Hello everyone,

New to the mini scene and finally decided to join a forum to hopefully get some insight from others who are more familiar.

I am in the process of rebuilding what I believe is called N12 R56 engine. So working on a 2007 Base Hatch Cooper.

THE PROBLEM
I have looked and bought two different sets of pistons but even though they are advertised as fitting the base model engine, the wrist pin on the forged pistons are too large for my stock rods.
Does anyone know of any 77.5mm pistons (forged or not) for these engines?




The D difference is noticeable in this pic





The block after machining





The reason for all this

 

Come on guys, nobody have any insight? I've contacted CP Carillo and they said they can make to order but looking at BIG $$$

 

I don't know why an aftermarket builder wouldn't make wrist pins to fit the stock conn rods. I'd return the piston sets and look for a set that's made to fit the stock rods.

Either that, or do the piston makers have matching conn rod sets?

 

I don't know anybody that would install forged pistons on a 118hp engine, there's absolutely zero market for such a build. The reason it costs so much is because it's custom.

 

I read somewhere that Mahle made the OEM set. Maybe they have 77.5 stuff available?

Does your existing piston source also sell matching rods? 'Course, if they do, they probably won't fit the crank ---lol.

Can the Mini dealership get oversized pistons? As stated above, there's no need for a forged set on the N12. Rebuild as needed, then follow good maintenance practices --- oil and filter changes often, and don't drive it like an "S" version.

And when you finally find a set that fits together, be sure to do a trial fit with one set and rotate a couple times to ensure rod - piston skirt clearance. Not all pistons are interchangeable with OEM rods --- skirts too, not just wrist pins.

 

Thanks for the pointers!


- Rod/skirt clearance is definitely a worry
- I could get "S" con-rods but not sure how that would fit on the crank and also what the new stroke would be


I will check with Mahle. I would like to do something different, perhaps down the road go forced induction...we will see what I can figure out with the pistons first.