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Subaru EJ257 main bearing oil clearance

Practical Engine Building

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I am rebuilding an EJ257 with the goal of achieving stock engine performance. I have installed King MB5382XPG main bearings and will be using a new Subaru factory crankshaft. The Subaru rebuild manual calls for oil clearance on the main bearings of 0.00039-0.0012” while King recommends 0.001” of clearance per inch of shaft diameter. Main journal diameter is 2.362” making a target oil clearance of 0.0024”, twice what the factory recommends. I measured with the bore gauge and found clearances between 0.0023-0.0026”. I’m wondering which guideline I should follow and if I go with the larger clearances should I use higher viscosity oil or perhaps a higher capacity oil pump?

Clearance depends significantly on what you're going to be using the engine for, and the power/torque expected.

This specific enquiry has come up multiple times - a simple search should narrow it down for your specific application.

You'll also want to make sure you don't set the engine up in a manner that you can't provide it with sufficient oil flow due to excessive bearing clearances.

We usually reply within 12hrs (often sooner)

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