Clevite bearings...Regular or "H series".
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HEAVY DUTY CAM BEARING MATERIALS FOR VARIOUS APPLICATIONS
In the last decade or so engine development has increased dramatically. Each time an existing engine is revised or a new engine is developed, it pushes the limits of what its predecessor could produce both in horsepower and torque as well as fuel efficiency. With these gains, comes an increased load on the internal parts of these engines. One of these parts that are continually asked to perform under greater and greater pressures is the cam bearing. In engine configurations such as V6’s and high RPM 4 cylinders, the cam bearing is a vital link along the path of the engines oiling system. If a cam bearing wears out prematurely the engine loses some of its oil pressure, which we all know can lead to premature engine failure. Other problems, which can be caused by premature cam bearing wear, are excessive cam lobe runout, improper timing, and generally poor running conditions. This is where strength and durability become key issues. This is why, in most applications, the O.E. manufacturers have turned to higher performing cam bearing materials.
Traditional babbitt can only withstand up to 1800 psi. Clevite 77s’ AL-3 material can withstand up to 5000 psi. Quite a difference. When trying to adapt babbitt to an application that requires a more durable material, extra oil grooves are needed on the outside diameter of the bearing itself to help get oil to the rest of the engine. This only addresses the oil starvation symptom inherent to the real problem of premature wear. All of the other symptoms that were listed above still occur with the right material for the job, such as Clevite 77’s AL-3, these extra oil grooves aren’t needed at all. In fact this gives more bearing contact area to the block to help in transferring heat away from these parts and
PREVENTING PREMATURE CAM BEARING FAILURE
For many years, nearly all camshaft bearings were manufactured with a lining of babbitt. Babbitt is a soft slippery material made up primarily of lead and tin and is quite similar to solder. As a bearing surface layer, babbitt possesses the desirable properties necessary to survive under adverse conditions such as foreign particle contamination, misalignment and marginal lubrication on start up. The trend in modern engines has been toward higher operating temperatures and higher valvetrain loads. Babbitt is limited in its ability to survive under these conditions due to its relatively low strength. When babbitt cam bearings are installed under these demanding conditions, the lining may extrude or fatigue. Fatigue can be identified by craters in the bearing surface where sections of lining material have flaked out. To meet the demands of higher loads and operating temperatures in modern engines as well as the requirements imposed by high performance, babbitt has been replaced by an alloy of aluminum. This aluminum alloy is much stronger than babbitt and will withstand several times the load. However, this added strength is obtained at the expense of some of the more forgiving properties of babbitt. The aluminum alloy is harder, making it somewhat less compatible with dirt, misalignment and marginal lubrication. This is typical of the compromises or trade offs that are frequently necessary when selecting a bearing material to suit the requirements of a specific application and in this case, higher loading. Typically, whenever a higher level of loading is encountered, greater precision is required to maintain reliability. Conditions such as cleanliness, alignment, clearances, journal surface finishes and lubrication must all be controlled more closely. Following are some recommendations to help optimize performance when using aluminum alloy camshaft bearings.
Sufficient clearance is necessary in the initial installation. These stronger bearings will not wear in rapidly to make their own clearance like softer babbitt materials. Minimum clearance should be .002” for stock engines and .003” for high performance. Optimum clearance range for high performance applications is .003” to .004”. Because of the stack up of tolerances on the block, shaft and bearing it is impossible to control clearance to this range in the manufacture of the bearing alone. Clearances must be measured at installation. Honing the ID’s of cam bearings to increase clearance is not recommended because hone grit may become embedded in bearing surfaces that will cause shaft wear. Bearing ID’s may be reamed, but the most practical means is to adjust camshaft journal diameters by grinding the journal. Even if not ground to provide additional clearance, camshaft bearing journals should be polished to the proper surface finish with the camshaft rotating in the same direction it will rotate in the engine. Like clearance, alignment is also extremely important especially for high performance applications. Any blockthat has needed to have its main bearing bore alignment corrected due to distortion is likely to have experienced cam bearing bore distortion as well. Adequate clearance can help compensate for minor misalignment of less than .001”. Installation of bearings into the block must be done with care to avoid shaving metal off the backs of the bearings. This galling action may cause a build-up of metal between the bearing OD and the housing bore which will result in a reduction in clearance. To prevent galling, check housing bores for a proper 25 to 30 degree lead-in chamfer before installing cam bearings. On blocks without grooves behind the cam bearings, care must be taken to insure that oil holes line up between the bearings and block. Where the block has a groove behind the bearing, the bearing should be installed with the oil hole at the 2 o’clock position when viewed from the front for normal clockwise camshaft rotation. This will introduce oil into the clearance space outside of the loaded area and allow shaft rotation to build an oil film ahead of the load.
On certain modified performance applications Clevite 77 also offers a TriMetal cam bearing material (TM-1)that provides even greater strength and durability. These cam bearings are able to withstand loads in excess of 8,000 psi, while providing surface characteristics that are very forgiving and conformable.
Rich
In the last decade or so engine development has increased dramatically. Each time an existing engine is revised or a new engine is developed, it pushes the limits of what its predecessor could produce both in horsepower and torque as well as fuel efficiency. With these gains, comes an increased load on the internal parts of these engines. One of these parts that are continually asked to perform under greater and greater pressures is the cam bearing. In engine configurations such as V6’s and high RPM 4 cylinders, the cam bearing is a vital link along the path of the engines oiling system. If a cam bearing wears out prematurely the engine loses some of its oil pressure, which we all know can lead to premature engine failure. Other problems, which can be caused by premature cam bearing wear, are excessive cam lobe runout, improper timing, and generally poor running conditions. This is where strength and durability become key issues. This is why, in most applications, the O.E. manufacturers have turned to higher performing cam bearing materials.
