ARP Rod bolts - RR rods

[tocobill]

So Im assembling my crank for the final time and torquing my ARP rod bolts on the RR rods I have. I am measuring stretch with a ARP gauge and confirming the torque at the specified stretch. The RR paper work that came with the rods states not to exceed the torque of 47 FT/Lbs and to stretch the bolts to .0055-.0060". I did confirm these stretch numbers with R&R. Some bolts I get .0045-.0050 stretch at 45 ft/lbs and others I get .0055-.0060" at 30-35 ft/lbs. Im at a loss right now and going to call R&R tmrw to see what they think.

Any advise? These rods are very similar to carrillo rods and the bolts are 3/8 ARP 2000 bolts.

[KTL]

What lubricant are you using on the threads? It makes a big difference. By comparison, Pauter makes clear mention of this when stating the torque specs with their rods & ARP bolts

Rod Info - Pauter

When they state a specific torque, they should qualify that with what lubricant they're using. When stretching the bolt, the lubricant is somewhat irrelevant in that you're just trying to reach that specified stretch. However lubricant is important in that it must lube the threads and avoid galling them as you're trying to achieve that specified stretch amount.

[tocobill]

Hey Kevin ... I got the rod torqued from RR with ARP bolt lube on them. I cleaned all the bolt threads and rod cap threads and re applied the ARP lube supplied. RR specs that you should not exceed 47ft/lbs when torquing bolts. Other threads Ive read have guys tightening bolts until the .0055-.0060" is met with Carrillo rods etc. I seem to be getting different torque values for the same amount of stretch ... They should all be in a range? At least that's what I would expect. Then on my last rod tonight I got dont attaching the rod and when torqued the rod binds ... ugggghhhh. The rod journals are all .0015-.0018" when spot checked with plastic gauge. IF I loosen the bolts slightly the rod spins fine.

[KTL]

Good move making sure everything is super clean. New rods shouldn't be an issue with clean but you never know. For instance, when I had my Pauter rods re-done at Pauter, there was honing grit in the bolt areas. Apparently they just torqued the rod & cap to spec, honed & measured for proper bore sizing and called it good. So I learned my lesson when I disassembled the rods and didn't thoroughly clean them upon reassembly.

ARP lube is some super slick stuff, so I certainly understand your concern that you're not reaching specified stretch by the time you hit 47 ft-lbs. I agree that you should be seeing a range of torque values to achieve the desired stretch.

My Pauter bolts are also the 3/8" ARP 2000 and I recall my torque values being like 50-54 ft-lbs to achieve the desired stretch. I was using Permatex Ultra Slick assembly lube (super sticky red liquid goo).

Its been said that its good to "burnish" the bolts to normalize their behavior to torquing. Basically its tightening and loosening the threads to run them together and gets them mating smoothly. So after two or three tighten-loosen cycles, the torque required to stretch the bolts a specified amount should be more consistent than just doing the tightening once with brand new virgin bolts.

I would un-do the suspect rod and see if your bearings are sitting right in the tang grooves? Hard not for them to be sitting in the rod properly because the "squish" that occurs when the cap meets the big end tends to get them lined up. Still, one needs to be particular about getting the bearings nicely seated in the bores.

Herein lies the downside to plastigauge IMO. W/out using a bore gauge you're not able to see what's going on in the rod when it's tightened. With the bore gauge, you can torque the rod cap to spec and then measure the bore to see if its distorted.

[Lapkritis]

Check the stamping on the sticking rod bearing. Ensure you don't have a U.25 in there... saw that just last week on an S50/M50 rebuild. Always test for ease of rotation before moving to the next is a best practice.