In order to retain the original big end bore, both faces (of the cap and the rod part) need to be machined prior to the drilling operation. This will render a slightly shorter rod. In addition, careful measurement of the second rod is required, and resurfacing cap and rod may deviate from the first rod.When being resized, the faces of the cap are probably ground, then the cap and rod are machined as an assembly.
The small end bore center is the datum for for this operation (assuming straight non-twisted rods). Now, if the big end has become oval, I expect the small end to be oval as well, and this will require the small end to be bushed and drilled off-center in order to restore the correct rod length. The (oversize) bush can be fitted by either enlarging the bore, or by use of an expanding technique using the old bore.
- Knut
Connecting Rod Reconditioning: More to it than you might think - Engine Builder Magazine
The connecting rod plays a vital role in the engine. But a connecting rod is under tremendous stress, with the weight of the piston sitting on top, changing direction thousands of times per minute. This continuous stopping and changing of direction combined with the weight of the piston and...
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