P-Series Bearings

These are not to be confused with the standard passenger car and light truck parts for the same retention applications which also have a “P” suffix letter. These high performance parts have unique core part numbers different from the standard parts for the same application. P series parts are the oldest series of Clevite high performance bearings. The rod bearings in this series typically have the greatest amount of eccentricity. Most
rod bearings are available either with or without dowel holes for use in aluminum rods. Most P series main sets are full grooved to maximize oil flow to the rod bearings. Both rods and mains have high crush for maximum retention, and a reduced overlay thickness to prevent overlay fatigue, sometimes referred to as hen tracking.

High crush for better seating and retention. High eccentricity accommodates rod bore distortion. Hardened steel backing for greater strength. Strong, extra-thin overlay to withstand high loading and resist flaking. Grooved lower mains maintain 360 degree oiling.
Rod bearings use a hardened steel back for added strength and resistance to fretting. Extra
clearance rod bearings are available for .001” additional clearance and select fitting. Use the P series rods where extremely high RPM’s cause severe rod bore close-in. This is typically indicated by nearly full parting line to parting line shaft contact with bearings having less eccentricity. Use P series mains where higher eccentricity is desired to narrow bearing contact patterns and to provide increased oiling to rod earings. Rod bearing oil starvation is typically indicated by polishing and smearing of the bearing surface, possibly accompanied by discoloration predominantly concentrated at the axial center of the bearings.

Bearing Material: Tm-1 (Steel Backed copper-lead Matrix with overlay)
Clevite Part # CB-1589P
Available Sizes STD, .25mm, .50mm

Standard Shaft Diameter 1.9670/1.9675
Vertical Oil Clearance 0.0004/0.0024 *crazy thin film*
Max Wall 0.0594
Brg. O.D. or Housing Bore 2.0866/2.0871
Max Length 0.7870

Main Bearing Set
Bearing Material: Tm-1 (Steel Backed copper-lead Matrix with overlay)
Clevite Part # MS-1949P
MS-3341P #1-2-4-5
MS-3342P(F) #3
Available Sizes STD, .25mm, .50mm

Standard Shaft Diameter 2.3606″/2.3615″
Vertical Oil Clearance 0.0005″/0.0038″
Max Wall 0.0722″
Brg. O.D. or Housing Bore 2.5063″/2.5068″
Max Length 0.7480″

Standard Shaft Diameter 2.3606″/2.3615″
Vertical Oil Clearance 0.0005″/0.0038″
Max Wall 0.0722″
Brg. O.D. or Housing Bore 2.5063″/2.5068″
Max Length 1.0610″

When measuring bearings, measurements should always be taken at 90 degrees to the parting line to determine the minimum clearance.
If measuring the bearing wall thickness, use a special micrometer with a ball anvil to fit the curvature of the bearing I.D. The best way to determine bearing clearance is to measure the bearing ID with the bearings installed in the housing and the bolts torqued to the specified assembly torque. Use a dial bore gage to measure the bearing ID at 90 degrees to the parting line, then subtract shaft size from bearing ID to determine clearance. If the dial bore gage is zeroed at the actual diameter of the
crankshaft journal to be installed, the dial bore gage will then read clearance directly and the subtraction calculation can be eliminated. About .001” clearance per inch of shaft diameter is a good rule of thumb for clearance. Increasing the total by about .0005” will add a little margin of safety when starting out, especially for rods.

Example: .001” X 2.100 = .0021” then add .0005”, so starting out set clearance at .0026” for a 2.100 shaft.

If clearance adjustments need to be made, use either an extra clearance part for more clearance, or an undersize part for less clearance. It is permissible to mix sizes if less than .001” adjustment in clearance IS desired. When mixing sizes for select fitting never mix parts having more than .0005” difference in wall size, and always install the thickest wall shell in the upper position if installing a rod bearing, or the lower position if installing a main bearing. When working with a reground shaft always measure assembled bearing ID’s first and have the shaft sized to produce the desired clearance since there are no extra clearance parts available for undersize shafts. When measuring a bearing ID or wall thickness avoid measuring at the parting line. As the “Bearing Design” diagram illustrates there is a parting line relief machined into nearly all bearing shells. This relief is to allow for any mis-match between upper and lower shells due to tolerance differences, or possibly resulting from cap shift or twist during assembly. To determine bearing wall eccentricity or assembled bearing ID ovality, measure at a point at least 3/8” away from the parting line.

When installing any bearing DO NOT ATTEMPT TO POLISH THE BEARING RUNNING SURFACE WITH ANY TYPE OF ABRASIVE PAD OR PAPER. Bearing overlay layers are extremely soft and thin, typically .0005” on high performance parts. These thin layers can easily be damaged or removed by abrasive media. Because the overlay layer is electroplated, it may exhibit microscopic plating nodules that make it feel slightly rough. The nodules are the same material as the rest of the plated layer and will quickly be flattened by the shaft. Bearing surfaces can be lightly burnished with solvent and a paper towel if desired.


About awdaltima

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