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rover_400_95_99
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I thought that the problem with a torque figure is that differing thread friction on each bollt will result in different loading. The rotation method applies a loading dependent on the thread pitch which will be the same for each bolt. Maybe I'm wrong?
 

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'06 MG ZR +120 (HQM) '04 MG ZR 105 (IAB)
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^^^^^That is exactly it :)

......If you want even tightness, why not use a torque wrench? Add stages if you need to build it up slowly.
You can't because it isn't that simple; Due to the lower clamping load that could be achieved because of the flexibility of the bolts and the softer aluminium castings, the tightness of the bolts was critical.

You actually need to tighten beyond yield to get the full clamping load - most engine bolts are tightened straight into yield. Because of the less robust nature of the aluminium alloy, The K series bolts have to tightened to just shy of yield so that the expansion when the engine is hot take them just beyond yield.

There will be slight variations in friction between one bolt and another (due to microscopic differences in the machining of the threads, debris in the threads (which there will be, even if you have tried to clean them) and differences in friction between the head of the bolt and the machined surface of the head against which they tighten. This results in the same torque wrench setting potentially taking each bolt down to a slightly different tightness.

Using a low torque with torque wrench will settle all the bolts to the same point, and using an angle tightening procedure then tightens them all down by exactly the same (known) amount.

Roger Stone explains it more deeply and clearly from 2min 35secs into this clip from an early 1990s Open University programme: K Series Long Bolt Pt2: YouTube

That is part 2; Part 1 is here if you are interested: K Series Long Bolt Pt1: YouTube

And a shorter explanation in a post by 1955diesel on this forum some years ago: What gasket and bolts is this?
 
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