Head bolt shearing off when tightening

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Dweezil
C 111
Posts: 952
Joined: Wed 04 Jul, 2007 11:34 pm
Model you own: w123
Region: New South Wales
Location: Lovely downtown Katoomba

Head bolt shearing off when tightening

Post by Dweezil » Sun 03 Jun, 2018 3:15 pm

Hi Team,

so, I finally got the bits and pieces I need to put the OM617 head on.

Using what I consider to be a normal torque wrench I'm tightening down the first bolt using the 40NM / 30ftlb setting and I'm pulling pretty hard, waiting for the 'click' on the wrench. The only click was the bolt snapping.

I lifted the head and was able to just unscrew the remainder of the bolt from the block quite easily.

So a few questions:

Can torque wrenches just not click 'stop'?

How much force, anecdotally, is the 70NM + 180deg? Firm or gorilla?

Original bolts were within spec, so I reused them. Does anyone in Oz sell them these days?

I also discovered a bit of piston slap on #3 and #4 - I'm guessing about .8mm and .4mm. That will obviously give unequal compression figures, but any port in a storm at this stage. Am I wasting my time there?

Thanks

Dweezil

Dweezil
C 111
Posts: 952
Joined: Wed 04 Jul, 2007 11:34 pm
Model you own: w123
Region: New South Wales
Location: Lovely downtown Katoomba

Re: Head bolt shearing off when tightening

Post by Dweezil » Sun 03 Jun, 2018 5:09 pm

Ok, a little update.

I had the bright idea of using an old OM617 that was lying around to practice on. Turns out that 40NM isn't actually that much at all.

Still no idea why the torque wrench let me go crazy. :dontknow:

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Bartman4800
300 SLR
Posts: 1942
Joined: Fri 10 Oct, 2008 12:10 am
Model you own: w111
Location: Perth WA

Re: Head bolt shearing off when tightening

Post by Bartman4800 » Wed 06 Jun, 2018 4:36 pm

.8 mm and even .4 mm of piston slap is an awful lot.

If it is wear in the bore you won't get decent compression and you need a full rebore, pistons, rings and whatnot

If it is wear in the pistons, you might still get decent compression but when you load up the engine at low revs you can hear the pistons slap...

I think you are wasting your time here, if you want to drive this a bit longer....



Bart
1963 220 Sb Sedan "Kermit" (Australian Assembly)
1960 220 Sb Sedan "Zum Schlachten" (Early German Assembly, with a torsion bar spring for the bonnet) - Stored in Country WA
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