XU4J9 head bolt torque

T

ThanosK

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Fellow Frogger
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We are rebuilding a series 1 405 Mi16 engine and the manual calls for torquing the head bolts to 2 kg.m, then angle torquing 300 degrees. At 190 degrees it is already up to 9 kg.m and we hesitate to go higher because of the aluminum block. Does anyone have experience with that?
 
The bolts should be torque to yield. A lot of people strip the thread in the block when they rebuild the engines and then helicoil the block. I did it and I didn't strip any threads. Make sure you clean the threads to perfection, lubricate the threads and the washers under the bolt head. Also, do not use a click type torque wrench. I use one of these :

cscforce.com

Tohnichi Dial Indicating Torque Wrench DB/DBE/DBR Series - C.S.C. Force Measurement, Inc.

Tohnichi DB / DBE / DBR Dial Indicating Torque Wrench Capacities: Nm 0.2-1.5 / 0.3-3 / 0.6-6 / 1-12 / 3-25 / 5-50 / 10-100 / 2-200 / 30-280 / 40-420 / 50-560 / 70-700 / 100-850 / 100-1000 / 200-1400 / 200-2100 / 300-2800 / 500-4500 / 600-6000 kgf.cm 2-15 / 3-30 / 6-60 / 10-120 / 30-250...
cscforce.com cscforce.com
 
Always use new bolts. Once you get to a certain torque it won't increase, as the bolt stretches. A used bolt will not stretch correctly or at all and angle tightening could strip the threads in the block, or the bolt could break. I always just use torque tightening, take it up to the point where the bolts start to stretch, around 65 lbs, never had a problem. 205 GTi Rally Club in the UK recommended 55 lbs.
 
300 deg is correct. I have done it many times. I have also had fails occasionally, and had to helicoil.

Rather than using head bolts, consider studs. I’ve just installed a set from Pug1off. They feel beautiful and torque to 120Nm. The best part is they’re reusable.
 
Thank you, Graham and Peter. Damn, I can't believe I didn't think of the studs! Too late now, I will do it for the next engine. Pug1off has nice things, I got the baffles and Satchshift they sell.
 
Now to make it more complicated
One of many many debates but a goodie
mechanicinsider.com

Head Bolts Vs. Studs – You Need to know!

Deciding between cylinder head bolts vs. studs is a regular debate for mechanics. It depends critically on the functionality of the vehicle. Although bolts
mechanicinsider.com mechanicinsider.com
 
The stud upgrade seems a very good idea. I usually replace every bolt that threads into aluminium with studs if I can simply because sooner or later bolts end up stripping the casting threads (especially fine pitch and especially ones that get taken out a lot for normal operations/maintenance). Just a pain in the butt. Never done it on heads but next build I will look at it. One issue I can see already with my engine (205GTI) is the bolt head is shrouded at the back of the block. Even a torx socket touches the head casting unless it is the long type. Not sure how a normal socket would clear but I'll burn that bridge when I get to it.
 
If the clicker is very sensitive, and W & B tools are, the deflection of the bar is an accurate measure of the bending moment applied within the torque range of the tool.
 
FYI.
 

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Berridale said:
Why/your reason,please?
Click to expand...

This was a longer discussion here some time ago. It started with the Renault 807 engines (of which I had a few at the time). The general consensus was that their accuracy was not good enough for torqueing headbolts in Aluminium blocks because of the way they signal reaching the set torque.
 
Correct. Turbo diesel crank, aftermarket turbo Mi16 rods & pistons, 8V head, Mi16 block.
 
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