Crankshaft Main Bearing Set for FA20/4U-GSE Engines ⚙️

Keep your boxer engine spinning smooth and quiet. These precision main bearing shells support the crankshaft, hold correct oil clearance, and keep oil pressure stable. Ideal for fresh builds, bottom-end refresh, or when mileage, track use, or low oil episodes have marked the journals. 🛠️

Why this part is needed 🚗

Main bearings center the crank, cut friction, and control heat. Proper clearances protect journals, prevent scoring, and keep the hydrodynamic oil film intact for long engine life.

How it works

Thin-shell, tri-metal or aluminum bearings ride on a pressurized oil wedge. The shells lock into the block and caps via tangs, while oil grooves and feed holes deliver steady lubrication. Micron-level sizing keeps the crank floating on oil, not metal.

What happens if worn or damaged ❗

Symptoms include hot idle knock, low oil pressure light, glitter in oil, and vibration. Continued driving can spin a bearing, wipe a journal, seize the crank, or throw a rod—turning a service job into a full rebuild.

Install tips from a pro

• Measure journals and bores; select correct grade/oversize
• Plastigage clearances; verify crank endplay
• Use assembly lube; torque caps in sequence
• Keep everything ultra-clean; never mix caps

• 86
• Gt86/86
• Scion Fr-S/86