burning oil - reason yet undiscovered - suggestions please

[red baron]

Hey guys,
I have an engine with the following specs:

- 90.5 Mahle pistons with Total Seal third ring
- Engle W125
- 1:1.25 Rockers with swivel feet adjusters
- DRD L5 heads with stainless steel valves
- CSP crankcase breather box (big one)
- CSP valve covers with breather outlets
- 44 IDF

The problem occured is, that I discovered oil at the exhaust flange between head and header on cylinder 3. After disassembling and cleaning oil appeared there again and the engine had some blue smoke. Also the spark plugs looked quite oily. It was not exessivly blue smoke but recognizeable. It got worse over time until cylinder 3 didn't fire anymore - just sometimes while pulling the spark cable slowly away from the distributor.

So I disassembled the engine and found good looking pistons and cylinders with recognizable combustion residuals in the area of the piston to end of barrel (1.5mm). There is was recognizable that there must have been oil sitting at the bottom, since it was not oiled there. This doesn't give me too much pain.

Checking the cylinder heads, there is nothing super frightening but the valves and valve guides do look a little bit odd. I have some pictures here:

BTW the engine was until now not running more than 200km.













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The valves have visual wear but are round and not criticaly below 8mm. The guides are not ellipsed - but a bit widened in the middle of the guide lenght: About 0,05mm maximum. Also when I'm pulling out the valves you can feel a edge at the end of the stem just before the spring retainer grooves start. I really have to pull the valve out with more force than usual

I contacted a guy being expert in rebuilding cylinder heads and with his equipment we measured that all the valves seal properly and that the guide is 8mm and not more. His opinion was that if he would replace the guides he would do them bigger than 8mm diameter.

What also caught my eye is that the oil ring seems not to be exactly stiff but measuring is about impossible. The first rings have a gap of 0,5mm to 0,55mm. The second (total seal) have about 0,55mm to 0,65mm and at one cylinders the gap of thick and thin second ring was at the same position.


Questions:

What do you think about the valves and guides? My impression is that the valves are of poor quality and that something might be wrong.

How can I check if the third ring is fine? Any problems known with the total seal ones?

Any problems known with the CSP breather boxes that they do not efficienly separate oil from air?


Thank you so much in advance! Any suggestions are appreciated!

[Lids]

Oil can only get in the combustion chamber via the valve guides or the rings.  I presume the breathing system is open to the atmosphere via a filter. Is the smoke worse at start up

[BeetleBug]

Oil can only get in the combustion chamber via the valve guides or the rings.  I presume the breathing system is open to the atmosphere via a filter. Is the smoke worse at start up

x 2. A leak down test would have give you all the answers but now it is too late since you have taken the engine apart. A leak down tool is not much money either and the test take approx 15 minutes with the engine out and a little longer with the engine in the car.

My guess is the rings and looking at your breather box perhaps also the breathing system.

Best rgs
BB

[wph]

Take your piston ring packs and check the oil ring expanders. I have witnessed several
broken tabs on Mahle expander ring ends, if the other one is broken you have no tension
what so ever on the oil control rings.

Pekka 

[spanners]

Take your piston ring packs and check the oil ring expanders. I have witnessed several
broken tabs on Mahle expander ring ends, if the other one is broken you have no tension
what so ever on the oil control rings.

Pekka 

^^^^^*^^^^ this, it can also damage the land if run long and hard like it, eyeball the oil ring land carefully.
Another possibility is a heavy ported intake port may have broken through into the rocker chamber, oil gets sucked into the cylinder big time.

[red baron]

Hey guys,
thanks alot for your thoughts. I had the rings out and none were damaged. Just gave me the impression of having not enough tension to press then on the liner wall.

The breathing system is connected to the valve covers and filler neck with the lower tubes and the upper ones are going to my air filter. The carburators do not show any sign of oil coming there in a big amount.
Considering braeckthroughs of the ports: I did a leak test on all the valves and there were all fine. Carried out with a vacuum pump placed on either the exhaust or inlet flanges of the heads.

What are your thoughts about the valves after such a short time running the engine?

[wph]

Broken tab on the expander is way too easy to miss.
I couldn't find an actual photo of the said tab but a drawing instead.

   

It's almost physically impossible to install expander incorrectly but If either of the tips is broken you'll have an oil burner

I really have to pull the valve out with more force than usual

Always use a fine lapping stone or diamond to deburr valve lock grooves before pulling the valves,
otherwise you'll damage guide bore which may also cause oil consumption.
In a worst case it's like reaming the guide to an oversize.

Pekka