Q On Main And Rod Caps Torque Specs
Q On Main And Rod Caps Torque Specs The specs for the main caps in an LS2 call for 15 lb/ft for all, then 80* on the bolts and 51* on the studs. Can someone please explain why the wide disparity, considering they are both M10?
Also, the rod bolts ('10 LY6 rods and pistons) call for 15lb/ft then 85*. Seems odd that the rod bolts would have a higher torque spec. Plastigaging the rods showed the clearance to be in spec, but after running the engine for a while, the bearing wear showed the clearance to be tighter at the splits and wondered if the torque spec had anything to do with it.
Thanks,
Also, the rod bolts ('10 LY6 rods and pistons) call for 15lb/ft then 85*. Seems odd that the rod bolts would have a higher torque spec. Plastigaging the rods showed the clearance to be in spec, but after running the engine for a while, the bearing wear showed the clearance to be tighter at the splits and wondered if the torque spec had anything to do with it.
Thanks,
The specs for the main caps in an LS2 call for 15 lb/ft for all, then 80* on the bolts and 51* on the studs. Can someone please explain why the wide disparity, considering they are both M10?
Also, the rod bolts ('10 LY6 rods and pistons) call for 15lb/ft then 85*. Seems odd that the rod bolts would have a higher torque spec. Plastigaging the rods showed the clearance to be in spec, but after running the engine for a while, the bearing wear showed the clearance to be tighter at the splits and wondered if the torque spec had anything to do with it.
Thanks,
Also, the rod bolts ('10 LY6 rods and pistons) call for 15lb/ft then 85*. Seems odd that the rod bolts would have a higher torque spec. Plastigaging the rods showed the clearance to be in spec, but after running the engine for a while, the bearing wear showed the clearance to be tighter at the splits and wondered if the torque spec had anything to do with it.
Thanks,
As far as the rods, the higher angle doesn't mean higher torque. It's a much smaller fastener so it will actually translate into less torque or force.
Usually the clearance is greater at the parting line of the bearings so there is usually a line where there is no wear in that area. If it's the opposite, something is definitely off.
They tried ARP lube, oil on the threads and even extreme pressure lube but could not get a repeatable measurement until they honed the big ends just a few strokes to put a clean cross hatch in there which grabs the bearing shell but doesn't exceed the bore diameter spec
A.R.,
glad to see someone else chiming in the rod bore distortion. I'll look into doing exactly what you did.
KCS,
don't know enough about how torque angle equates to lb/ft, but it just seems logical that if you are tightening a fastener, the more you tighten it, the more lb/ft of torque is being applied. Could be wrong. As for the mains, ARP studs are 60lb/ft inner and 50lb/ft outer for a 20% difference. Old school 4-bolt main SBC were 70 and 65, less that 10% difference. Maybe torque angle is totally different, but an almost 60% difference in torque angles seems odd. Just wondering why.
glad to see someone else chiming in the rod bore distortion. I'll look into doing exactly what you did.
KCS,
don't know enough about how torque angle equates to lb/ft, but it just seems logical that if you are tightening a fastener, the more you tighten it, the more lb/ft of torque is being applied. Could be wrong. As for the mains, ARP studs are 60lb/ft inner and 50lb/ft outer for a 20% difference. Old school 4-bolt main SBC were 70 and 65, less that 10% difference. Maybe torque angle is totally different, but an almost 60% difference in torque angles seems odd. Just wondering why.
KCS,
don't know enough about how torque angle equates to lb/ft, but it just seems logical that if you are tightening a fastener, the more you tighten it, the more lb/ft of torque is being applied. Could be wrong. As for the mains, ARP studs are 60lb/ft inner and 50lb/ft outer for a 20% difference. Old school 4-bolt main SBC were 70 and 65, less that 10% difference. Maybe torque angle is totally different, but an almost 60% difference in torque angles seems odd. Just wondering why.
don't know enough about how torque angle equates to lb/ft, but it just seems logical that if you are tightening a fastener, the more you tighten it, the more lb/ft of torque is being applied. Could be wrong. As for the mains, ARP studs are 60lb/ft inner and 50lb/ft outer for a 20% difference. Old school 4-bolt main SBC were 70 and 65, less that 10% difference. Maybe torque angle is totally different, but an almost 60% difference in torque angles seems odd. Just wondering why.
The same concept applies to fasteners; they're very much like a spring. Since the main bolts are much thicker, it takes more force to stretch them, which is what's happening when you tighten a fastener.
