Rebored Engine burning Oil

[Minornut59]

Hi.
Hope somebody can offer advice.
Its not Minor related although its an A seeries engine.
To be more precise its a 1275 engine from an Austin 1300 that ive put in my mini.

the engine was worn so i stripped it, had it rebored to +20 thou and used some old but good +20 pistons i had. When i came to order rings for them i had problems getting them from the Mini specialists as they are 4 ring ones (3 comp and 1 oil)
and all the new ones are 3 ring.
So i asked the buy doing my block rebore to see if he coul get some rings and gave him the pistons for reference.

He managed to get some new old stock ones ok, but they were Cords rings, the ones that were made up of lots of thin rings and were the ones people fitted to worn engines to keep them going.

He said these would be OK. Now ive been using this chap for my machining for years and generally i trust him to know what he's talking about.
Having built the engine and fitted it i was dismayed to find its literally chucking out clouds of oil smoke. So much so, that driving the car leaves a smokescreen behind it.
I have running in oil in the engine.

I did a compression test this morning, having covered only 100 miles since the rebuild and all four pots are holding 11 bar compression, with a wet test this goes up to between 13 and 14.5 depending on the cylinder.

I would have said 11 was good, but the fact the readings have gone up suggests the rings are not doing their job.

An experienced mini racer and engine builder of my acquaintence tells me the Cords rings are no good and will quickly wear out my new bores and that i should get a set of 'proper' rings. He recommends Hastings in the USA.


Cords rings say online that their rings shoul be ok in new engines..

The mini is obviouisly unhaapy and i'm not using it until i decide what to do.
Someone else suggested draining out the running in oil and just sticking 20w50 straight in and seeing what that does.

I've rebuilt a few engiones in my years and have always used running in oil to bed them in and have always had an oil tight engine almost straight away with no blue smoke..

Thoughts please....

[bmcecosse]

I definitely would NOT have used Cords rings in a rebored engine.... It's also VERY important that Cords are installed right way round - otherwise they can pump oil up into the combustion chamber - rather than holding it down in the sump/gearbox. How is the crankcase breathing arranged? Is it connected to the intake system in some way to ensure there is no internal pressure?

[Minornut59]

The mini has two breathers; one on the crankcase at th flywheel clutch end, and one on the rocker cover. the rocker cover is fed into the air filter housng and the other one is open to atmosphere with a small k and n type filter on it.

I took care to install the rings the correct way around following the instructions etc

[bmcecosse]

Well done getting the Cords right way round. If you rev up the hot engine with the oil filler cap removed - is there a plume of fume/smoke ? Were the bores honed (usually a cross hatch pattern) after the boring? Any reason to think the bore size may not be correct? Maybe it will settle down.... What grade is the oil??

[grumpydad]

Hi
the Op has 160 psi compression
thats quite good
I have fitted cord rings on new reboard and rerung pistions
on 3 motors 1275 with no problems at all

I would be looking at the valve stem seals

[Minornut59]

hi BMC,

I'll check the engine with the cap removed tonight when I get home.

I've never honed the bore after a rebore; never needed to, but the bores were not glazed; nice and dull.

running in oil is in as I said, which is really thin.

Going to speak to the engineer to ask him to check the sizes he ordered and the bore size he did. He keeps records like that.

Not sure if it will settle down like it is; its horrendous the amount of smoke it emits.
Wondered if refilling with 20w50 would help it stop burning. but then it may not run in?
Someone else said it may not anyway as Cords rings are harder than normal.

Also going to see if I can ascertain if the dipstick is reading correctly. Has it got too much in?? Don't think so, but you never know.

Grumpydad, thanks. Brand new stem seals on the head, which was rebuilt some years ago with new guides etc. I just removed the valves after a period of inactivity, (head was in my shed after I removed it from another car of mine some time ago, cleaned everything, ground them in, then fitted new seals on all valves.

[bmcecosse]

Valve stems only give a puff of smoke after an over-run. I have never used thin 'running in' oil ....

[Minornut59]

Think I'm going to get home tonight, drain off the running in oil and stick some 20W 50 in with a new filter and then go drive it. Perhaps give it about 50 miles and see whats what after that

[bmcecosse]

Good plan I think.

