You may need bigger injectors for the bigger bore so it doesn't run lean.

Fit your rings to the pistons and check the clearance in the ring grooves. One of the reasons for high oil consumption is worn ring grooves , which cause a pumping action as the rings move up and down in the worn groove. Check manual for max clearance allowed. If pistons and rings are within the recommended values, check all 4 pistons, Then you could buy a set of 0.5 mm oversize rings and very carefully gap them in the bores by filing or grinding the ring ends with a dremel and thin cutting wheel. Use the side of the wheel. Grind very carefully until the ring gap comes into tolerance. You can achieve the minimum tolerance very easily with oversize rings gapped in slightly worn standard bores. Hone the other 2 cylinders, to allow rings to bed in. Honing takes very little out of the bores. Don’t overdo it. Just take off the glaze. I did this on an engine with worn bores with good results. It didn’t burn oil and had good compression.

Your doing the right thing having it rebored I can't see any point in putting it back together when you know it's showing signs of wear I wish you all the best with it

You've made the right call!

You're doing the right thing. The tolerance values are there for a reason and it would not have been any good with lower comp and oil burning.

I understand the worry about the ring gap, but wouldn't aftermarket rings be an option? This would allow you to adjust the gap within tolerance restoring it to factory spec. My only real concern about the larger bores would be the amount of piston slap but can't make an assessment with only the bore size. The piston diameter would be required. Note aftermarket often have high piston bore gaps to allow for expansion under higher heat loads and material differences. At the end of the day you need to keep the gap as small as possible but large enough to avoid binding.

Sorry to hear the bad news. However, I believe you have made the right choice. Fingers crossed for you and can’t wait to see it running again.

Excellent break down. Thank you.

Some bmw petrol engines have a special coating on the bores. So need to be careful in regard to honing or reboring. Also don't rely on a Haynes manual. Errors are common. You need the BMW TIS manual.

Yes, 80k miles on a petrol, get 1st rebore size for sure. Great content! I have watched enough to know you do every job the right way. You would not be happy rebuilding an oil burner. Hope you can move on the standard pistons and rings.

Having just blown the engine on my Autosolo car.. I can sympathise. Just do it properly, it's worth it if you're going to keep the car.

Yes I would do it right and bore 0.50 mm.

Sorry to hear dude

You need bigger ring gaps with turbo charged engine to cope with the compression from forced induction, so if your going to tune / remap and up the boost you would want a bigger ring gap

Haha I did exactly the same thing with a n12. I tried standard rings -massive gaps. Did you notice the lower composite oil scraper ring they go spongey. On aftermarket ring sets this is different standard steel type. We bought a 2nd hand block and wear was exactly the same. glad someone is doing some proper content on the issue. I’m changing my oil every 4k after oversize pistons fitted see how long it lasts. Theories as to why they wear: service interval too high, owners don’t check oil and dipstick hard to read, no early warning oil light, when engine overheats due to bmw plastic thermostat housing and pipe cracking the engine overheats leading to piston bore wear. Such a shame bmw ruined the pug tu5 😂 My personal suggestion is fit a Peugeot tu5 engine or Honda engine. Avoid all bmw plastic crap at all costs.

Please get a video of the rebore at an engineering firm along with costs for new pistons etc. It will make great content.

Have you checked the original ring gaps? MINI for a while did oversized rings and pistons as options and when a block failed quality control it would be moved to oversized and not thrown away. That was from a BMW tech a while ago when I rebuilt my engine. His advice was to always measure first before buying new pistons for that reason. If it was wear there would be a lip usually. E.g. the top of the cylinder would be normal and 50mm down would be greater size.

UM.....precision is perfection.UM.....I have 225.000 miles on MY N16 normally aspirated, less heat yett difficult to watch temps. AN viscosity unburned fuel wash.carbon management preparation solutions and then there's the plastic.....well...she is well USED my baby.

