I ordered main studs from ARP for my SBO engine rebuild. I'm very confused about the correct torque spec for the main caps; lots of conflicting info. The CSM lists 80 ft-lb for caps #1-4 (which use a 7/16" bolt) and 120 ft-lb for #5 (which uses a 1/2" bolt). For the 7/16" fastener, the ARP website says 80 ft-lbs, with the moly lube, but the ARP box they came in says 63 ft-lbs, and to further add to the confusion, the instructions that came inside the box say 70 ft-lbs. What gives here? I'm planning to assemble the motor myself and don't want to screw up my new engine because I got the torque specs wrong.

Website Info.


Back of the box.


Installation Instructions.

 

I would tend to go with ARP with lube. The #'s aren't that far apart. I think the real important part is to torque them all the same.

 

Did you have your block align honed? In other words did you read the footnote(s)?

Its important.

 

Don:
The machine work on the block will be started next week and align honing the mains is part of the plan. Thanks for the comment.

 

I would give the tech support people a call for clarification. If you need to do it this weekend, I would torque it to the lower numbers of the charts. Leave it alone for a while, then re-torque it to the lower numbers (you will get relaxation due to many factors) USE the ARP Moly lubricant... It helps to improve accuracy of the preload. (reduces scatter in the results) Do you have a non-snap/click torque wrench you can use? (I used to have to throw away the snap/click type wrenches because they would be out of calibration...) Good luck with your project!


After talking to tech support, I would re-torque to the recommended value. The multiple torque sequences help to stabilize the preload, and minimize relaxation of the bolted joint.

 

SO, I sent an email to ARP to find out what torque value was correct, they asked me to check the date on the box. It turns out that I purchased some older stock (the date on my stud kit was 7/27/2006) and ARP has since changed their moly lube formulation which requires a lower torque setting. Another thing I learned from talking with ARP is the main stud kit should have 2 pieces of paper inside; one sheet is for 7/16" studs and the other sheet is for the 1/2" studs for the rear main. The kit I received only had the sheet with instruction for the 7/16" studs. If I had followed their directions, I would have used the wrong torque setting for the larger rear main. I sure am glad I asked questions about this. Thanks to Kitfoxdave for suggesting I contact ARP - that was a good call!