Camshaft Bearings Explained
In its most basic form, bearings are meant to reduce friction—that's what they do for your camshaft. They keep it rotating where it should be and help prevent problematic friction from wreaking havoc on your engine.
In Your Engine
The camshaft bearings are an often overlooked part of the engine. Engine Professional magazine published an article on types of camshaft bearings in their 2015 January-March issue. In it, they mention that because camshaft bearings tend to have fewer issues than crankshaft bearings, they are often overlooked as new advances are made. This hasn't completely stopped innovation, though, as the article goes on to talk about.
As mentioned, the camshaft bearings support the camshaft in the engine and allow for its rotation. Typically, an engine has between 1 and 7 bearings per camshaft, but it depends on your engine type. Engine Professional lists three main configurations of camshafts: overhead valve design, overhead camshaft design with rocker arms, and overhead camshaft design with direct cam operation. This configuration affects the bearing position and load.
For a long time, most camshaft bearings were made of babbitt, a lead-based material that is quite soft and slippery. It is used much less frequently, though, as modern engines tend to operate at much higher temperatures, at which babbitt doesn't perform well, leading to premature fatigue. Instead, bearings are now often made of an aluminum alloy that is much stronger. It has some trade-offs, though, as the alloy is much less forgiving than babbitt and needs to be monitored more closely.
Dirt and other debris can be even more detrimental to an alloy bearing than to a babbitt one, so it's important to make sure the bearings are clean when they are installed. Clearance and alignment are both important when installing bearings to help prevent premature wear and to allow for the proper amount of oil to flow into the clearance space. This lubrication helps reduce friction and keeps your camshaft rotating properly. Be sure to read our earlier blog post, How to Install a Diesel Engine Camshaft, to learn more about camshaft installation.
Causes of Issues in Your Camshaft Bearings
As you can see, camshaft bearings are vital to the proper function of your camshaft. Below are some things that might cause problems for your bearings:
Uneven Bearing Support
It's important that each bearing is installed in its proper position (there is variation in the size of the bearings depending on its intended install position). If the bearings are placed incorrectly, there can be too much clearance. This allows the camshaft to flex, distorting it. This distortion doesn't allow for proper support or lubrication, leading to wear on your bearings.
Improperly Installed Bearings
If a bearing is improperly installed, there can be a lack of lubrication, causing bearing failure. Improper install can result in oil holes being partially or completely covered. This prevents the proper amount of oil from lubricating the camshaft, leading to excessive wear on the bearing. Ensure that the bearings are properly aligned on install to help prevent this issue.
There are several factors that can lead to excessive wear, including improper install, incorrect bearing sizes, or higher operating temperatures. This causes too little lubrication, which leads to wear on the bearings. This wear only makes the lubrication problem worse, leading to eventual bearing failure.
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