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

[burn_your_money]

Because it is an angle torque it does not really matter if you oil them or not. 180 degrees is 180 degrees whether the threads are dry, coated in 30w or coated in peanut butter. This is the exact reason why most OEMs spec angle torques for critical areas. It eliminates a lot of potential error.

[745 turbogreasel]

NO, you do NOT oil stock head bolts!

There is a reason you angle tighten them and not torque them to a certain number. Torquing them to only 44ft-lbs then angle tightening eliminates most of the friction error. DO NOT OIL
Un oiled threads like to gall up.

If you oil head bolts you'll only get about 80-110ft-lbs out of them, if you try for more you'll just stretch the hell out of them... My haynes manual says to oil them, Bentley says DRY! Bentley is correct. Bolts with oiled threads stretch more easily?

I am experimenting with something new, I use 12.9 SHCS, M12x1.75 by 110mm long, 115-125ft-lbs OILED(30w oil).  pick your torque and use the same torque for all of them. Make sure to clean the holes out very well, sucking out any fluid that is in them to prevent cracking the block.

It eliminates a lot of potential error.

Or sells a lot of one use bolts.

That said, buy studs once, your head wont lift regardless of torque, and you will never have to buy another one.

[burn_your_money]

Just because a bolt has an angle torque does not mean it is 1 time use. In the case of our headbolts, it most certainly does mean 1 time use however.

You have to blow a lot of headgaskets to make studs financially worthwhile.

[libbydiesel]

Just because a bolt has an angle torque does not mean it is 1 time use. In the case of our headbolts, it most certainly does mean 1 time use however.

You have to blow a lot of headgaskets to make studs financially worthwhile.

Well, that depends on whether or not the headgasket is more or less likely to blow with studs.  If the head gaskets lasted the exact same amount of time with studs vs stock bolts it would take 10 blown gaskets to pay for the studs (never gonna happen unless you are really abusing your engine).  If, on the other hand, the studs double the lifetime of the gasket, they will be more cost effective on the first gasket as the labor to swap the gasket is more than the initial cost of the studs. 

[TylerDurden]

If you read the lit, you will see that friction error is not reduced by torquing into the elastic range. In the case of these headbolts, the two torque stages bring the fastener past the alignment-range and ensure that the bolt gets near or past the elastic range; usually into the plastic range (yield).




The critical issue is clamping force, you can be reasonably certain that the clamping force is adequate when friction losses are minimized. Quite the contrary, if friction is increased.




The Haynes and Bentley manuals I have here (two mk2, four mk1) do not say bolts should be "dry", only that the block threads should be chased and free of debris.

Lube selection is more critical with studs, as they have no yield to prevent over-tightening.


I spoke with a guy yesterday who has done a couple hundred heads, who concurs bolts should be lubed.

[745 turbogreasel]

Just because a bolt has an angle torque does not mean it is 1 time use. In the case of our headbolts, it most certainly does mean 1 time use however.

You have to blow a lot of headgaskets to make studs financially worthwhile.

Well, that depends on whether or not the headgasket is more or less likely to blow with studs.  If the head gaskets lasted the exact same amount of time with studs vs stock bolts it would take 10 blown gaskets to pay for the studs (never gonna happen unless you are really abusing your engine).  If, on the other hand, the studs double the lifetime of the gasket, they will be more cost effective on the first gasket as the labor to swap the gasket is more than the initial cost of the studs. 

Also if you are the kind of person who might remove the head for another reason before the gasket blows.

[theman53]

If you oil head bolts you'll only get about 80-110ft-lbs out of them, if you try for more you'll just stretch the hell out of them... My haynes manual says to oil them, Bentley says DRY! Bentley is correct.

80 to 110 is about all you get when you angle them. FWIW you are wrong, if you oil the bolts the coefficient of friction is reduced and you will torque the bolts more not less. Your torque wrench will click later as it will be going off more the clamping force than friction, then you will go off angle from there. It won't be much as you are only talking 44 lbs, but still.

