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The crack cap of the stock rods. During the production process this method is cost-effective and easy to do: GM bores out the center to the correct outer diameter, then a groove is machined at the center of the two halves to act as a stress riser. That riser makes the rod break perfectly in half in a later step. This method is good enough for a factory application, but because there is a permanent crack, there is no way to resize the big end of the rod in a performance application. Machining is always needed in a normal small-block GM to verify that they are perfectly round and to get the proper crush on the bearing.