Bearings

1. Why Performance Bearings Matter

Standard OEM-style bearings are engineered for factory clearances and moderate operating conditions. Performance engines, particularly those built by Butler, require different specifications:

• Larger Clearances: Performance engines typically require slightly larger main and rod bearing clearances (often 0.0025 to 0.003 for rods/mains) to accommodate the higher heat, higher RPM, and increased oil flow from high-volume oil pumps. Performance bearings are designed for these specific clearances.

• Load Handling: High-horsepower Pontiac strokers place immense loads on the bearings. Performance bearings feature materials and construction that can withstand these extreme forces without fracturing or failing.¹

• Material Strength: Modern performance bearings are often constructed with superior alloys (like tri-metal materials) and specialized coatings to handle the stress of high-output environments.

2. Clevite H-Series: The Workhorse

For virtually all high-performance street/strip and race applications, Butler Performance relies heavily on the Clevite H-Series performance bearings.

• Design: Clevite H-Series bearings are tri-metal construction (steel backing, copper-lead intermediate layer, and a lead-tin-copper over-plate).² They are designed with slightly more eccentricity (the oil film thickness variation) and reduced crush to deliver optimal performance under high engine loads.

• Strength: They utilize a hardened steel back and a thinner overlay for superior load-carrying capacity compared to standard bearings.

• Application: Butler uses the H-Series for the main bearings and the rod bearings in their 461cuin to 505 and 535cuin stroker short blocks, ensuring the vital main and rod journals are protected.

3. King Bearings: High-End Alternatives

Butler also utilizes King Engine Bearings, particularly their XP Series, as a premium alternative for builders seeking maximum performance and load capacity.

• XP Series: These are specialized, high-load tri-metal bearings designed with a harder construction specifically for racing and extreme conditions.⁴ They often feature King's proprietary Max-Clutch bearing material.

• Main Journals: King bearings are frequently used to address the different main journal sizes found in Pontiac blocks:

  • 3.00-Inch Mains: Used on 326, 350, 389, and 400 blocks.

     

4. The Critical Role of Clearances

Simply buying the best bearing is only half the battle. Butler’s engine builders emphasize that the final running clearance is paramount.

• Precision Measurement: Every Butler-built engine has its clearances checked and recorded, often using a micrometer and bore gauge (or plastigage for initial mock-up).

• Undersize Options: To achieve the precise .0025in to .003in running clearance, Butler stocks and utilizes undersize bearing options (e.g., 0.001in or 0.002in undersize) which can be mixed and matched with standard sizes to hit the exact target clearance.

• Thrust Bearing: Special attention is paid to the thrust bearing (main bearing #4 in a Pontiac V8) to ensure the proper crankshaft end play is achieved—a critical factor for engine longevity that prevents the crank from moving excessively forward or backward.

By sourcing high-quality Clevite and King bearings and meticulously setting running clearances, Butler Performance ensures the foundation of every high-horsepower Pontiac V8 is protected against the extreme internal loads of performance driving.