Can someone explain what "Angle Tightening" is? (Searched)

[Deadeye 5.1]

So when reading the FSM it warns against standard torque setting and instead tells you use an "angle tightening" method(this is for the head and rod bolts). What the hell?? Could someone explain this? I feel stupid now...

[WAbernethy]

I believe it's when you tighten a bolt until it's snug (highly technical term) and then crank it hard by some angle. Usually 45 or 90 degrees. Spark plugs are usually installed this way. I've never heard of tightening head bolts this way. Usually you torque them in several different steps. ie: 45lbs, 60lbs then loosen them and torque to 45 and then to 80 or whatever it is.

[Nathan]

This is definitely the fsm method of installing headbolts, you use standard torque settings to go through a staged process as abernethy described but then you bring them to a certain lb.ft. level and finish them off by "angle tightening" them by 90 degrees. In other words, it goes something like 30lb.ft, 60lb.ft, 45lb.ft, 90 degree turn. However, its not those settings exactly, thats just an example.

[Deadeye 5.1]

Ok, thats simple enough. Maybe I didnt read the FSM carefully enough, but it seemed kind of cryptic...

Thanks!

[Nathan]

Yeah, I should also have explained the reasoning behind it. Torque settings can sometimes be inaccurate because of friction between the bolt and the hole it threads into, as well as the head of the bolt and its mating surface. The thinking behind angle torquing is that you bring the torque up to a certain level where the lb.ft. setting can still be accurate and then by angle torquing it, you will get a very precise amount of torque in the end. Things will be more uniform, and less likely to be loose The only methods that would usually be more accurate would be studs, or actually measuring the bolt stretch (not always possible obviously).

[TrunkMonkey]

in a nut shell, the reason for using an angle wrench to tighten cylinder head and connecting rod bolts is to pre-stretch the bolts.

if you don't use an angle wrench, or follow the procedures in the FSM (torque, loosen, then retorque to higher specs) to stretch the bolts, then the combustion process (head bolts) or the tensile load (rod bolts) will do it for you...and that's not a good thing.

-demetrius

[erich]

Remember that the head bolts are ment to stretch a certain amount. With the pitch of the threads you can know exactly how much the bolt stretches by how much you turn it. I just use a good click-type torque wrench and call it a day.

[WDRacing]

On the helicopters I work on, we torque everything. On critical fasteners with a lareg amount of torque, like the head bolts, the bolts heat up and stretch as the bolt had a load applied to it. So the tech data says to retorque the bolts again after 1/2 hour of cooling down period. We also make sure each bolt is stabilized at each toque level. Meaning that if you have 6 bolts to "Q" then you keep tightening each bolt in the proper sequence until none of them move. This allows the item to be properly seated. Which in the case of the head, is extremely critical.

Not that that has to do with setting a peak torque and then turning each bolt another 45-90 degree's. Its just somthing I do as a mechanic. Personally, I don't use the angle torque method to seat anything, I find it far to inaccurate. I simply increase the final torque by 30 in lbs or so and use the seating procedure I just explained.

However, do as you will. What I do is on my car, not yours.

Brian

[Deadeye 5.1]

So is there an actuall final torque setting that one should use? I mean, 90 degrees isn't bad, but with todays torque wrenches I would think that a pre-strech and loosen followed by a specific torque setting would be more acurate than just "90 degrees"

[deezlins]

here is an article on it (also called torque to yield)

http://www.autosite.com/garage...g.asp