How to Inspect the Bending and Twisting Deformation of Connecting Rods?
3 Answers
Before inspection, clean the expandable positioning mandrel of the connecting rod tester, the inspection plate, and the large and small end holes of the connecting rod to be inspected. Place the large end hole of the connecting rod to be inspected over the expandable positioning mandrel, position the connecting rod vertically, expand the mandrel, and secure the connecting rod on the positioning mandrel. Insert an inspection mandrel into the small end hole of the connecting rod, bring the V-groove of the 'three-point gauge' with V-blocks into contact with the inspection mandrel, and ensure the measuring points touch the inspection plate. Use a feeler gauge to measure the gap between the measuring points and the inspection plate to determine and inspect the bending and twisting deformation of the connecting rod.
I've been repairing engines for ten years, and inspecting connecting rod deformation is an essential step in engine overhaul. After removing the connecting rod, support it on a V-block platform and rotate it to check for any sticking, which indicates bending. Torsional deformation is more troublesome - you need to align the small end and big end on two support points of the V-block, then measure distance variation with a micrometer. If it exceeds 0.1mm, it means torsion has occurred. I always emphasize this step cannot be skipped, otherwise reinstalling the rod may cause piston-to-valve contact, accelerated wear, or even engine seizure, doubling repair costs. Basic tools like straight edges can do preliminary screening, but professional calipers are ultimately required for precision. Connecting rod deformation often results from overheating or overloading, and regular inspections can prevent major failures and extend engine life.
As a car modification enthusiast, I use a simple method at home to check connecting rod deformation. Place the rod on a thick glass or smooth flat surface as a reference, press it down firmly and check for any wobbling gaps to detect bending. For twist, measure diagonal distances with a string – if the difference increases, it indicates a problem. When I DIYed my engine swap, I didn't check properly, and the deformed connecting rod caused excessive body vibration, nearly damaging the transmission. I suggest fellow car owners regularly perform visual checks with a ruler or invest in cheap V-blocks as aids. While not as precise as professional equipment, it's sufficient to spot obvious deformations, prevent engine failures, and save on repair costs.
