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  #1  
Old 07-09-2011, 09:06 AM
npk npk is offline
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How to re-tighten M111 cylinder head bolts?

Like to know how to re-tighten the head bolts.

The specs says 55NM + 90deg + 90deg (in a specific sequence starting from center)

Do I loosen a bolt, tighten to 50NM(41lbft), move to the next(according to the sequence) till I completed all the bolts , +90Deg to every bolt(according to the sequence again) and +90 Deg according to the seq?

Read that some just add another 1/4 Turn to every bolt (following the sequence).


Some say that torque to 82lb ft.

Which is correct way?

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  #2  
Old 07-09-2011, 01:25 PM
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55nm, start to finish, wait, 1st 90, start to finish, wait, 2nd 90, start to finish. done. good luck, chuck.
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Old 07-09-2011, 06:53 PM
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Originally Posted by porkface View Post
55nm, start to finish, wait, 1st 90, start to finish, wait, 2nd 90, start to finish. done. good luck, chuck.

Does this mean that I have to loosen all the bolts before starting this (55nm, +90, +90)procedure?


But wouldn't loosen all the bolts(nothing to hold the head down to the block) may shift the head and cause the gasket (which has already set-in for several years) to tear/break?
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Old 07-09-2011, 07:14 PM
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Why are you retightening? I don't think that is standard practice, AFAIK.
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  #5  
Old 07-10-2011, 11:37 AM
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This is an old engine left idled for a long period.

Want to ensure that the head is properly fastened before I drop it into the car.

I know that it's not a common practice.

NPK
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  #6  
Old 07-10-2011, 12:13 PM
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i wouldn't touch the head bolts if it's still assembled. what i mentioned is for a head that's been off and a new head gasket. never seen a retorque on an old, broken in gasket. good luck, chuck.
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Old 07-10-2011, 01:16 PM
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Ive retorque a couple of head gaskets on a 104 engine, with good enough
results , probably due to non original gasket installed, my engine was leaking a lot and i didnt want to do the headgasket yet , it significantly
slowed my leak,i did loosen 1 bolt all the way at a time ,then torque acordingly with the2x90 degrees final, cant hurt anything , worth a try

Last edited by nulu; 07-10-2011 at 01:26 PM.
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  #8  
Old 07-10-2011, 02:34 PM
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For any retorque of the head bolts, I'd first check the bolt length to make sure they haven't gone beyond the limit.
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Old 07-10-2011, 02:56 PM
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npk, retightening head bolts on an engine with an old compressed head gasket using the 55nm, +90, +90 method is likely to cause problems such as stripping the threads in the head. I would talk to an indie, a tech at your local MB dealer, or possibly an engine rebuilder before proceeding with any head bolt retightening.
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  #10  
Old 07-10-2011, 08:54 PM
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That would really be an ignorant move to mess with those head bolts that have been down and stressed for a long time. If you think someone has messed with some or all of the headbolts, you only have one course of action and that would be to remove the head and install a new head gasket from scratch and measure all head bolts for stretch and replace as needed.
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Old 07-13-2011, 12:42 PM
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I would leave it alone. The M111 is a masterpiece of engineering. If you really need to do something to feel better then start with the bolts tightened as is and try to torque to 75 or 80 ft lb. If they don't budge then call it good. I am guessing they won't budge. But I would leave it alone unless you have some good reason why you think they might be loose.
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  #12  
Old 07-13-2011, 06:37 PM
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Quote:
Originally Posted by mpolli View Post
I would leave it alone. The M111 is a masterpiece of engineering. If you really need to do something to feel better then start with the bolts tightened as is and try to torque to 75 or 80 ft lb. If they don't budge then call it good. I am guessing they won't budge. But I would leave it alone unless you have some good reason why you think they might be loose.

Thanks...think 75 to 80 ft lbs seem to fair figure to work on to ensure that bolts are tight.

TQ
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Old 07-14-2011, 01:30 AM
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When I did my head gasket (m104), I cranked the Headbolts to 50nm in order and I could not see going any further as when we tried I thought I would snap them off with me and my buddy pulling on the bar (that's what it felt like it would take). But maybe we should have because 1200 miles later, I lost all compression. How do you know if you won't strip or snap these bad boys off when it feels like you can't go any further and thet is with a new head gasget installed?
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Old 07-14-2011, 01:42 PM
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You need to measure the length of the bolts before you start because they have a certain amount of stretch built in but it can get "used up". That is my understanding anyway...

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