I hope the answer is not too similar to this question.
I have a basic understanding of the role a crankshaft plays in the internal combustion engine, which leads me to ask:
Image Source: https://en.wikipedia.org/wiki/Crankshaft
The two primary bearing types found on a crankshaft are roller bearings and plain bearings located on the main journals of a crankshaft.
There are two types of journals on a crankshaft.
Main Journal - Where the crankshaft main bearings would be located
Rod/Offset Journal - Where the connecting rod bearings would be located
Crankshaft Components Image
Roller Bearings are frequently pressed onto the crankshaft during assembly. In order to replace bearings that are fitted in this fashion the crank pin/journal needs to be pressed out of the counterweight.
Plain Bearings split in half and are typically associated with crankcases that can split or support main bearing caps. This also true of connecting rods on offset/rod journals. Plain bearings wrap around the journal and are pressurized with oil, the crank journal 'rides' on this layer of oil between the crank journal and the plain bearing. This is called hydrodynamic lubrication.
Camshaft End Bearings are Different
They do not require the load that a crankshaft endures during the combustion process and don't participate in the transfer of power from the combustion process, other than sapping it just a bit.
There are many different designs of cramshaft end bearings. There may be a cap with a roller bearing or a needle bearing in it, as in the image below or simply a cap over a camshaft main journal.
A camshaft end bearing is also designed to reduce lateral movement of the camshaft in order for it to stay within a given lateral tolerance so the cam lobes always ride on the correct valve bucket or rocker arm.
The image below shows the use of camshaft end cap bearings in use.
