Tri-metal big end bearings, BMW M3 E30 S14B23 S14B25

The ACL RACE and KING RACING tri-metal big end bearing sets for the S14 engine contain 8 bearings.

Technical specification

• Crankshaft crank pin diameter (min/max): 47.975 / 47.991mm
• Big end housing diameter (min/max): 52.000 / 52.015mm
• Max thickness: 1.993mm
• Size(s): standard, standard with HX clearance, +0.025 or +0.25mm
• Anti-friction coating: none
• References: 4B1568, 4B1568H-STD, 4B1568HX-STD, 4B1568H-.025, 4B1568H-.25

ACL Race Series tri-metal bearings are made to exacting tolerances. CNC machining works to the micron, followed by metrology checks on the diameter, the thickness and the width of every ACL Race Series tri-metal bearing. That is how these bearings give a reliable, consistent fit in your performance engine. They are in fact built up from 4 layers:

• SAE1010 steel on the outside
• 0.3mm copper alloy
• 0.0001mm nickel
• Copper alloy from 0.013 to 0.018mm

This choice of materials, combined with the manufacturing processes, makes ACL Race Series tri-metal bearings stronger against increases in power, torque and engine speed. Their compression strength keeps your engine reliable even on heavily boosted turbo or supercharger builds, or on sharp engines running high rpm.

Technical specification

• Crankshaft crank pin diameter (min/max): 47.98 / 47.99mm
• Big end housing diameter (min/max): 52.00 / 52.01mm
• Max thickness: 1.994mm
• Size(s): standard, standard with HX clearance, +0.026 or +0.25mm
• Anti-friction coating: none
• References: CR4596, CR4596XP, CR4596XP STDX, CR4596XP.026, CR4596XP0.25

King Racing has been designing and manufacturing high performance, high quality bearings since 1960. Beyond its production machinery, King Racing relies on simulation software to analyse the thermodynamics, the dynamics and the elasto-hydrodynamics of its bearings. King Racing tri-metal big end bearings are made from pMax Black, a tri-metal alloy 24% stronger than any existing tri-metal big end bearing.

King Racing bearings are built up from 3 to 4 layers, depending on the application:

Outside: steel Intermediate: lead bronze Inside: babbitt with a high copper content Anti-friction coating with lubricant and ceramic additives