460 head bolt tightening advice required

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Sun, 13/07/2008 - 06:27
w4hsa
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Location: Rutland

Hi, putting cylinder head back on yesterday and rain stopped play just as about to torque down head...

On checking my 460 book head bolts (12point) should be done in three stages 70newton/ metre (am assuming nm as it didn't give ft/lb or n/m?) then settle for 10mins, stage 2 = 90 degree deflection, stage 3 =90 degree deflection?

How does this 90 degree deflection work?...tighten bolt to 70n/m then take torque wrench another 90 degrees for stage2 and then repeat for stage 3? So therefore 180 in total.

Why not the standard 3 torque settings type of thing I'm used to??
:confuzed:

Andy

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Sun, 13/07/2008 - 07:21
#1
Roly
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Re: 460 head bolt tightening advice required

The manual says to torque first stage to 70nm. Starting bolt 2 and doing diagonals only.
Second stage is 110nm to all bolts again in a set sequence moving out from centre.
I'll try to scan the page but the scanner is not working on the new computer so I have to fix that first.

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Wed, 16/07/2008 - 08:42
#2
Arnie
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Re: 460 head bolt tightening advice required

The 90 degree torquing stages are probably more accurate, since what you are trying to achieve is a pre-determined level of tension on each bolt and with torque-wrench settings at higher torques this depends very much on friction, oil on the bolts etc.

The initial torquing at 70NM is designed to insure uniform contact or the head, gasket and block. Then, from this point of contact, tension is applied through a rotation of 2 x 90 deg.

If that was specified in the MB manual, I'd go with that, rather than the 110NM

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