Rod bolt stretch

[bentvalves]

"I recently talked to a scat tech at the 1 800 help line about this concern. The tech guy said that they were advising torque method only because of the excessive stress and distortion placed on the rod material. Lube torque and loosen and retorque. He said that possibly the necessary 90-100 lb torque required to achieve the bolt stretch is too much for the rod. for a 500 is HP engine I no longer have any concern If the application is a more extreme build I will use the bolt stretch method and resize the rod after the stretch torque before final assembly"

[FC-Pilot]

Back with the old arp lube they recommended that you torque and loosen the bolt or nut something like five times before final assembly. I would measure stretch at each torque and just as described the threads would burnish and by the last torquing the stretch would be right at the recommended numbers. After having a bolt come lose and losing an engine due to inadequate stretch (as I only torqued them once on assembly and did not check stretch) I always torque them in a vice and check the stretch. Also, if by using torque and then the measured stretch is too high that would show a bad bolt. I have not seen that, but is just another thing that can be verified during the build.

Paul

[David Redszus]

Tightening torque (with a torque wrench) only refers to the frictional force of threads, bolt head, and washer. It does not
measure anything else.

Depending on thread cutting method (cut, rolled or ground), the friction factor can range significantly (0.08 to 0.22). Tightening the bolt in several steps, allows the surfaces to become burnished and smoothed, which will change the frictional force required.
The same is true for oiled vs dry threads. And plated threads.

Bolt stretch length is the most accurate method of tightening bolt. Many OEMs will specify the bolt length and/or diameter limits of a bolt to determine whether a bolt may be reused or not. Thread distortion can be determined by running a nut along the threaded length while observing binding.

[digger]

Tightening torque (with a torque wrench) only refers to the frictional force of threads, bolt head, and washer. It does not
measure anything else.

Depending on thread cutting method (cut, rolled or ground), the friction factor can range significantly (0.08 to 0.22). Tightening the bolt in several steps, allows the surfaces to become burnished and smoothed, which will change the frictional force required.
The same is true for oiled vs dry threads. And plated threads.

Bolt stretch length is the most accurate method of tightening bolt. Many OEMs will specify the bolt length and/or diameter limits of a bolt to determine whether a bolt may be reused or not. Thread distortion can be determined by running a nut along the threaded length while observing binding.

With quality parts and following the recommended procedure by the manufacturer a torque wrench works plenty fine

[midnightbluS10]

Sorry, but the way he is intending to do it without the proper tools IS playing with Fire!

Asking a question ≠ intentions to do it.

Where'd you get that idea? He's got the proper tools. Seems to me he was just asking a question. <shrug>