How does a crank grind and polish improve performance?

[thexav]

One mod I can't get my head around is the crank grind and polish.

How does grinding the crank and polishing it improve an engines performance?

Can you just grind it, without polishing? Or can you just polish it without grinding it?

 

[Lunchmoney]

Is this a new dance craze?

the crank grind and polish

 

[obi_waynne]

Polishing a crank removes small imperfections, tiny surface scratches imperfections and cracks and reduces the amount of oil that sticks to it.

As the crank splashes in the oil the smoother it is the less drag is created.

Older discussion on this topic is here.

What are the benefits of a polished crank

What have you discovered to be the benefits of a polished crank? What other crank mods are worth thinking about doing? What is a nightrided, knife-edged crank?

www.torquecars.com

 

[JollyFatMan]

Polishing a crank removes small imperfections, tiny surface scratches imperfections and cracks and reduces the amount of oil that sticks to it.

As the crank splashes in the oil the smoother it is the less drag is created.

Older discussion on this topic is here.

What are the benefits of a polished crank

What have you discovered to be the benefits of a polished crank? What other crank mods are worth thinking about doing? What is a nightrided, knife-edged crank?

www.torquecars.com

So do you grind the entire crank or just the journals? I'd imagine that the crank mass would need balancing after.

A little bit off topic but when you remove mass from the crank, does that impact the dynamic balance of the engine as a whole given that your piston and conrod mass remains the same. Or do you adjust them too?

 

[TCJBOLDIE]

So do you grind the entire crank or just the journals? I'd imagine that the crank mass would need balancing after.

The crankshaft will only need grinding IF the journals are damaged. they will have to be ground to suit whatever undersize bearings that are available. The journals are the parts that the bearings are fitted to and they are normally the only sections of a crankshaft that are machined unless it is out of balance and then weight is machined off the counterweights to get it dynamically balanced .

Linishing is a process to mirror polish the journals to remove any defect that could damage the new bearings.