Honestly, you could just hone it and call it a day. The ring gap might be slightly larger than factory but nothing to worry about as you'll have new oil control rings, new compression rings, and a rebuilt top end. Refreshing old engines with just the head, rings and bearings was something that people do if they have a half decent working engine. Heck, if you put boost to a "loose" engine, it doesn't blow up as fast as a "tight engine because bigger engine tolerances are good for thermal expansion. Emissions has really pushed auto makers to make engines"tight" while using low tension rings which allow for excessive oil consumption at fairly low mileage.

Does everything comes inside the manual book you have ( torque specs) for the n14,n18 the hole engine? If so please share the name and where can I get the book Thanks

I think it would work fine. Better a bit more tolerance then to little. Look what happened to M539 resoration when he wanted the slight scuffed Block overhauled. (Complete Engine Failure after 200KM)

Get the opinion of the machine shop you will use to rebore it

Lovely job lad

If your going down that road and having a rebore it would pay to have the crankshaft machined and new oil pump

Hi George Have you ever rebuilt an E71 E72 BMW? My bottom end it’s gone and I need to rebuild it. Do you have any opinion on that?

I feel your pain and I think you’ve gone the right route. Tell me this though? Why have my VWs and BMWs used oil but my Citroens never have?

Hi George, thanks for the great content you post, I would rebore it for peace of mind, its out of tolerance, I'm not an engineer but have been around long enough to know its not worth the risk, Mark

I would say rebore and go with bigger pistons . But I’m no engine builder so I don’t know if that would through things out of wack regarding ecu mapping knock sensor etc . Probably your dad would be the best person to give opinion considering he has shop mate .

Well more money but it will be great in long run

Why not have a chat with Mark at Barum engines. He has a KZfaq channel & really knows his stuff.

I would speak to the engine shop first to get their opinion, and see where that takes you

Just rebore the block and fit bigger pistons. Otherwise it will still burn oil

My personal opinion.. if you like mini …rebuild it if you are sure the pistons will not fail you can put a little bit more boost in to the engine and make it even more powerful … I have R 52 cooper and I have so many ideas but obviously if you put too much boost in standard engine .. pistons not holding the torque ..I was thinking to put S engine and rebuild it slightly different than normal and different outlook engine section but my concern how the body of that little car gonna react with so many power 😂😂😂 I just love that car and if I have same dilemma I will do it ..

I would re bore them in that stripped down state George

You are so good with cars & I am sure u can fix it? I was gonna ask you if Mini was gonna be going up for Sale when sorted? Seems prev Owner didnt drive it carefully or might of had few few Owners that just can care or give it a service😜

Great channel. New subscriber.

Ahhh I have the same problem with my Cooper S engine (R56) I have measured the cylinders and three out of for are just in spec at 0.018mm oversize, however cylinder two appears oval as I have -0.05mm across the width of the block and +0.05mm towards the thrust side.........Do I also rebore to 0.25 or 0.5mm?????

I did a Triumph Stag V8 engine many years ago. When machining was not upto today's precision. They graded pistons to match the cylinder bores. The local Triumph specialist had stock of pistons and I bought the biggest standard piston he had. I took my block into work and honed the cylinders just to remove the lip at the top, and deglaze the cylinder walls. I don't suppose the same is possible these days. I did get some funny looks pushing a V8 block on a pallet into an aircraft factory.

Yep I’d rebore, ain’t worth messing with Plenty of good machinist’s about. I’ve had a couple of engines done , best way to go😎🤙🏽

Have you looked into getting those liners replaced?

If you want to retain your original pistons and original rings, can you not sleeve the block and have each cylinder machined out to 77.00mm?

Unlucky but Love it vids. Keep going mate. 👍

Can’t you re sleeve them or get larger pistons? And rings

Rebore and sell the pistons and rings you've already bought to recover some of the cost.

Barum Engines for your rebore They have a channel on here

rebore & new rings would be the way I would of gone with this problem

Can you get the block sleeved

How about having the block re-sleeved? Then you can use standard pistons and rings

That you are able to measure some ovality surely means there is wear there so the only way to return the engine to A1 condition is a rebore. Only other option is to swap the engine for a known good replacement really.

