Connecting Rod Bearing Size Chart: A Comprehensive Guide for Engine Builders
Connecting rods are crucial components in internal combustion engines, responsible for transmitting forces between the piston and the crankshaft. The connecting rod bearings, also known as connecting rod bushings or rod bearings, are precision-engineered components that allow the connecting rod to rotate smoothly on the crankshaft journal. The correct size of the connecting rod bearing is essential for proper engine operation and longevity. This article provides a comprehensive connecting rod bearing size chart and guidance to help you select the correct bearing for your specific engine application.
Connecting Rod Bearing Size Chart
The connecting rod bearing size chart below provides the dimensions of common connecting rod bearings used in various engines. The chart includes the bore diameter, width, and thickness of the bearing, as well as the corresponding crankshaft journal diameter.
| Bore Diameter (mm) |
Width (mm) |
Thickness (mm) |
Crankshaft Journal Diameter (mm) |
| 45.00 |
19.00 |
19.00 |
44.98 |
| 47.96 |
19.00 |
19.00 |
47.94 |
| 48.00 |
19.00 |
19.00 |
47.98 |
| 50.00 |
19.00 |
19.00 |
49.98 |
| 52.00 |
19.00 |
19.00 |
51.98 |
| 53.00 |
19.00 |
19.00 |
52.98 |
| 55.00 |
22.00 |
19.00 |
54.98 |
| 56.00 |
22.00 |
19.00 |
55.98 |
| 57.00 |
22.00 |
19.00 |
56.98 |
| 58.00 |
22.00 |
19.00 |
57.98 |
| 59.00 |
22.00 |
19.00 |
58.98 |
| 60.00 |
22.00 |
19.00 |
59.98 |
| 62.00 |
22.00 |
19.00 |
61.98 |
| 63.00 |
22.00 |
19.00 |
62.98 |
| 64.00 |
22.00 |
19.00 |
63.98 |
| 65.00 |
22.00 |
19.00 |
64.98 |
| 66.00 |
22.00 |
19.00 |
65.98 |
| 67.00 |
22.00 |
19.00 |
66.98 |
| 68.00 |
22.00 |
19.00 |
67.98 |
| 69.00 |
22.00 |
19.00 |
68.98 |
| 70.00 |
22.00 |
19.00 |
69.98 |
Factors to Consider When Selecting Connecting Rod Bearings
In addition to the dimensions provided in the chart, there are several other factors to consider when selecting connecting rod bearings:
Material: Connecting rod bearings are typically made of steel, bronze, or aluminum alloys. Different materials offer varying levels of strength, durability, and wear resistance.
Oil Clearance: The oil clearance between the bearing and the crankshaft journal is critical for proper lubrication. Too much clearance can lead to bearing failure, while too little clearance can cause excessive wear.
Surface Finish: The surface finish of the bearing should be smooth and free of imperfections. A rough surface finish can increase friction and wear.
Load Capacity: The load capacity of the bearing refers to the maximum load it can withstand without failing. The load capacity should be sufficient for the specific engine application.
Tips for Installing Connecting Rod Bearings
When installing connecting rod bearings, it is important to follow the manufacturer's instructions carefully. Here are a few general tips to ensure a successful installation:
- Clean all mating surfaces thoroughly with a degreaser.
- Apply a thin layer of assembly lube to the bearing surface.
- Carefully position the bearing in the connecting rod and the crankshaft journal.
- Torque the bearing cap bolts to the specified torque using a torque wrench.
Troubleshooting Connecting Rod Bearing Issues
Connecting rod bearing issues can often be identified by symptoms such as knocking noises, decreased engine performance, and increased oil consumption. If you suspect that you have a connecting rod bearing problem, it is important to seek professional diagnosis and repair as soon as possible. Ignoring a connecting rod bearing problem can lead to serious engine damage.
Interesting Stories
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In the early days of automotive racing, connecting rod bearing failures were common. One story tells of a driver who was disqualified from a race after his engine blew up on the last lap. Upon inspection, it was found that the connecting rod bearings had been installed upside down.
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Another story involves a mechanic who was working on a customer's engine. The mechanic accidentally dropped one of the connecting rod bearing shells into the oil pan. He fished it out, and without thinking, wiped it off on his greasy overalls. He then proceeded to install the bearing, only to find out later that the engine would not start. The reason? The bearing was coated in grease, which prevented the oil from reaching the bearing surface.
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A third story involves a drag racer who was having trouble with his engine. He suspected that the connecting rod bearings were worn out, so he decided to replace them. He went to the auto parts store and bought a set of new bearings. However, when he went to install the bearings, he discovered that they were the wrong size. He had accidentally bought bearings for a different engine model.
What We Learn: These stories illustrate the importance of using the correct connecting rod bearings for your specific engine application. They also highlight the importance of following the manufacturer's instructions for installation and maintenance.
Conclusion
The connecting rod bearing is a critical component in an internal combustion engine. The correct size and type of bearing is essential for proper engine operation and longevity. By following the guidance provided in this article, you can select the correct connecting rod bearings for your specific engine application.
