Guest Blogger: Street rod 101
Here is some information about crankshaft, connecting rod, and camshaft bearings that may be helpful when working on your street rod engine. There is a lot more to these bearings than meets the eye. These types of bearings are often called “insert” bearings. They are designed as a two piece bearing on the crankshaft and a one piece bearing on the camshafts. They are also referred to as “friction type bearings.” The bearings have a steel backing for strength and support. There are also several soft metals on the bearing surface. Soft metals such as copper-lead (also called Babbitt), aluminum, and tin allow for very small dirt particles to become embedded in the soft metal. They also help the bearing to form closely to the shape of the crankshaft
These bearings are designed to do several things. They must have:
1. Load-carrying capacity—this is the ability of the bearing to withstand pressure
loads, especially from combustion pressures pushing down on the piston and
thus the bearing.
2. Fatigue resistance—this is the ability of the bearing to withstand constant
bending and movement while the engine is running.
3. Embedability—this is the ability of the bearing to permit small foreign
particles in the oil to be embedded or be absorbed into the metal.
4. Conformability—this is the ability of the bearing to be shaped to the
small variations in the shape of the crankshaft or camshaft journal.
5. Corrosion resistance—this is the ability of the bearing to resist the by-products
of combustion that are in the oil and carried to the bearing during operation.
6. Good wear characteristics—this is the ability of the bearing to be strong
enough to eliminate excessive wear, yet soft enough to not the
wear or damagethe crankshaft and camshaft journal surfaces.
7. Thurst absorption--This is the ability to absorb axial thrust on the crankshaft and
camshaft. Axial thrust comes from the use of helical gears.
Crankshaft (main and connecting rod) bearings also have a small locating lug to keep them from spinning. Camshaft bearings use a press fit to keep them from spinning. Oil grooves and holes are also machined into the bearings to allow for sufficient oil lubrication.