Just. Thought , seems as this is a cooper S ( turbocharged prince engine ) that Haynes manual actually stating that for a turbo unit or a N/A ? Ring gaps will differ between turbo and N/A

I would message the KZfaqr at barum engines he will know what steps to take.

I have the same BMW/PSA engine, after an engine mishap I'll spare the details mine required rebuilding, I was told by the company that's doing the work that the cylinders were fine and didn't need bored. But could find at the time piston that were OEM sizes instead they are 77.025 oversized strange I know. These pistons are forged like over parts of the internals. It's expensive however I will be keeping the car not sure if it adds profit to the car, I'd done it for the reliability. Would maybe something worth considering if you intend to keep the car and maybe looking for more power. Oil consumption is around 1 Ltr per 1000 miles roughly.

How can get that manual u have

Looks like an N14 engine? This is the reason why I avoid the R56. I have an R52 Cooper S and the Tritec is pretty much bulletproof, even if you pick up a car that’s been neglected

I've re assembled junkyard engines without honing and they run perfectly. You need to try it so that you learn and move on.

Rebore new pistons only way honing and fitting rings will extend the life of the engine but a rebore is the proper way no reason why it shouldn't do another 100k miles if the engine is done right

Pistons

I don't think it is that bad. You just need to get rings for the actual bore and not for the factory bore. As the oversize is consistent over all the four cylinders I suspect that the block has already been rebuilt once and in that process bored to 77.035. I doubt you would need oversized pistons to cope with that but definitely slightly oversized rings to accommodate your exact bore. Why would you want a block suitable for your new stock rings rather than rings suitable for your block?

Weired that the bores are that worn after 80K miles, I'd understand at 150-200K miles but 80K! Wonder if the engine was ran with poor quality or fuel diluted oil for a long period of time.

🙌🏼

Agree that's no good at all, it would only be worse than before. What are those bores made of?

Things like this should always be left for the professional 🤦‍♂️🤦‍♂️🤦‍♂️🤦‍♂️

new rings alone is half a job (especially with 80k on it ), re bore and pistons jobs a good un👌

Cant you put bigger pistols in?

Hi George, hope you don't mind me messaging again, have you watched barometer engines on KZfaq? Think they would sort your mini block rebore for you, just a thought Mark

I would of just rebuilt it if you are planning to tune it at all your going to need ring gap to play with if want to run big boost

Hi George, l would contact Barum Engines. They have a KZfaq channel and know what they are talking about. Defo need a rebore as 0.037 out round is too much.

Two schools of thought really! Dependant on cost of rebore and parts and what I expect from the engine once complete! After all the work and effort to dismantle and then rebuild the engine, if you go ahead without the rebore only to be disappointed with the finished job ie bad oil consumption, loss of power! Then it was all in vain! So I guess it’s best if you are in doubt, to bite the bullet and spend that money now whilst it’s at the current stage of work.

Have you considered having new cylinder liners fitted. A good machine shop should be able to press out the liners and fit new cylinder liners to original spec. Then it would be like a new engine. Ask about new liners at a good machine shop.

Have you spoken to Barum Engines?

Barum engins

I can see you are pissed off . Because you put a 110%in your work and want everything right . If you can source another engine thats 👌. And put your parts on it 😉 👍.

I think it’s fine! - just my guess not an expert-

Dose your father have access to a C,MM computer numerical measuring machine, to do your cylinder check for you,he must bein a quality position 😉 😀

First!

I think you should go ahead - it’s not going to matter. After a tenth of a mm it’s not significant. Can you even pinch your fingers to see a space that small. No

Yikes that is NOT a good hone job. You should always check your diameter min. and max. Dude let a true professional do your machining. You have no clue.

I can see you are pissed off . Because you put a 110%in your work and want everything right . If you can source another engine thats 👌. And put your parts on it 😉 👍.