Rod bolt nut torque

[porschedavid]

1984 Porsche 911 3.2 carrera
Doing engine rebuild, what torque do you do the ribbed nuts for rod bolts

[Flat6pac]

15# 90 degree swing
Bruce

[porschedavid]

is that 15 Nm, and for the rib nuts

[KTL]

15 Nm + 90° is the cylinder head/head stud nuts. The connecting rods are 20 Nm + 90°

The image below is a scan of the '84-'87 spec book

[proffighter]

Maybe you make the same mistake like many others, even pros. Rod bolts have changed since a while and so you should know this (guess no one uses still 30+ years old bolts)

[porschedavid]

Is the torque 20nm + 90 for the ribbed nuts, not the hexagon nuts

[KTL]

Thanks for adding that Roland. As soon as I saw your tech bulletin with the 00 vs. 12.9 bolts, I remembered seeing that before. I'll save that in my collection of tech info so I don't forget next time.

Out of curiosity I looked in the Bentley 964 technical reference companion book and it was nice to see this tech info was included there as well.

Kev

[KTL]

Originally Posted by porschedavid

Is the torque 20nm + 90 for the ribbed nuts, not the hexagon nuts

Not sure what ribbed nuts you're referring to. The typical OEM rod bolt nuts are plain style hex nuts with no flange, no ribbed surface. I don't think ribbed nuts are specified on connecting rods because the ribs are intended to dig into the material to lock the nut. That disturbance of the metal in the surface of the rod and that creates stress risers on a component that is rather sensitive to stress?



That being said, I do recognize that the bolt bore in the big end of the rod is a relatively low stress area compared to the rest of the rod. Still, I don't think a nut digging into the rod material is a good thing.

[Quicksilver]

Originally Posted by Flat6pac

15# 90 degree swing
Bruce

Flat6pac was correct for the "00" bolts. He used a pound symbol - "#".

20 Nm = 14.75 foot/pounds so I think a 0.25 ft/lb over torque is ok.