Tuesday, November 26, 2013
How to Connect Rod Journal Measurements
Connecting rods connect the piston to the crankshaft; as the crankshaft rotates, the connecting rods move the piston up and down in time with the rest of the engine. A connecting rod journal is where the connecting rod attaches to the crankshaft, making the journal a crankshaft feature. Measuring connecting rod journals is an important part of an engine rebuild, helping you determine the proper size connecting rod you need. To measure connecting rod journals, the crankshaft must be already removed from the engine.
Instructions
- 1
Locate the connecting rod journals on the crankshaft. The number of connecting rod journals depends on the number of cylinders. A four-cylinder engine has four, and an eight- cylinder has eight. Journals are smooth, polished surfaces, located in between the crankshaft counterweights. Crankshafts also have main journals, allowing them to rotate. Connecting rod journals are the smaller journals.
2Feel the journals with your fingers, and determine if they require machining. Journals should be polished and smooth. If theyre rough, pitted, or rusted, they need to be machined by a professional prior to measuring, as machining changes the journals measurements.
3Use a micrometer to measure the connecting rod journal. Open the micrometer by turning the handle until the journal fits inside. Place the micrometer at the journals center, turning the handle until it closes on the journal.
4Record the measurement given. The measurement is found on the micrometer sleeve, directly in front of the turning handle, or thimble. Connecting rod journals are commonly measured in millimeters.
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