engine and drivetrain Tightening --- The Torque And Angle Method.

[allbim]

I don’t care what the manufacturers say. 

The torque and angle procedure for mounting a cylinder head is BS.

Picture this:  You are tightening the head-bolts, working your way from the center of the head out towards the ends.  The center bolts are tightened to their final position, but as you tighten the rest of the fasteners, the gasket gets squashed more and more.  By the time the outer bolts are properly torqued , the center bolts will be loose again.  How is this supposed to work?  I can see that the “torque and angle technique” might work when there are no gaskets involved that can collapse; such as bearing caps or other metal to metal applications, but not with squishy gaskets.  Am I missing something?  

 

Added on 10/28/13

The torque and angle method was devised to minimize bolt tension variations caused by variations of friction in the sliding surfaces, caused by differences in lubricants, the amount of lubrication and the type of materials sliding against each other.

Edited October 28, 2013 by allbim

[Tommy]

You can think the other way around. I think this is how it should be.

You torque first lightly, so that gasket is tight but not squished yet. Then turn each bolt same amount. Shouldn't that be pretty even then?

 

After writing that, I still like the old simple method more. In last assembly I tried the angle method first time and I think the bolts went way more tighter than with the old method. I'm interested to hear what the real specialists say.

 

  Tommy

Edited October 28, 2013 by Tommy

[Napes]

Here's some info I received from Tom Jones, who's been working on '02s in the shop where he works for many years.  First is my questions to him:

 

"My question regards weather I can use the the old head bolt torque values upon reinstalling a new gasket (and I'm using new head bolts this time). I'd use an initial torque of 25-33#/ft., wait 15 min., torque to 43-47#/ft., run the engine 25 min, then a final torque of 49-52#/ft. (though I've heard thah 55#/ft is good for the final torque)."

 

And here's his reply:

 

"Yes you can use the old torque specs... . I've successfully used both old and new specs. And a reminder to readjust the valves after whatever last torque. I used to ramp up to a final of 60lbft. Make sure there's a light coating of oil on the bolt threads and holes. I usually only blow out the holes with compressed air and a couple drops on the bolt threads."

 

Current head gasket has been in for about a year with no problems whatsoever.

 

Bob Napier


 

[KFunk]

I say the angle torque method is BS as well.  I did all the recommended things and followed the procedures on my new engine, cleaned out threads well, new bolts with oil on them, etc.  Within 300 miles, compression started leaking from cylinder to cylinder, and then it blew a big hole in the head gasket.  Not gonna do that again.

 

Not to mention, with the angle torque method, there's no way to easily re-torque the head bolts after the engine has been run a little.  You can't just snug them up, you'd have to loosen them all the way and go through all the steps again.   

[allbim]

As KFunk hints, you could of course go through the tightening procedure more than once, loosening one bolt at a time and then re-tightening it, using the torque/angle method. This obviously cannot be done with stretch-bolts, but M10 head-bolts are not stretch-bolts.

Edited October 28, 2013 by allbim

[TobyB]

 

I've successfully used both old and new specs.

 

Me too.  Having gone through a bunch of head gaskets in a short time (because racecar) you start to figure out that both methods

are supposed to crush the head gasket to a certain thickness, and thus, compression pressure.

 

With the angle method, if you go too far, there is a 'torque step' that you feel (it can be measured- it's about 80 ft/lbs) when you

get to a certain point.  That's where the head gasket 'bottoms' on the hard surfaces in it (inside the fire rings at the cylinders).

When you hit it, it feels like the bolt has stopped- yes, maybe you could go further, but the 'mechanic's sense' says that you'll probably

bend or strip something.

 

I think the idea with both methods is to get you CLOSE TO, but not ONTO, those hard surfaces.  Leaving just a little bit of 'give' in the

head gasket flexible materials, but not much at all.

 

What I found.

 

t

[Pamola]

Allbim,

 

You second comment is correct. Torque plus angle is used because otherwise with torque only the friction of the head bolt threads against the block threads gets mixed into the torque reading (yes even when oil is applied). Since the goal is a uniform clamp load torque + angle is a better approach.

 

To get around compressing gaskets reducing the torque load (at least one) manufacture recommends doing the torque + angle in 3 passes. So you would turn each head bolt 3 separate times. A more precise name for the procedure might be torque + angle + angle.

[TobyB]

...they all do that...  initial torque, add initial angle, add second angle, sometimes heat cycle and add more angle.

 

 

t

[Stevenc22]

Bump an old thread.

 

The heat cycle between the first and second angle. Do you let the motor cool after the heat cycle before retightening or do you tighten a hot motor?

Edited May 9, 2014 by Stevenc22

[TobyB]

Ha.  I have often wondered that.  Except that it says to heat the motor, then add angle.  So you  twist while hot.

If you were supposed to  rotate cold, it would have an extra 'go down twelve steins, and then sleep it off' step.

 

The difference between German and 'other' thinking.

 

Honestly, I expect it doesn't matter too much, except that you get a 'hot torque', and if you do that with the

'traditional' method, you almost always end up adding 45- 90 degrees on each bolt.

 

Clear as mud?

 

t

 

edit- oh, yeah, as Buckeye says, it's between step 4 and 6 that you warm it up.

 

1- initial torque (30 ft- lbs from memory, but that's got holes in it.  Too many cars.  Too many GinandTonix)

2- add some angle

3- wait

4 add more angle

5 add heat

6 add even more angle.

7 profit

Edited May 10, 2014 by TobyB

[Buckeye]

Bump an old thread.

 

The heat cycle between the first and second angle. Do you let the motor cool after the heat cycle before retightening or do you tighten a hot motor?

There is only one warm cycle. Not two. First time torque to 60 Nm, then wait 15 minutes and torque angle to 33deg. Next step warm up the car to normal temp. Torque angle to 25 deg.

[Cyclone101]

You can, but it can be torqued hot as well according to elring at least.

[DaHose]

I've never built anything up that called for torque angle, but I also don't work in aerospace.

 

My take would be that if a straight torque reading is good enough to keep the S38 in my M6 (or an M88 in an M1) together, then straight torque is good enough for me.

 

 

Jose

[Buckeye]

Aerospace is not the only industry that uses torque and angle. Other industries like under carriage manufactures for class 8 heavy truck use torque and angle to fasten carriers to drive axle housings.