TTY head bolts - more than you might want to know.

[TylerDurden]

Also, the bolt is stretched one full turn or 1.75MM, leaving 9.25MM

FWIW, The "original" bolts I pulled from my '91 were only stretched .875mm. Not even 1/2turn.

Which correlates, if the first turn to angle is 180 (or two 90s). Some folks don't bother with the followup turn after a heat/cool cycle.



- edit to include quote -

[745 turbogreasel]

Were you able to measure them with the head installed? or is this after they had relaxed again?
Some of that will be in compression of the head gasket  rather than bolt stretch I suppose.

[TylerDurden]

Lol, the bolts were out.

But a fair question... how much do they contract... I would say the tension was off after turning them out 1/4turn (some much less). What percentage of that was gasket and how much was the elasticity of the bolt,  how much was loosening over time... who knows.


I can say with certainty that the first try with DRY bolts, three yielded on the first 1/4 turn. They were the ones I remarked were shinier than the others... maybe the threads were rolled after the oxide coating was applied.  The rest were identical length to new.



IIRC, they were longer by... 1/4 turn.

[745 turbogreasel]

As a casual observation, steel will spring back about half way from bending in plastic range...straightening body and frame panels is an easy place to see this.
Taking this as a general rule, 1/4 thread of stretch would be perfectly consistent with your having skipped half of the tightening procedure.

[bbob203]

* note to self buy head studs...?

[92EcoDiesel Jetta]

As I recall when I did the head gasket on my 92 Eco more than a year ago, I tried to measure the old bolt's stretch compared to a new bolt (from bottom of bolt head to tip of bolt) and the difference was so small it was not measurable with a vernier caliper. The only way to tell if there was bolt stretch was to place the threads of an old bolt against threads of a new bolt, held up to sunlight so you can observe the slight uneven meshing of the threads.

[TylerDurden]

Ja, that's how I did it too... not even a half thread difference on the old bolts compared to a new.

[R.O.R-2.0]

not so BIG of a puddle is necessary to push thru block, theres not alot of space between bottom of bolt and block, and bolt seals at block if even 1 thread up the bolt, you wont need a lot of LIQUID to do it.
in any case the main thing is cleaning holes w/brake clean everytime. And make sure all brake clean is dry too.

1.5D and 1.6D head bolts dont come anywheres close to bottoming out in the block with the head, gasket, and OEM bolts in place..

 

wtf you talking about?

you need a visible puddle of liquid at the bottom of the threaded hole.

[TylerDurden]

* note to self buy head studs...?

I'll pass on studs. This is a one-shot. (I hope)

Plus, I'm pretty sure the dings in the head surface were from the PO using cut-down bolts when replacing the head, but struggling to line it up with the manifolds on.  Certainly wasn't wood dowels that marked up a freshly machined head.

[air-cooled or diesel]

not so BIG of a puddle is necessary to push thru block, theres not alot of space between bottom of bolt and block, and bolt seals at block if even 1 thread up the bolt, you wont need a lot of LIQUID to do it.
in any case the main thing is cleaning holes w/brake clean everytime. And make sure all brake clean is dry too.

1.5D and 1.6D head bolts dont come anywheres close to bottoming out in the block with the head, gasket, and OEM bolts in place..

 

wtf you talking about?

you need a visible puddle of liquid at the bottom of the threaded hole.

who are you in the first place, and i dont understand why you would take this for granted, its not bad advice in anyway. if you pull your head you need to be aware of this, it cannt hurt in anyway; and might i say IS on topic

[R.O.R-2.0]

not so BIG of a puddle is necessary to push thru block, theres not alot of space between bottom of bolt and block, and bolt seals at block if even 1 thread up the bolt, you wont need a lot of LIQUID to do it.
in any case the main thing is cleaning holes w/brake clean everytime. And make sure all brake clean is dry too.

1.5D and 1.6D head bolts dont come anywheres close to bottoming out in the block with the head, gasket, and OEM bolts in place..

 

wtf you talking about?

you need a visible puddle of liquid at the bottom of the threaded hole.

who are you in the first place, and i dont understand why you would take this for granted, its not bad advice in anyway. if you pull your head you need to be aware of this, it cannt hurt in anyway; and might i say IS on topic

does it matter who i am?

i DO know that you give BS advice over at the whoretex all the time..

you should never install or torque your head bolts DRY..

i know my VW engines.. and how far the head bolts thread into the block..

[8v-of-fury]

Language and Aggression check please. Leave it at the door, it need not apply here.

[TylerDurden]

I got a reply from Victor Reinz - GmbH. 

07.12.2012 20:44

Hello,

Should new headbolts be lightly oiled, specifically, for Volkswagen  TDI and IDI engines?

The Robert Bentley manuals for Volkswagen  TDI and IDI vehicles are unclear regarding whether new headbolts should be oiled (or dry) for installation.

The Victor Reinz literature indicates generally they should be oiled (but also indicates to follow manufacturers' directions).

Any help to clear this ambiguity is appreciated.


Thank You,

T. Durden

[R.O.R-2.0]

i rest my case... ^^^

NEVER install bolts DRY..

i go one step further, i use copper anti-seize, or pipe thread sealant on ALL the head bolts i re-install..

if the bolt goes into the water jacket, then it gets PTFE compound just for extra help. ive had toyotas leak from the head bolt holes.

[burn_your_money]

i go one step further, i use copper anti-seize, or pipe thread sealant on ALL the head bolts i re-install..

You re-install headbolts? Dude, this whole thread is about replacing them