Hi all been outside over the weekend fitting new rod bolts to my 156mm oiliver extreme rods, I got myself a stretch gauge to install them correctly.

The install of the bolts went well and all bolts are sitting in between 5 and 5.4 thou of stretch which is the spec Oliver supply with the bolts.

The bolts got to there correct stretch between 40ftlb and 43ftlb, I know the actuall torque figure has nothing to do with the stretch of the bolts it all depends on the friction between the bolts and rod cap right??

I'm just trying to get it out of my head that the torque figure has no relation to at hat point the bolts gets to its correct stretch.

Thanks

Craig

 

Well, there is a definite relationship between torque and stretch - more torque means more stretch. But, as you state, that is not always linear according to associated friction. All torque specs also i include what type, if any, lube is involved.

Bolt stretch measurement is the most accurate method for setting threaded fastener loads. Unfortunately it's not available for all the bolts.

 

The lube used was the stuff supplied by oliver with the bolts, i read somewhere on the internet about some differences with some ARP lube that made some rod bolts come into the stretch limit 20ft/lb over what the install instructions said it should be.

The instructions i have dont give a final torque figure at all they say to set the bolts to 25ft/lb then add 42degrees of stretch and if the bolt falls short of the desired stretch add 2 degrees to the stretch and do it again.

 

^
That's correct. If the stretch is correct, the applied torque is irrelevant.