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Stretching Connecting Rod Bolts

Practical Engine Building

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I'm currently building a K-series engine and i'm currently stuck in this situation about connecting rod bolt stretching. I'll be reusing my ARP 2000 # 42350 rod bolts that came with my MANLEY H beams.

I have measured all my Rod bolts and paired them to the closest specs using my ARP stretch gauge and noticed one pair had a higher measurement than the rest

A Bolt was measured at free state 42.5

B Bolt was measured at free state 45

Per Manley instructions Cleaned threads, add 30 weight oil on threads and initially torque fastener to 60Ft Lbs(55-65ft lbs)

Bolt stretch limits .0058-.0062

Bolt A installed and measured at .0080

Bolt B installed and measured at .0040

Attached Files

Measuring the stretch of the bolts is a superior technique than relying on the accuracy of your torque wrench. If you exceed the bolt stretch limits, then the bolt has been over torqued and if the bolt is below the spec given, then the bolt needs further tightening to be brought into spec. The guage must also be brought to zero for each bolt you torque.


Thanks for the reply! I figured everything out and everything is now in spec. I ended up using a different calibrated torque wrench, also re cleaned the threads, re added oil on the threads and head and everything came out fine the one that was below the stretch value.

Great to hear! I would love to see a video of it running. Best of luck with the rest of your build.

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