Snapping head bolts

[Johnanthony 3]

Why do I keep snapping head bolts? First I snapped an old one, so I bought a complete new set and snapped one of those too. I used a different torque wrench each time, so that should not be the issue. The nub is not bottoming out because it is loose when I pull it back apart to dig it out (I also measured the depth). I have not run a tap down the well to clean the threads yet as I don't know what size to use. That will be my next step.

[Johnanthony 3]

it's a 4.1L 250 xflow injected on gas.

[revhead 1,392]

also make sure you suck any oil or water out of the head bolt holes as you cant compress water,also make sure you can wind one in by hand before it bottoms out on bolt hole,

[slydog 7,873]

And your on your chosen torque rating...not doing it in nm where it should be ft lbs if you get my drift.

 

I have never snapped a xflow bolt but did brake a ohc bolt.

[Johnanthony 3]

Yeah I cleaned all of the gunk out with little cotton buds. Wound them all the way in by hand then proceeded to snap the bolts before the tourque setting engaged. I want to run it with a tap, but I don't know which one to use.

[revhead 1,392]

are you snapping the same head bolt ,

[Johnanthony 3]

The first time I thought it was a stuffed tourque wrench. That was with the original bolts. I ordered a duropro set and borrowed a different wrench. And snapped another bolt today. Just want to get it right this time. Pretty embarrassing that I have to put the head on a third time now.

[Johnanthony 3]

First time was the 10th, today was the third.

[revhead 1,392]

have you checked the length of the old vs the new bolts

[Johnanthony 3]

Bolts are all the same length, and the wells are a lot deeper than the bolts.

[Mr Polson 10,214]

Someone on here snapped one due to using the wrong measurement (NM instead of ft lb.), like Sly said are you using correct measurement?

[Johnanthony 3]

Rookie mistake, try setting the thing to 98nm only on the £ft side and the thing is not going to work properly. I checked I wasn't that stupid already, yet I don't think many ppl could torque 102£ft by hand. It does feel like the bar is not working properly though. I have been using an extension wobble bar both times and I think that may be affecting reading.

[FORD_MAN 1,026]

Maybe time for studs, what did you have to remove the head for?

 

EDIT we posted seconds apart.. ft/lb instead of Nm explains a bit.

And yes the extension bar twists under load, I use Impact sockets & extension bars when I can.

[Johnanthony 3]

Overheating. Exhaust leak

[Ando81 2,949]

Someone on here snapped one due to using the wrong measurement (NM instead of ft lb), like Sly said are you using correct measurement?

That loser was me mate

[wagoon 2,429]

How much was shaved off the head to get it square?

[Outback Jack 6,352]

It will be from using Foot pounds measurement, which is tighter than Nm. The head bolt specs are in Nm for Fords.

It's sometimes easy to do, for some god unknown reason they put Foot Pounds on the torque wrenches on the side you look first and Nm on the reverse, none of them use different colours or something to make the two look different (hint, hint tool makers).

We used to grab a chicks nail polish or some model paint and fill the letters on each side with a different colour....... helps.

 

Jack.

[slydog 7,873]

I have a Fubur torque wrench and both measurements are next too each other and TBH I have set it on the wrong scale once but noticed it straight away as it took like 400 turns to set it which proved the mistake.

 

As my other post I belive it was the wrong measurement used like Ando said as it prob the only possible way it can happen if,he has wound em in by hand with no issue then breaks em with the wrench. Still it would take ALOT to break one as there pretty strong I'd suggest you would be thinking your doing it up tighter than normal.

[Mr Polson 10,214]

It will be from using Foot pounds measurement, which is tighter than Nm. The head bolt specs are in Nm for Fords.

It's sometimes easy to do, for some god unknown reason they put Foot Pounds on the torque wrenches on the side you look first and Nm on the reverse, none of them use different colours or something to make the two look different (hint, hint tool makers).

We used to grab a chicks nail polish or some model paint and fill the letters on each side with a different colour....... helps.

 

Jack.

 

They put foot pound on the front because that's what torque wrenches are calibrated to, then the NM is added on the other side.

 

Ever notice the ft lb side is always exact numbers but the nm is normally random 1-9 and then decimal points.

[Johnanthony 3]

Thanks for the posts guys. I am positive I set the wrench properly. Even had my cousin check it at the time, so we can't both be wrong ( I was borrowing his wrench).

What baffles me is that a wrench set to 60£ft should click well before I am able to snap the bolts. Obviously I am using the tool incorrectly. I think it is because I was using an extension bar between the socket and the wrench.

[Johnanthony 3]

Would this happen if I have a warped head?

[Outback Jack 6,352]

I dunno mate, most of us here are a bit warped in the head but it doesn't affect our mechanicals............ LOL

 

Are you any closer to finding the problem?

 

Jack.

[Johnanthony 3]

Ha ha pretty funny.

So I guess the extension bar causes a mis read on the torque wrench.

Ever heard extension bars called a torsion bar? This is because the property's of steel allow flex, or in this instance torsion. Therefore when measuring torque at a slow controlled pace, the bolt has reached its desired maximum setting long before the actual torque reading on the wrench has engaged. This is because of the torsion inertia effect is a reduction in torque force applied. So much so that I was able to snap bolts with a precision torque wrench set on a low setting. Before the wrench engaged. Mind blowing.

Works in reverse too. When tightening bolts by hand the maximum amount of torque possibly applied to a bolt is less when using a torsion bar.

Thanks for all the support. When Lady Luck turns and smiles in my direction. When I stop making stupid mistakes, when I make a decent amount of progress... I will remember all the support and upload some photos.

 

The build is an 84, Xf ute

250 xflow

Injected gas

Lukey high flow system

Aussie four on the floor.

It has been a long and slow process as obviously I am stupid or crazy and don't know what the hell I am doing, and this vehicle has lived the hard life. Just like an Aussie ute should.

Long live Aussie fords.

[wagoon 2,429]

The onl way to learn is from mistakes, they are only stupid mistakes if you make them again.

On a side note have you had the head machined flat? You said it had overheating problems, did it get really hot really quick or all of a sudden? Did the headgasket blow? Only ask as there is no point putting the head back on if you havent had it machined.

[gerg 10,871]

Must say in my 20 years as a mechanic I've never broken a bolt by using an extension bar on a torque wrench. Torque is a rotational force, and your extension bar simply becomes a torsion spring. No big deal, as a spring just stores energy. You just have to move the torque wrench a bit further to get to your setting.

 

I'll equate it to weight. Instead of a rotational force like torque, weight is a linear force as a result of gravity. If i put a set of scales on the floor and stand on them, i weigh 77 kg (on a good day). If i then put the scales on a bouncy latex pillow (ie a spring), i don't suddenly weigh more or less. I still weigh 77 kg but it takes a certain amount of compression in the "spring" to reach my weight.

 

Your torque wrench is nothing more than a scale that clicks off at a certain force. What you have attached to it is immaterial.

 

I must read more about this torque inertia thing.

 

The only way i can see an extension bar being a problem with torquing bolts up is when you're using the "angle torque" method, as used with E-series engines. Even at that, it will be less torque, not more.

 

A couple of questions: were the bolts of decent quality? Did you use lube on the threads and under the heads? Did you do the torque-up in stages? The more stages the better. I like 3-4 stages myself, starting at 1/3 of the max setting.