EJ head bolts - how many times can they be used?

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El_Freddo
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EJ head bolts - how many times can they be used?

Post by El_Freddo » Mon Jul 08, 2019 7:58 pm

As the title suggests, how many times can the EJ head bolts be used before it’s recommended that new ones be used?

Obviously if the bolts are rusty, heat stressed (overheated) or the threads are damaged they’re to be replaced.

I’ve got my sister’s EJ251 on the engine stand to replace the HGs (external coolant and oil leaks). This will be the second time I re-use the head bolts. The dude at the engine machine shop has me second guessing myself with a comment he made about the bolts stretching to a limit.

I’m not wanting to do this job again in another three or four years (or months if the bolts are dud)! This EJ251 is awesome to drive - I’ve got a soft spot for the EJ251 and probably the EJ253 too since having this 251 in the family.

Thoughts/opinions appreciated!

Cheers

Bennie
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Subyroo
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Re: EJ head bolts - how many times can they be used?

Post by Subyroo » Mon Jul 08, 2019 8:28 pm

Myself being pedantic, I'd use new head bolts to save having that nagging feeling in the back of my mind.

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TOONGA
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Re: EJ head bolts - how many times can they be used?

Post by TOONGA » Wed Jul 10, 2019 4:51 pm

Bennie the bolts are not stretch limited but they should be replaced if this is the second time they have been used.

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El_Freddo
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Re: EJ head bolts - how many times can they be used?

Post by El_Freddo » Thu Jul 11, 2019 4:30 pm

You mean the second time they’ve been reused?

I’ve reused these once already - and it turns out there’s two different types of bolts for the EJ251, the two inner bolts are different to the outer bolts.

I didn’t know this and had them where-ever they were randomly placed... no issues.

I’ll have to see if I can dig up the Subaru tech bulletin talking about the head bolt reuse. Problem is that I can’t remember where it was shared publicly.

Now that I have the heads back, I’m not in any rush for the head bolts as I’ve decided that I’ll replace the valve stem seals and lap the valves if needed.

The dude who shaved the heads gave me a good piece of advice - always retorque the cam retainer bolts once the headbolts are installed and up to torque. This could also explain why the EJ251 typically has a small leak from under the cam retainer plate, even though it’s sealed by silicone like three bond or that high torque application sealant.

Cheers

Bennie
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Suby Spanner
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Re: EJ head bolts - how many times can they be used?

Post by Suby Spanner » Thu Jul 18, 2019 10:39 pm

Basically the 'general' rule is any bolt that is angle tightened (eg. Xft-lb, then 60 degrees, then 60 degrees) are "torque to yield" and should be replaced each time. Torque to yield is a whole nother topic, and you can lose hours if you start googling and reading about it.

Now, there are some exceptions, some manufacturers give a spec it's either overall length of the bolt, or if the bolt has become skinnier along it's shank after use.

AFAIK, Subaru are replace every time. That said, I worked in an importer for a while, we imported hundreds of suby engines, mostly from front hits, they always spit the belt and bend at least one head's valves. So we'd often make one good engine from two, and sold the remaining bottom end (short block) to the local suby specialist who liked busting customer cars on their dyno (how they become a specialist is beyond me).

Not once did any of those engines come back with leaks, and we never replaced the bolts.

When I do a customers car I always replace bolts if they are available aftermarket, the general rule there is if they are listed, then they are torque to yield, and for the same cost as half an hours labour, just replace the damn things.

*shrug* Dunno, for me, I don't have enough time to do job's once, let alone twice, so I'd never skimp out on bolts on my own stuff... You might be in a different position though... That said I have had 2 engine have head bolt failures upon assembling: One was a falcon, and the damn bolt broke as I was torquing it up, that wasn't fun at all. The second was a Nissan engine, I was torquing, and torquing and torquing, and this one bolt got easier and easier to turn, I thought something wasn't right, so I pulled it out, it was starting to look like a long hour glass! It has stretched that much, and that was a brand new torque to yield bolt, so go figure! And, yes, my torque wrenches are regularly calibrated.

Would you have an instant failure from reusing the bolts? Doubt it. But don't blame me if you do....

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