Traditional babbitt can only withstand up to 1800 psi. Clevite 77s’ AL-3 material can withstand up to 5000 psi. Quite a difference. When trying to adapt babbitt to an application that requires a more durable material, extra oil grooves are needed on the outside diameter of the bearing itself to help get oil to the rest of the engine. This only addresses the oil starvation symptom inherent to the real problem of premature wear. All of the other symptoms that were listed above still occur with the right material for the job, such as Clevite 77’s AL-3, these extra oil grooves aren’t needed at all. In fact this gives more bearing contact area to the block to help in transferring heat away from these parts and
PREVENTING PREMATURE CAM BEARING FAILURE
For many years, nearly all camshaft bearings were manufactured with a lining of babbitt. Babbitt is a soft slippery material made up primarily of lead and tin and is quite similar to solder. As a bearing surface layer, babbitt possesses the desirable properties necessary to survive under adverse conditions such as foreign particle contamination, misalignment and marginal lubrication on start up. The trend in modern engines has been toward higher operating temperatures and higher valvetrain loads. Babbitt is limited in its ability to survive under these conditions due to its relatively low strength. When babbitt cam bearings are installed under these demanding conditions, the lining may extrude or fatigue. Fatigue can be identified by craters in the bearing surface where sections of lining material have flaked out. To meet the demands of higher loads and operating temperatures in modern engines as well as the requirements imposed by high performance, babbitt has been replaced by an alloy of aluminum. This aluminum alloy is much stronger than babbitt and will withstand several times the load. However, this added strength is obtained at the expense of some of the more forgiving properties of babbitt. The aluminum alloy is harder, making it somewhat less compatible with dirt, misalignment and marginal lubrication. This is typical of the compromises or trade offs that are frequently necessary when selecting a bearing material to suit the requirements of a specific application and in this case, higher loading. Typically, whenever a higher level of loading is encountered, greater precision is required to maintain reliability. Conditions such as cleanliness, alignment, clearances, journal surface finishes and lubrication must all be controlled more closely. Following are some recommendations to help optimize performance when using aluminum alloy camshaft bearings.
Sufficient clearance is necessary in the initial installation. These stronger bearings will not wear in rapidly to make their own clearance like softer babbitt materials. Minimum clearance should be .002” for stock engines and .003” for high performance. Optimum clearance range for high performance applications is .003” to .004”. Because of the stack up of tolerances on the block, shaft and bearing it is impossible to control clearance to this range in the manufacture of the bearing alone. Clearances must be measured at installation. Honing the ID’s of cam bearings to increase clearance is not recommended because hone grit may become embedded in bearing surfaces that will cause shaft wear. Bearing ID’s may be reamed, but the most practical means is to adjust camshaft journal diameters by grinding the journal. Even if not ground to provide additional clearance, camshaft bearing journals should be polished to the proper surface finish with the camshaft rotating in the same direction it will rotate in the engine. Like clearance, alignment is also extremely important especially for high performance applications. Any blockthat has needed to have its main bearing bore alignment corrected due to distortion is likely to have experienced cam bearing bore distortion as well. Adequate clearance can help compensate for minor misalignment of less than .001”. Installation of bearings into the block must be done with care to avoid shaving metal off the backs of the bearings. This galling action may cause a build-up of metal between the bearing OD and the housing bore which will result in a reduction in clearance. To prevent galling, check housing bores for a proper 25 to 30 degree lead-in chamfer before installing cam bearings. On blocks without grooves behind the cam bearings, care must be taken to insure that oil holes line up between the bearings and block. Where the block has a groove behind the bearing, the bearing should be installed with the oil hole at the 2 o’clock position when viewed from the front for normal clockwise camshaft rotation. This will introduce oil into the clearance space outside of the loaded area and allow shaft rotation to build an oil film ahead of the load.
On certain modified performance applications Clevite 77 also offers a TriMetal cam bearing material (TM-1)that provides even greater strength and durability. These cam bearings are able to withstand loads in excess of 8,000 psi, while providing surface characteristics that are very forgiving and conformable.
Rich
Last edited by rskrause; Nov 7, 2006 at 06:32 AM.
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Posts: 10,745
From: Buffalo, New York
Banned
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Posts: 6,661
From: LA (lower Alabama)
If ya measure carefully,the cam bearings are streight in a factory block.
They were line bored AFTER being installed.Ya can't have this done by a normal shop.
Ya need to check every journal with new brgs and cam.
I would use Clevitte "H",ACL,Durabond and make SURE they are clocked right.
They were line bored AFTER being installed.Ya can't have this done by a normal shop.
Ya need to check every journal with new brgs and cam.
I would use Clevitte "H",ACL,Durabond and make SURE they are clocked right.
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Joined: Aug 2003
Posts: 267
If ya measure carefully,the cam bearings are streight in a factory block.
They were line bored AFTER being installed.Ya can't have this done by a normal shop.
Ya need to check every journal with new brgs and cam.
I would use Clevitte "H",ACL,Durabond and make SURE they are clocked right.
They were line bored AFTER being installed.Ya can't have this done by a normal shop.
Ya need to check every journal with new brgs and cam.
I would use Clevitte "H",ACL,Durabond and make SURE they are clocked right.
Banned
Joined: May 2003
Posts: 6,661
From: LA (lower Alabama)
Are they in line ??
Hard to tell. Just because the cam turns don't get it.
This is more a problem when the spring pressure goes UP,but a problem anytime if out too far.
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Dave88LX
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May 2, 2003 07:53 PM