torque for arp rod bolts

[edbaus]

Hi,

I have arp rod bolts for my 79 930.

I have no idea what the torquing instructions are. Can someone help me.

Thanks

Ed

[efhughes3]

Torqueing is not the preferred method, measuring bolt stretch is. Do a search, there are many threads on the subject. Also, ARP has full specs on their products on their website. Both torque and stretch, but again, research will show you that torque is an inexact measurement at best, you're really after bolt stretch for proper installation and longevity of your rod bearings.

[304065]

+1 Ed. (the Ed who said, "get a stretch gage."

[cstreit]

Ed (baus) I like stretch as well, but I also use a torque wrench to get it done. IF the bolt has problems (And I've seen 3-4 that have) you'll get the appropriate stretch without getting proper torque levels.
Use a stretch guage, but tighten the bolt with a torque wrench to ensure you get a certain minimum torque on it. I usually set the wrench with 10% less than their suggested torque value. Then I go for the recommended stretch, or suggested torque, whichever is greater.

[chris_seven]

Originally Posted by cstreit

Then I go for the recommended stretch, or suggested torque, whichever is greater.

Surely if you use the greater value based on torque the stretch will be too high and you will have overtightened the bolt.

If the stretch is higher than the torque then it should be quite safe.

I don't think you should mix torque and stretch as it just isn't christian.

The idea of stretch gauges is to remove the uncertainty caused by uneven lubrication from the tightening procedure.

If you look at 'dry' torque figures you can reduce torque by around 20% using a simple oil lube and I believe by 50% by using ARP's new thread lube.

I would be interested to know the bolt problem that reduces torque but increases stretch. The only thing that I can think of is a significantly yielded bolt which is already exhibiting non-uniform elongation. This would be typical behaviour for a 'stretch' bolt that has already been used beyond its maximum recommended length.

I

[ZOA NOM]

You will find that the ARP's will require more than the 35 lbs of torque called for to achieve the .0117 - .012" of stretch. You should, however, perform the process of torquing to 35, back off, again to 35, back off, and again to 35. Check the length, and add torque if necessary. Also, be sure to use the lube that came with the bolts. A simple outside micrometer works just fine.

edit: The values I quoted are for my '87, which has 9mm rod bolts. Your '79 has 10mm bolts, so the values may differ, but the process should be the same.

[chris_seven]

I would tend to agree that new bolts will need higher torque and it has been posted in earlier threads that if you use torque as a measurement then you will need to tighten several times to 'burnish' the threads and reduce stiction.

If you use stretch you don't really have to carry out this procedure.

[RoninLB]

when i installed raceware rod bolts porsche factory torque numbers and raceware numbers weren't even close.

A call to raceware received "Yep, we know that our info doesn't come close to the stretch numbers. Tighten them till they stretch to specs."

[ChrisBennet]

Originally Posted by ZOANAS

You will find that the ARP's will require more than the 35 lbs of torque called for to achieve the .0117 - .012" of stretch. You should, however, perform the process of torquing to 35, back off, again to 35, back off, and again to 35. Check the length, and add torque if necessary. Also, be sure to use the lube that came with the bolts. A simple outside micrometer works just fine.

edit: The values I quoted are for my '87, which has 9mm rod bolts. Your '79 has 10mm bolts, so the values may differ, but the process should be the same.

I can confirm that the stretch method produces a stretch below the recommend stretch for both ARP and Raceware rod bolts.

The 79 Turbo and '87 Carrera both use the same 9mm rod bolts.

-Chris

[edbaus]

I have completed this task and can also agree with the fact that the 35 ft lbs does not meet the required stretch. I was only getting about .007 to .009 at 35.

Thanks

Ed

[hifeverz]

Ed:
. . . sent you a P.M.
thanks,
Hz

[aws]

Ed: Nobody has mentioned that the rods need to be reconditioned with the ARP bolts installed to maintain roundness on the big end. I have had occasion over the years to install rods with ARP bolts when the case was assembled and it is very hard to use a stretch gauge under those circumstances and I have torqued each individual rod bolt to attain the correct stretch on the bench, then installed the rod on the crank. Using this method I have found the median torque to be over 55lbs to attain the correct stretch. ( no matter how many cycles the nut-bolt have been through) I have always unseated the big end cap of the rod after being reconditioned, re-stretched the bolts and rechecked the big end with a dial bore gauge. Even with a correctly reconditioned rod you will get .0001 to .0002 out of round due to the way the cap aligns on the bolt. I believe the factory spec is .0005.

aws

[aws]

Ed: Nobody has mentioned that the rods need to be reconditioned with the ARP bolts installed to maintain roundness on the big end. I have had occasion over the years to install rods with ARP bolts when the case was assembled and it is very hard to use a stretch gauge under those circumstances and I have torqued each individual rod bolt to attain the correct stretch on the bench, then installed the rod on the crank. Using this method I have found the median torque to be over 55lbs to attain the correct stretch. ( no matter how many cycles the nut-bolt have been through) I have always unseated the big end cap of the rod after being reconditioned, re-stretched the bolts and rechecked the big end with a dial bore gauge. Even with a correctly reconditioned rod you will get .0001 to .0002 out of round due to the way the cap aligns on the bolt. I believe the factory spec is .0005.

aws

[RoninLB]

Originally Posted by aws

Nobody has mentioned that the rods need to be reconditioned with the ARP bolts installed to maintain roundness on the big end.

above is news to me...... thx




and my Raceware rod bolts had to be torqued way over factory to attain mfg stretch. I even called Raceware and asked them about it in mid session. He said that's routine and the 2.7 bolts are more of an issue than the smaller diameter 3.2 bolts.

[Jeff Alton]

You think you are going to pull a cap out of round using the ARP bolts???? Really?

Cheers