Rb30 Arp Main Stud Part Numbers And Torque Figure

[mambastu]

Hi All,

I bought some ARP main studs for my RB30/26 about 5 years ago from Spool and recently started building the engine.

The block was sent away for machining with the studs and I requested that the mains girdle be torqued to 65-70 ft lbs with ARP Moly lube for the main tunnel honing as per the torque specs in this thread http://www.skylinesaustralia.com/forums/topic/388491-help-what-tension-arp-main-studs/?hl=arp+main+torque#entry6196886

Got the block back and torqued the girdle down to 70ft lbs to measure the bearing clearances with plastigauge. Clearances were fine so final assembled and then found that I needed to cut one of the 3 long studs down to clear the shaft that passes through the RB26 sump. Released the girdle, cut the appropriate stud down and re-assembled back in its hole. Torqued the main bearing ladder back down and one of the shorter studs sheared before it reached 70 ftlbs !

Managed to drill the bugger out but now I'm left wondering why exactly it sheared. The threads in the block were clean. The stud was hand tightened first. ARP moly lube was used in assembly and the main studs were tightened in the appropriate order with a good quality Snap-on torque wrench.

Is it just a case of 70ftlbs is too much or could it be a faulty stud ?

Should I replace the whole set as a precaution or is it safe to just replace the single stud do you think ? If thats the case does anyone know the ARP part number for one of the short studs ? It would appear to be M10 x1.5 where it screws into the block, 105mm long and the nut end would appear to be a different pitch thread - possibly M10 x 1.25

During my searching I've found torque figures of 55, 60, 65, 70 and 73-75 ft lbs for RB ARP main studs so some clarity and real world experiences would be nice.

Edited June 17, 2013 by mambastu

[Gerg_R31]

All the arp main stud kits I used at work were all 60 or 65ft as stated on the spec sheet they came with

[mambastu]

I'm told by ARP that there isn't an official main stud kit for the RB30 and the stud kit arrived in a bag so Spool must make up a kit and unfortunately there wasn't a spec sheet with them.

Incidentally the 73-75 ft lb torque figure came from your excellent thread at http://www.skylinesaustralia.com/forums/topic/378823-engine-internals-comp-ratios-general-info/?hl=%2Barp+%2Bmain+%2Bstud+%2Btorque if you're able to edit that at all (you may not be able to due to its age) it could help people with future searches.

[Gerg_R31]

wow never noticed that, thanks for pointing that out (i'll look into getting that changed by a mod or something)

but yeah, ARP bolts have always turned up in a box for me with settings that either say 60 or 65

[White GTS-T]

Just to clarify, was the stud that you cut, the one that broke?

[mambastu]

No, I cut one of the long studs down and it was one of the short studs that sheared.

Edited June 20, 2013 by mambastu

[Ben C34]

Considering one has snapped due to over tightening, I would definitely be replacing the rest.

[luke gtr]

Considering one has snapped due to over tightening, I would definitely be replacing the rest.

this.

I thought they were meant to be torqued to factory specs unless stated?

[mambastu]

Considering one has snapped due to over tightening, I would definitely be replacing the rest.

Yes, not worth risking the other studs. I've ordered a new set.

Thanks for your help fellas.

[Gts4RB30]

There has been a batch of arp studs floating around snapping. I usually torque them to factory nm +10nm and NEVER have a issue however a couple of years ago we had several engines primarily rb getting snapped studs on factory or below torque settings. We werent the only people to of suffered this. Try getting arp2000 or l-19 studs. Secondly DO NOT CUT that stud down. Have it machined off at a machine shop. TBH ive NEVER had any clearance issues with this stud so many have

[GTRNUR]

When was your torque wrench last calibrated? Just because its a snap on wrench it doesn't mean its even close to being with spec. They are a pain in the ass to calibrate and get parts for too.

Seriously consider having it calibrated again before you do up another set of studs, lest you start breaking rod bolts next.