oil problem

[morrisman 54]

Hi,
The rings were put on to the pistons by my engineer,however today i've took it down the road warmed it up and tried the rocker cover cap test and it was fine,no smoke or fumes,so i chanced it to go in to town and back and it was ok and hasn't used any oil at all?? There was a slight puff of smoke coming back for about 10 seconds and that was all,very strange indeed.
Not sure what to do now,maybe just drive and see what happens......what do you think guys?
regards Andy

[David53]

I would be checking your compression - that would soon tell you if you have broken a ring or two

[bmcecosse]

Indeed - drive and see.......

[kennatt]

wasn't just overfilled with oil was it,different dip stick or something like that

[IslipMinor]

Maybe 2 problems:

Clouds of smoke after a short distance from a cold start

Excessive oil consumption

New guides - are they phosphor bronze or the standard cast iron? If they are PB, it is possible that they are 'nipping' the exhaust valve(s) during the warm up phase and causing the smoke. Do you get a misfire at the same time as the exhaust smoke? Also do you have the by-pass water hose fitted? Shades of a problem I had a few years ago! The 'nipping' is caused by local overheating and can settle down as the guides are broken in during the 'running in' process. Do you have valve stem oil seals on the exhaust valves? Must be fitted to the inlets, but not to the exhaust valves - they need all the lubrication they can get!

Excessive oil consumption - broken rings will allow oil up into the combustion chamber and also create crankcase pressure and leaks. What oil filler cap are you using - it must be the vented type. The timing cover vent has to be connected either to the carburettor(s), if there is a connection, or to the inlet manifold PCV (if fitted). It should not be allowed to vent to atmosphere - the secret to keeping the oil in an A-Series engine is to have a slightly negative crankcase pressure. The early non-vented type will cause severe problems and oil leaks on the 1275 engine - it is designed for negative crankcase pressure, the same as any modern engine is.

[morrisman 54]

Hi everyone,
Just another update,have been down the road again and it started to smoke again but not very much. In answer to your ideas,i don't have any misfires,yes i have the bypass hose fitted and also fitted stem seals to inlets and exhaust valves. i'm planning to get the mini people down at southam to take a look as this is getting very confusing! It may just need a good run who knows!

Andy[frame][/frame]

[bmcecosse]

I don't have your confidence in 'the Mini people' - the advice about the timing case breather was very wrong..... And a good 1275 engine should NOT have stem seals on the exhaust valves. I suggest a compression test will be well worth doing. And honestly - I would pull the pistons to inspect the rings in case they are broken - and damaging the bores and the pistons.

[morrisman 54]

Why no confidence in those guys?.......regarding the other matter i'm afraid i've put stem seals on all the valves,what
harm will that do if anything?
regards Andy[frame][/frame]

[bmcecosse]

High performance engine needs a bit of oil down the exhaust guides.

[morrisman 54]

Have decided to bite the bullet and strip the engine down, as everything points to pistons or rings so might as well do it
right first time,was smokin bad again today so will keep you all posted,thanks again for everyone's advice as it's always good
to hear opinions from the technical wizards!
regards Andy[frame][/frame]

[bmcecosse]

At least with an in-line engine it's relatively simple to pop the pistons -much more of a job on a Mini!

[les]

Glad to read you're checking the pistons, when you said a couple were hard to get in, I found it hard to believe you left it at that. I'd have pulled them out again to find out why. Your engineer may not have gapped the rings-- you're too trusting!

[morrisman 54]

Evening everyone,
Well i've checked pistons and rings and all seems to be ok,no damaged or broken rings,so something is causing the
pressure in the crankcase but not sure where to go from here. I really want to get this sorted soon as i'm off to the moggy
national rally at the end of june.
Andy[frame][/frame]

[bmcecosse]

You just need to confirm the bore size against what it should be - and double check ring gaps. And are the rings fitted right-way-up? It's then down to providing sufficient crankcase breathing - from the timing case cover and from the rocker cover. And run them into the carb - or directly in to the inlet manifold, although this should not be necessary on a 'new' engine. Also need to consider valve guide/valve stem clearance - my own view is this has little effect, but others seem to place great emphasis on it.

[les]

I don't know if you've fitted new pistons but if not Is it possible that the ring grooves are worn? This could give a 'pumping' effect.

[morrisman 54]

Went to see the experts today,it looks as though the pistons are a little tight at the bottom of the bores and the rings
don't seem to be gapped to well! Will know more when Rod and Colin from the mini metro centre have measured it up
properly......whatever happens don't think it will be a cheap fix. Will keep you all posted.
regards all Andy[frame][/frame]

[les]

Pistons are probably right at the bottom, rather than tight, and loose at the top, (thats how bores wear), sounds like the tightness is being caused by no ring gap when at the bottom. From what you say looks like the bores are not parallel and need reboring, not sure you can safely go more than 60thou though. Change your engineer!

[bmcecosse]

+ 1 on that....