Y’all, hoping you can help. I’m looking for drop-in pistons same bore size as stock that will get me to the JCW compression 10:1. So these would be aftermarket upgrades, new rings, etc. I can’t find them online maybe they don’t exist? Or maybe I go with 10:5 drop in 77mm and install a way thicker head gasket??? Lastly, maybe this is the issue, I’m not building a race car. I just want to *slightly* upgrade my internals over stock factory. Right now my N18 motor is pulled and stripped. Would be foolish not to do upgrades with motor out right? TIA :-)

 

Could you not just buy JCW pistons and then be done with it? The bore and stroke are identical to the standard N18 motor. The pistons seem to be readily available - for example, fleabay listing.......

https://www.ebay.com/itm/37588269583...6e9073b88186ea

 

Thanks for jumping in I do appreciate it.
Aftermarket 77mm bore 10:1 are going to be stronger and cheaper than OEM JCW pistons, right?

 

The OEM MINI JCW pistons are running ~$350 EACH. You can buy an entire set of Supertech JCW pistons for <$700.

Supertech makes nice stuff.

 

Alrighty. So…. If im not going to track, but I also won’t use the Mini as my DD… now what? The forged pistons with too many cold starts can cause some longevity issues with piston slap?

No track. Weekend canyon carving with some spirit! No winters.

And my motor is out and stripped so I gotta do something :-)

 

The Cooper S N18 motor has forged pistons from the factory. Same manufacturer for both the S and JCW pistons, the difference was in the crown design, that's how they lowered the compression with the same bore/stroke.

So you're getting forged pistons either way, friend.

 

many thanks for helping me understand that both S and JCW were assembled factory with forged pistons. Case closed eh? Now onto the Rods, valves, seals, springs, and bearings :-)