Vr6 cylinder torque procedure-a bit wavy

[virtuoso23 10]

Ok so, put my rebuilt head on the VR,

 

Using standard torque to yield bolts

 

Torqued to: Stage 1 40nm Left for a day

Stage 2 60nm Left for another day

 

Come to do the 3rd stage which is two 90 degree..... walked in the garage and found my dad using the torque wrench on the head, I screamed....What are you doing..He say's torquing them up!!!

 

Anyhow after a lot of arguing I find instead of doing two 90 degree turns he's torqued them all up to a further 70nm

 

He say's there good!

 

I say we don't bloody know now!

 

Question is what do I do??

 

Are they past yield point, or below yield point?

 

Do i back them all off in sequence on re do to spec?

 

Or do I just give them all a 90 degree turn....

 

Stressing me out?

 

Half tempted to bin the lot

[a_riot 0]

Hmmm...what a bummer. Hard to really say since there is no torque spec for the TTY head bolts, only a procedure. Hard to believe someone would just come along and do that, considering how critical it is to get those head bolts tightened correctly. VR6 heads have issues with gaskets leaking through the cooling jackets at #1 as it is, leading to an over pressurization of the cooling system, so I'd be nervous not knowing where things are at. I think if it were me, I'd redo it all with a new gasket and new head bolts, since getting this wrong means major pain and misery. It might be fine, but knowing Murphy's Law, I don't think I'd chance it personally, especially since you just had the head rebuilt.

 

PS I think one 180 turn is the preferred method as opposed to 2 90 turns, but likely not a huge deal.

[Bauhaus 3]

Play safe and get new bolts as they could now be stretched just past the yeild point, although their now tight they may give gasket problems later on after a few hot and cooled down cycles on the engine use.

 

I guess your using once only use bolts as backing of and re torqueng will stretch them more on the final 90 degrees and wont clamp the gasket enough.

[virtuoso23 10]

Surely an extra 10nm is less than 1 x 180 degree turn or two final 90 degree turns......

 

The engine is out of the car, and everything is timed up now

 

Rebuilt head

 

New gasket etc

 

 

 

 

 

Can I get away with removing all bolts in sequence, throw them away and install new bolts without removing the head gasket?

Edited August 22, 2018 by virtuoso23

[fla 9]

Sorry if i'm being a bit thick here but is it now 70Nm or an additional 70Nm (ie 130Nm)? If the former, i would think that 2 x 90 degree turns would be much higher than an extra 10Nm.

[Bauhaus 3]

Assumption is a risky stratagy especially when 2 people have worked on the engine, for piece of mind get new bolts, not worth guessing what the torque is at now, Changing bolts one at a time (with the others still in place) can be done in the correct sequence up to the stage 2 torque settings.

 

If you have a digital torque wrench you can check what the torque was by using the peak tracking setting by slighty backing one of the bolt off and noting the readout.

[swiftkid 1]

Sorry if i'm being a bit thick here but is it now 70Nm or an additional 70Nm (ie 130Nm)? If the former, i would think that 2 x 90 degree turns would be much higher than an extra 10Nm.

 

No, its just 70Nm so an additional 10Nm. Same way if you torque it to 70Nm and then retorque it to 70Nm you wouldn't then get 140Nm, it would just click straight away. You can get all the advice but unfortunately it's down to you whether to change or not, my mate once misinterpreted the torque settings on a 9a (2.0 16v), it said 180 (90), 180 (90) - as in 180 degrees, back 90 and instead went 180, then another 90. I genuinely thought they were going to snap but turned out to be the most reliable engine out of all of us.

 

As long as you don't remove the head you could probably get away with loosening them all up in sequence (leave them just over finger tight on the safe side) and then replacing.

 

Does your dad not remember how far he went with each?

[virtuoso23 10]

Hey guys, yes I can confirm he went an extra 10nm from stage 2 at 60nm in sequence, hes not inexperienced. I have gone over all bolts and to be fair to him all of them click exactly at 70nm.

 

Maybe I could go two 80 degree turns instead of the two final 90 degree turns.....

[vw rule 19]

I wouldn't back off the bolts now that they have been torqued up, as the head gasket is now compressed, ok it's not fully compressed yet but you're only supposed to use the gasket once.

If you're 100% sure that the total torque value is 70Nm that's been applied so far to the head bolts, then in theory you should be ok to complete the last stage.

An extra 10Nm is minimal it's only 4 to 5 degrees if that anyway.

So you can apply 180 degrees dead on the mark I'm sure it'll be fine.

 

Si

[virtuoso23 10]

I'll give this ago then.

 

I'll do a 90 degree, then the final, maybe on the last go in at 80-85 degree

[vw rule 19]

I wouldn't go over 180 degrees or any less than 176 degrees on the last stage.

This is purely going on what you've told us that an extra 10Nm of torque was applied on the second stage.

 

Note!

If you have any doubts at all regarding how much net total of torque, was applied on stages 1 and 2 then start again with a new head gasket and new head bolts.

 

Si

Edited August 23, 2018 by vw rule

[virtuoso23 10]

No doubts on the extra torque, 10nm across all 20 bolts after stage 2 at 60nm.

 

I'll give them all a 176 degree turn then

[vw rule 19]

Yeah like I say I'd turn them 180 degrees max no more, or 176 degrees minimum, going on what you've said regarding torque settings.

You can mark the head of the bolts with a bit of white tippex for stage 3, so if you get distracted by a phone call, you'll see which bolts were turned.

That's what I do when tightening down head bolts.

Plus I always do an extra degrees just to be safe, so if I had to turn head bolts by 150 degrees, I'd go 152 degrees max there's enough elasticity in stretch bolts for + 1 or 3 degrees.

 

Si

[virtuoso23 10]

Many thanks for your advise Si, good information and feel more confident going forward now. I will indeed mark the bolts as you have said.

 

Fingers crossed

 

Will update this weekend after attempting final stage

[Bauhaus 3]

Were the bolt threads oiled or dry prior to torqueing ? ... Makes a big difference in the torque to yeild point, But equating degrees of rotation to estimated torque is a gamble just like doing a few more degrees for luck.. go by the official settings and not by hearsay.

Marking all torqued up bolts is good engineering practice.

[virtuoso23 10]

Yes I did add a smear of oil to each bolt prior to installing. Then as per factory guide line followed stage 1 then stage 2.

 

The guide say's to go from stage 2 to 180 degree or two 90 degree turns, but thats from 60Nm.

 

I'll be going from 70Nm, so wouldn't going the full 180/ 2 x90 be a tad over spec or yield......

[a_riot 0]

Yes I did add a smear of oil to each bolt prior to installing. Then as per factory guide line followed stage 1 then stage 2.

 

The guide say's to go from stage 2 to 180 degree or two 90 degree turns, but thats from 60Nm.

 

I'll be going from 70Nm, so wouldn't going the full 180/ 2 x90 be a tad over spec or yield......

 

I don't think you can calculate it that way. In theory, the bolts start to stretch once the first 2 stages are complete. So if they were tightened up to 70nm after stage 2, they've already started to stretch some. Typically you don't reuse a TTY bolt once its been stretched, which you would be doing if you now do a ~180 rotation. Its not the torque value you need to worry about, its the stretching of the bolts, which is why the 180 turn is preferred to 2 x 90. If it made no difference, instead of one 180 turn like Mr Bentley says, you could do 4x45 degree turns, or 8x22.5 degree turns. But that isn't recommended with stretch bolts. You can likely get away with it if the bolts didn't stretch at all when tightened to 70nm but I can't think of a way to tell after the fact.

Edited August 23, 2018 by a_riot