Main bearing set 0.25 oversize inner for Porsche 911 2.7L / 911 Turbo 930  ❭  91110190250

Main Bearing Set 0.25mm Oversize Inner - Standard Outer

Main bearings support the crankshaft within the crankcase and provide the accurately controlled running clearance required for reliable lubrication and smooth crankshaft rotation. This set is intended for engines requiring a 0.25mm oversize inner bearing specification and is supplied with 12 bearings plus 2 thrust bearings.

Fits:

• Porsche 911 1974-1977 2.7L / 1976-77 3.0 Carrera
• Porsche 911 1975-1977 3.0L Turbo (930)

Diagram Ref No 23 and 24

Specification: 0.25mm oversize inner / standard outer
Contents: 12 bearings + 2 thrust bearings

What Do the Main Bearings Do?

Main bearings support the crankshaft as it rotates within the engine. Pressurised oil creates a lubricating film between the crankshaft journals and bearings, reducing friction and wear.

The thrust bearings also control axial movement of the crankshaft.

Why Do Main Bearings Wear?

Bearing wear can result from:

• High engine mileage
• Low oil pressure or oil starvation
• Contaminated engine oil
• Incorrect bearing clearances
• Crankshaft journal wear
• Engine overheating
• Previous internal engine damage

The cause of abnormal bearing wear should always be identified during an engine rebuild.

Why Use 0.25mm Oversize Bearings?

This is not a standard-size bearing set.

The 0.25mm oversize inner specification is intended for an engine where the crankshaft has been measured or machined to require this corresponding bearing size.

Accurate crankshaft and crankcase measurements are essential before ordering. Oversize bearings should not be selected simply because the existing bearings are worn.

When Should Main Bearings Be Replaced?

Main bearings should be inspected during an engine rebuild and replaced if they show scoring, excessive wear, surface damage, incorrect clearance or evidence of oil starvation.

Crankshaft journals, bearing housings, oil passages and thrust surfaces should also be inspected before assembly.

Main Bearing Sets

Correct main bearing selection is essential when rebuilding an air-cooled Porsche flat-six engine. The bearings support the crankshaft, maintain the required oil clearance and help ensure reliable lubrication throughout the engine.

This OE Match 0.25mm oversize inner main bearing set is designed for Porsche 911 2.7 and 930 Turbo 3.0 engines requiring this specific bearing dimension.

Always measure the crankshaft journals and crankcase accurately before selecting standard or oversize bearings. Design911 supplies Porsche main bearings, thrust bearings and associated engine rebuild components for classic air-cooled Porsche applications.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

91110190250

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