Main bearing size explanation please (1 Viewer)

[Don Pedro]

Mechanic says I need ".50" main bearing set for my 85 FJ 60 2f. I am assuming in photo the .50 is in millimeters but I am curious as to what the "U/S" in front of it signifies. A Toyota online parts guy says it means "undersized" but this leaves me confused because the engine is being bored 1.00 (.40) over. Can any of you gentlemen set my mind at ease with a simple explanation? Thanks!

 

[RockDoc]

When the cylinders are machined the bore gets bigger in diameter - oversize pistons and rings are needed.

When the crank journals are machined they get smaller in diameter - undersized bearings are needed.

 

[Don Pedro]

When the cylinders are machined the bore gets bigger in diameter - oversize pistons and rings are needed.

When the crank journals are machined they get smaller in diameter - undersized bearings are needed.

Thank you Doc, even I can understand that explanation!

 

[Spike Strip]

Even with these massive crankshafts .50 undersize is kind of a lot. Ask the machinist about 'Radius' on the CS.

 

[Don Pedro]

Even with these massive crankshafts .50 undersize is kind of a lot. Ask the machinist about 'Radius' on the CS.

Thanks...will run it by him tomorrow...