[Minornut59]

OK, i drained the running in oil and refilled with 20w50 and have covered about 70 odd miles plus so now the engine has done 200 miles since rebuild.

The engine is using less oil; ie less of a smokescreen but its still burning it, so much so that every trip means your clothes end up stinking of oil smoke, You can see the oil smoke clouds when you rev it.

Removing the rocker cover with the engine running and hot you get a tiny puff of gas there but nothing much at all.

Interestingly, when i drained the oil out it would hardly flow UNTIL i removed the rocker cover, then it ran out normally.
This would suggest blocked breathers, yet the crankcase breather on the bellhousing is clear, ( i removed it and blew it through- it was fine) and the one on the rocker cover that goes to the air filer is also clear. The air filter is new and still clean and the housing was washed out anyway.

Am stumped....

Showed the engineers at the garage who did the boring and supplied th ring and they saif carry on driving for a bit and hope it settles down but my feeling is it won't.

Any more ideas?

[Minornut59]

I meant remove the oil filler cap on the rocker cover, not the rocker cover itself.

[Minornut59]

Ok, further to the last posts.

I have just removed all four plugs with the engine hot. All are normal in colour; ie. light grey/brown in the middle. Some black around the outer edge where the threads go. But they appear quite normal to me.

I have also taken off the crank breather and re-checked it and its clear. I also have stuck my airline into the breather and blown in compressed air and i could feel this coming out of the open rocker cover/filler cap. Whether or not there was a blockage in there, there isn't now.

Car still smoking but i am now wondering if some of it is the oil IN the exhaust that is burning off....??
I will have to monitor the oil consumption and see if its still losing any.

[bmcecosse]

It could well be - a good hard run away from populated areas may be needed....

[Minornut59]

Well, i have sort of been doing that already with little improvement so far and the oil HAS gone down...

But, do you think it could still be the rings given what ive said?

[biomed32uk]

I have to admit that I have always been taught, told and read that when ever you disturb the rings for whatever reason or fit new ones then you need to at the very least break the glaze in the bores with quick scuff with some emery. Its never stood me wrong with any engine.

I have just rebuilt my engine, the bores were fine and I fitted new rings. I gave each bore a few runs up and down with a honing tool. a nice crosshatch pattern showing.

Engine rebuilt, using Millers running in oil at the moment and I am getting no smoke at all, other than the initial start up.

I really do think you have a problem with rings, they may just bed down after a while but it will be a long while. Really need to come out and de glaze the bores.

[philthehill]

What was the piston ring to piston clearance?
If you fitted new rings to old pistons the clearance above (or below) the ring could be excessive and oil could be pumping past the inside of the rings due to the rings moving up and down in the piston grove.
I agree that the bores should be de-glazed every time before fitting new rings unless of course you have nice new bores - but a nice cross hatch does help with running/bedding in even in new bores.

[bmcecosse]

The Cords rings are specifically designed to cope with slightly worn piston grooves. The compressions are good - I would be investigating the installation of the oil rings for 'right way round'... I know you say you took care, but....

[kennatt]

yes, hone the bores with new rings but this engine has been rebored so shouldn't need it,the rings should bed into the already prepared bores as a result of the rebore., I wonder if one of the oil control rings,,has been damaged on assembly,easily done.Mind you would think that it would show up on the plug,if its that bad.can't remember what the cord oil control rings look like,its been a long while but aren't they just two plain rings each side of a corrugated scraper,so can they be put in upside down

[bmcecosse]

Yes - the sprung rings are tapered and each has to be put in right way up. They are 'tested' by flexing in the fingers... The newly bored cylinders may not have been the smoothest surface - and certainly on competition engines, the boring would be followed up with cross hatch honing.

[Minornut59]

Yes, thats my suspicion.
Have to say i will hone the bores with an engine if i re-ring it and it hasn't been rebored but i have never bothered to hone the bores with an engine ive had bored out and ive never had this sort of problem before. After the initial running in oil the engines have usually been oil smoke free for years.

Ive just eliminated all the oil from the exhaust pipe, having removed the pipe and burnt off the oil inside. After 15 mins the flames died down.......so there was quite a lot of oil in there i think.