oil in one cylinder

[Alan L]

So I think I posted this earlier in the 930 forum but will try again here.
My 930 started burping oil out of #1 cylinder - fouling the plug and leaking out of the header. I suspected maybe broken rings. But the leakdowns were 2% across all 6. The P&Cs are about 30 hrs run time from new. I triple checked #1 cyl over a couple of days. Those are cold numbers.
Finally I pulled the engine down and removed #1 P&C. I could find nothing wrong. The bore is mint and no obvious issue with the piston or rings. I pulled the valves and again no obvious issue. I replaced the seals while I was at it. Boxed everything back together and finally ran it again today. Same result - oil burping from #1 header. I will pull it down again - prob tomorrow.
But what should i be looking for? I have obviously missed somethiung somewhere.
Thanks
Alan

[john walker's workshop]

Worn guides?

[Alan L]

I will check more closely this time. I was in a rush trying to get to a road trip of track meetings.
It seemed to happen when I was having dizzy problems - so suspected timing issues/rings. There had been no sign of oil previously - ie last few weeks of meetings. More like a failure than wear.
The guides were well in spec 30 hrs ago, but I will check.
I have more time this time round.
Thanks for the reply - I am at a bit of a loss here.
Regards
Alan

[stownsen914]

How long did it sit? Oil level can rise in the sump as oil level equilibrates with the tank after sitting for an extended period. Perhaps as the oil level rises just past the bottom of the cylinders, the ring gaps in that cyl. line up to promote oil getting past the rings?

[Alan L]

I had just reassembled it - half hr after filling with oil.
When I pulled the piston I re set the rings - so there were no gaps at the bottom.
Just looking for ideas for when I pull it again. Need to find something that is the culprit. Must have missed something.
Hopefully I will have that piston out again today and maybe a closer inspection will tell me something.
Thanks
Alan

[stownsen914]

Could oil be finding its way into #1 through the intake somehow? There would be evidence of this, if it were the case.

[Alan L]

Yes - possible. It is a head scratcher right now - I did pull the valves and saw nothing weird. Guides seemed firmly seated, replaced the seals - just in case.
I have to pay more attention this time round.


You can see the wet spot next to the valve guide.


It has to be coming past the piston, or thru the head - right?
There are no other options?
Thanks
Alan

[stownsen914]

Since it fills quickly, it may be possible to tell with a borescope what the source is

[gled49]

So I’ll ask the dumb question. Was the piston direction toward flywheel followed. And what displacement is the engine.

[Alan L]

Yep - the mark is to the flywheel. I will be able to show you a pic of that soon, when I pull the head.
So this time I have noticed a pool of oil behind the inlet valve. That has to be a clue right?
Does that eliminate piston/ring issues?
Didn't see it last time - but the valve may have been open. Luckily it was shut this time.
Alan

[rowingone]

you've replaced the valve guide . . maybe its the valve itself?

[john walker's workshop]

Mic the valve stem top to bottom. I replaced a set of intake valves recently that measured 8.96mm at the top and 8.86 at the bottom. Lots of carbon buildup on the valve seats, exhaust ports and piston tops. What type of stem seal? White or brown?

[Alan L]

Brown valve seal. These heads have been on about 30 hrs+ . I would have put new seals on at that time. I replaced the seals this time round - again with brown.
The heads were not new - but measured well in spec as far as the valves/guides went.
Yes - I better start measuring stuff this time round. Was looking for something damaged/broken last time.
I may have some green seals somewhere.
Thanks
Alan

[john walker's workshop]

Brown are hard to get on straight. If they are angled, there's a gap. Been using white teflon forever.

[Alan L]

Hmm - OK - thanks John. I will have to have a close look.
The puzzle is that this happened suddenly - after having green wire/dizzy issues. Suddenly dropped a cylinder and a puddle of oil under the header.
I put a snug socket over the valve seal - on the shoulder and tap them down til fully seated. I will have to check how straight they are. Thanks.
I had vaguely hoped I could pull the head without splitting the trans out - took me near 50% of my time last time to mate it up. But that plan won't work - the headers will kill me. Wondered how far I could get, but near hitting the wall now.


Grand daughter just turned up - car making a noise. Going to get a bit distracted - hopefully not for long.
Thanks
Alan

[Alan L]

OK - the valves measure 8.96 top and bottom for I and 8.94 top and bottom for E.
You can see from the other pic the piston mark is facing #2 cyl/flywheel.
The guides seals - newly fitted, seem straight.
I am not kicking myself so much now for closing it up last time. Nothing obvious going on here - that I can see. But the amount of oil getting into the cyl is more than slight. After about 2 min of idling yday, about a teaspoon on the floor from the header. That will not be counting what went out the exhaust - just what leaked past the slip joints on the header.
Where to next?
I guess I should check the guides for tightness - in the head and clearance on the valves.
There are no marks inside the guides.
Can't remember the quick check for guide/valve clearance. Dial gauge against the stem etc - but don't recall the details. Sent the heads out for checking last time before installing.
Thanks
Alan

[Alan L]

You can see a small pool of oil sitting in the bottom of the cylinder in the piston pic. Then there was the oil sitting behind the Inlet valve. So I figured if the valves were dribbling that much I should be able to replicate it. Put the valves in and dribbled oil on to the top lip of the seal and kept it wet - a drop or two every 10-20 secs (it dribbled off). After about 5 mins , checked below to see if any had come down the stems. Nope.
Alan

[Alan L]

Wondering if a guide is coming loose. Seemed to happen suddenly - this is not a gradual thing.
But it happens from stone cold - within a couple of minutes I have oil on the floor.
May try heating the head in the oven (while wife not looking) and see if guide is loose. They look OK right now. I did pull the 1-3 headers off before dropping the engine first time. Fired it up and watched from below. had oil splattering out on to the floor (and me) and was watching the guide. Didn't move - but that was only the E guide.
Alan

[john walker's workshop]

Did you pull that cylinder off yet? It's a turbo and turbos break rings.

[Alan L]

I pulled the cylinder last time I pulled it down - like a couple of weeks ago. Could not find anything. Pulled the piston. And the leakdowns are good. So I put it all back together - hoping to make some race meetings I had signed up for - big road trip. Fired it up - and oil again. Rings were my first thought after the timing issues. Thinking of pulling the piston once again - since I am this far in. But I actually reset the ring orientations last time as I put it back together. Yes, I was in a hurry - trying to meet a deadline - ferry bookings, accom, meeting entries etc. $000s . But I am sure I would have noticed the broken rings. Was a relief not to find any. So I closed it up again - hoping.
Still thinking a loose guide would be needed for this amount of oil?
Thanks
Alan