Watch out how long your SHCS are. You can crack a block if they are too long and I thought the one guy from Kansas said 105mm was the limit. Also, I sell bolts for a living and McMaster is competition...most all of the SHCS they sell are from China or Taiwan.

[JFettig]

Wow, lots of misinformation.

I'm wrong about something you interpreted different then intended? oh well.

As a mechanical engineer who designs bolted connections on a regular basis, I have a little bit of an idea whats going on here Oiling the bolts increases the load on the bolt at 44ft-lbs torque, thus increasing the load on the bolt at +180 degrees. For these bolts, it runs them farther into yield and closer to ultimate, maybe even past it where clamping force drops off.


If they gave you a spec for oiled bolts, it would be the correct way to torque them, they gave us a torque spec for DRY bolts, torque them dry.

I didn't willy-nilly grab 12.9 bolts from McMaster. FWIW, I used these on TDI's, I dunno if its any different than TD's, but with thick hardened washers it brings it up to about 107mm.

Not all Chinese stuff is garbage. Maybe these are lesser quality than your product, maybe not. They're working great so far at 200hp/300ft-lbs. Moving up to ~220/350 soon.

[burn_your_money]

80 to 110 is about all you get when you angle them. FWIW you are wrong, if you oil the bolts the coefficient of friction is reduced and you will torque the bolts more not less. Your torque wrench will click later as it will be going off more the clamping force than friction, then you will go off angle from there. It won't be much as you are only talking 44 lbs, but still.

Oiling the bolts increases the load on the bolt at 44ft-lbs torque, thus increasing the load on the bolt at +180 degrees. For these bolts, it runs them farther into yield and closer to ultimate, maybe even past it where clamping force drops off.

Pretty sure you guys are saying the exact same thing 

[92EcoDiesel Jetta]

I agree oiling the bolts will result in advancing the bolts further than if they were dry during the torque wrench sequence (30, 44, 55 ft lbs), and will end up with higher torqued bolts after angle torque. The Bentley I have does not state (or I have not found it yet) whether the head bolts should be oiled or dry. If anyone find it, please post the section and page.

JFettig, which McMaster 12.9 bolts did you use?

[TylerDurden]

... they gave us a torque spec for DRY bolts, torque them dry.

No mention of dry bolts in any Haynes or Bentley i own.

Victor Reinz specs lightly oiled.


http://www.reinz.com/pictures/39-00129-10_PI_2_Bolts-low-e.pdf

[JFettig]

Bentley doesn't say TO oil them, Every TDI mechanic I've talked to says DRY DRY DRY. This is including Franko6 and others.

#10, IF the manufacture specifies....

92EcoDiesel Jetta - previous page, last post.

[92EcoDiesel Jetta]

NO, you do NOT oil stock head bolts!

There is a reason you angle tighten them and not torque them to a certain number. Torquing them to only 44ft-lbs then angle tightening eliminates most of the friction error. DO NOT OIL

If you oil head bolts you'll only get about 80-110ft-lbs out of them, if you try for more you'll just stretch the hell out of them... My haynes manual says to oil them, Bentley says DRY! Bentley is correct.

I am experimenting with something new, I use 12.9 SHCS, M12x1.75 by 110mm long, 115-125ft-lbs OILED(30w oil).  pick your torque and use the same torque for all of them. Make sure to clean the holes out very well, sucking out any fluid that is in them to prevent cracking the block.

http://www.mcmaster.com/nav/enter.asp?partnum=91290A642
http://www.mcmaster.com/#98035A107

Are these Mcmaster bolts multi-use? They're not listed as TTY so I assume they are not one time use. Not bad, $20 for a set of bolts and washers! They are Allen, not XZN?

[JFettig]

At that price I'd replace them. they are 10mm allen.

[libbydiesel]

That's like $130 for the hardware that you still consider single use.  I'd just buy the stock bolts or the ARP studs. and not mess with an experiment that costs 10 times what the stock bolts cost.