Preventing Premature Cam Bearing Failure
Have you thought much about the material your camshaft bearings are made of?
Odds are, this isn't something you've put a lot of thought into. But, the material of these bearings has changed through the years and can have a large impact on the overall performance of your diesel engine.
Today we're taking you through the different materials and how they can help to prevent premature camshaft bearing failure.
Running into problems with your camshaft bearings? Our ASE Certified Technicians can help!
About Camshaft Bearing Material
For a long time, most camshaft bearings were made with babbitt. This material consists of mostly tin and lead. Similar to solder, it is a soft and slippery material. Babbitt was used widely due to its ability to withstand harsh conditions and hold up under foreign particle contamination, misalignment, and marginal lubrication on start up.
Recently, though, diesel engines have been pushed to higher operating temperatures and valvetrain loads. This begins to limit the materials that can be used for camshaft bearings. Babbitt, for example, doesn't hold up as well under these harsher conditions because of its low strength.
Babbitt bearings put into these conditions can cause lining extrusion or fatigue. You can tell this is happening by the craters that appear in the bearing surface where the lining has flaked away.
Because of these higher demands in both load and temperatures, many modern engines have abandoned babbitt as a liner material. Instead, modern diesel engines favor a camshaft lining of aluminum alloy. This alloy is stronger than babbitt and has the capacity to withstand the harsher operating temperatures of the newer engines.
This strength comes at a cost, though. Aluminum alloy doesn't have the same forgiving nature as babbitt, and is more susceptible to dirt, misalignment, and marginal lubrication. This is not an uncommon trade-off, though, when looking for materials suited to current engine operating conditions, especially when it comes to higher loading. With higher loading, precision is key to keep the engine reliable. Cleanliness, alignment clearances, journal surface finishes, and lubrication are all vital to maintain optimal operating conditions.
Looking for more info on diesel engine camshaft bearings? Read our blog, Camshaft Bearings Explained!
Optimizing Aluminum Alloy Camshaft Bearing Performance
Here are some things that you can do to help your aluminum diesel engine camshaft bearings perform their best:
Ensure that there is sufficient clearance during the initial install. These aluminum alloy bearings will not wear to create there own clearance like the babbitt ones do, because the material is so much stronger. Minimum clearance should be .002" for stock engines and .003" for high performance. Because of the stack of tolerances on the block, shaft, and bearing, it is impossible to control clearance to this range in the manufacture of the bearing. You have to measure carefully during install.
It's not recommended that you hone the ID of the cam bearings to increase the clearance. This can lead to grit in the surfaces, causing shaft wear. The most practical way to adjust camshaft journal diameters is to grind the journal. Regardless of whether or not you have it ground to provide extra clearance, the bearing journals should be polished to the correct surface finish, with the camshaft rotating in the direction it rotates during operation.
Want to know more about how a camshaft bearing can fail? Check out our camshaft bearing failure analysis!
Alignment also plays a large role in the operation of your camshaft bearings. If a block has to have its main bearing bore alignment corrected because of distortion it will probably have had cam bearing bore distortion, too.
It's important to avoid shaving the bearings on install. This could cause metal buildup between the bearing OD and housing bore, leading to a reduction in the all important clearance. To prevent this, ensure that there is a proper lead-in chamfer before install (20-30 degrees). If there aren't grooves behind the cam bearings make sure that the oil holes line up between the bearings and the block.
If it does have a groove, the bearing should be installed with the oil hole at the 2 o'clock position when viewed from the front to introduce the proper oil into the clearance space.
It's important to keep your diesel engine camshaft bearings operating at their best to maintain optimal engine performance. Talk to our ASE Certified Technicians if yours are causing you problems, or if you have any other diesel engine parts needs. Call them at 844-304-7688, or request a quote online!
Originally Posted October 7, 2015, Edited February 21, 2020