverse order of assembly

By 180° first; back them off by 180°again.

(4)

Tighten the bolts (a) and (b) to 34 N·m (3.5 kgf-m, 25 ft-lb).

(5) Tighten bolts (c), (d), (e) and (f) to 15 N·m (1.5 kgf-m, 11 ft-lb).

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

CAUTION:

Do not tighten bolts more than 90°.

(7) Further tighten all bolts by 80 to 90° in alphabetical Sequence shown in figure below.

CAUTION:

Ensure that the total “re-tightening angle” [in the former two steps], do not exceed 180°.
_________________
83.5 Westy with Subaru 2.5, 4 spd manual, center seat, COLD A/C on 134a!, Winter camp heated with an Espar B4 gasoline furnace

www.SuperVanagon.com - some stuff I make

[mitch5]

I would try to find one that is closest to the head gasket style(mls or graphite)you will be using. For my stock ej22 I used the factory head bolts along with the complex tightening sequence. After having a leaking gasket i got a set of arp studs. I would recommend getting arp if it’s in budget

[skills@eurocarsplus]

[vanis13]

[skills@eurocarsplus]

[valvecovergasket]

[vanis13]

[fxr]

The 2004 B sequence is just wrong in the book. It misses out the re-torquing between the loosen by 360 and the final 45+45.

Also remember to have the bolts well lubricated.
_________________
Jim Crowther
1984 1.9l EJ22 Westy Wolfsburg Edition
Vespa GTS 300

[skills@eurocarsplus]

[tencentlife]

TTY and TTA are the same thing: The process specifies a torque value, followed by an angular value. The process steps are torque-to-angle, the result is intended to be yield.

If the bolts you have were in fact torqued past their yield point, they should not be reused because after a second yield their full strength can't be assured.

We use TTY/TTA as a shorthand to refer to the fasteners, when theres no such thing as a TTY fastener. What there are are fasteners specified by manufacturers for specific assemblies and a TTY or TTA process is specified. But the fasteners aren't TTY until they've been yielded; up to then they could be used in a conventional process instead. But once they've yielded, they are no longer the fasteners you started with.

An application where TTA is specified is the shorthand indicator we use that those fasteners either will be TTY'ed or were TTY'ed. Even though not all TTA processes will result in yield, they almost always do because it's that process that was developed to be able to achieve a calculated and consistent amount of yield in all the fasteners in a grouping, in order that they are all left under the same amount of elastic tension afterward. If they didn't intend the bolt to yield, they would have almost certainly not specified a TTA process.

So when we see a TTA process, we presume it was to bring them to yield, and therefore we assume if they were used in that way, then they have been yielded.

There is a simple way to be absolutely sure, but it requires advance preparation: using special micrometer points for this purpose, record the fastener lengths when new, and again after use (one of the physical features that people point to to "prove" that a fastener is indeed a special TTY one is the conical recesses on either end, which most other bolts don't have. Those are there to enable accurate length measurements using the pointed mic adapters made to fit them). If it was yielded, it will be measurably longer, usually only a few thou but it is consistently measurable.

There are many fasteners for TTY-spec'd uses, rod bolts especially, where the manufacturer (ARP is really good about this) allows multiple reuses so long as a specific amount of elongation hasn't been exceeded, so all fasteners used in TTY apps don't necessarily have to be replaced every time, but without the elongation measurements and that usage data from the manufacturer, you have to assume they are elongated past an acceptable second use.

So, unless you have the exact lengths before use, so you can mic them and see if they have yielded, you have no way of being sure they have or haven't yielded. So, lacking that info, we assume out of caution that they have been yielded, and buy a new set rather than take the chance, because to be wrong with something like a rod bolt might cost the engine, whereas a new set is a known and fixed one-time cost (although they often cost quite a lot!). A head bolt failing would not likely destroy an engine, but breakdowns get costly fast, too, so it's the same old penny-wise / pound-foolish.

If you have bolts in hand that you know were used once and a TTA process was used on them, it's wise to assume they are already yielded. If you had the accurate original lengths you could actually determine if they were yielded or not. Lacking that, it's best not to take the chance.
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[vanis13]

[vanis13]

Ordered new OEM bolts. Will measure and compare them. I've come to trust Chris/tencent guidance. I'm thinking base of head to end of bolt or is there a different measurement?

For those interested...

An article by FelPro (big company) article indicating a difference in TTY and TTA

https://www.felpro.com/technical/tecblogs/tta-vs-tty-bolts.html

This ASE study guide 1) indicates tty bolts are common in head gasket applications and 2) have a diagram showing them reduced diameter shaft often associated with TTY bolts. The Subi bolts are constant diameter indicating they are not TTY (though they still may be)

https://www.freeasestudyguides.com/a1_4.html

Other than noticing the thinner center shaft section, there doesn't seem to be a consistent way to verify if a bolt is TTY by looking at it.

Taking to Chris, the following is not verification that it was right...but.... My last rebuild had no head gasket issue using old bolts for 50,000 miles

I like Chris' measuring idea/process and will post up the results.
_________________
83.5 Westy with Subaru 2.5, 4 spd manual, center seat, COLD A/C on 134a!, Winter camp heated with an Espar B4 gasoline furnace

www.SuperVanagon.com - some stuff I make

[wesitarz]

Subaru Mike on YouTube:"If a Subaru mechanic tells you he uses new head bolts he's lying."

and this:

https://www.youtube.com/watch?v=gOwu5nEet4c

[vanis13]

Yeah, I saw that MrSubaru1387 video which seemed to explain it well and his trove of videos makes it look like he knows what he's doing.

I like the measuring thing tencent suggested.... Maybe instead of waiting for my order, I'll stop by the Subi dealer to see if they have some in hand I can measure. The dealer parts guy I bought the new short block from said to reuse the old bolts and he was a mechanic rebuilding subis before transitioning to the parts department.
_________________
83.5 Westy with Subaru 2.5, 4 spd manual, center seat, COLD A/C on 134a!, Winter camp heated with an Espar B4 gasoline furnace

www.SuperVanagon.com - some stuff I make

[skills@eurocarsplus]

[vanis13]

Thanks a TON Skills! Your AllData screen picture corresponds to 2004 C. definitely helps settle concerns!

Turned out to be 2004 C (it is only by chance that it was C the last letter, I had no idea what order I was writing about them/putting them in.)

I'm just sorry for the folks that followed 2004 B with the missing info and may not have known better. 2004 A might have a chance.

.... So no AllData info on bolts it seems like? If I missed it somewhere let me know...I'm still gonna measure and report.

[skills@eurocarsplus]

[vanis13]

yep! there it is

thanks
_________________
83.5 Westy with Subaru 2.5, 4 spd manual, center seat, COLD A/C on 134a!, Winter camp heated with an Espar B4 gasoline furnace

www.SuperVanagon.com - some stuff I make

[wesitarz]

It's a no-brainer to use new MLS headgaskets.

[fxr]