Oil smoke... valve seals???

[miniblob]

Ok, so ongoing intermittent running issues with my M20 2.7 - having driven it in sunshine today, with clean windows, I can actually see some of the smoke coming from the exhaust.

Can ran perfectly for two 20 minute runs and a 30 minute run, quick splash and dash for petrol, started fine, but decided it's now idling about 1800rpm and running rough (misfire under full throttle, especially when on cam).
It's happened loads before, on & off - almost feels like there's something stuck in it's throat, (for want of a better explanation!).
Not too bad at light throttle, through town, but then onto a steep hill, misfiring a bit and down on power at full throttle (and when I release the throttle) I realised I'm leaving a big trail of blue oil smoke!!!
Back on the flat, I stopped to see what was coming from the exhaust at idle and there is some light oil smoke, along with a bit or burbling and the odd little pop. Def not running as it should.

Chances are, I'll start it up tonight and it'll be fine. It's just random when you turn the key, what engine/performance you're going to get this time - and how much oil it will use!!!
Pressed back into daily life, I'm topping up the oil a couple of times a week - probably 0.75L every few hundred miles!!!!!

Even when running well, (better), I do occasionally notice a puff of oil smoke when I lift off, normally after going through third gear above 3500rpm+, but not all the time!

So does this sound like an internal problem? Valve stem seals?
Worse?

My lack of knowledge means I really am guessing, but is this oil getting past a seal and sitting somewhere it shouldn't, until it's burnt off/seeped out?

Advice please!!!!!!

[martauto]

For the help I can be, the oil stem valve seals I have come across in the past blow smoke out when you re start the car after you stop for a while so maybe you could be looking at the piston rings ????
A compression check at this stage would help.

Mart.

[miniblob]

Hmmmm - I've had compression tests done and come back all ok (this was a while back, but the car hasn't really been run between then and a few weeks ago!)
It does seem to run rich too - oil is always black and smells of fuel - been that way since the engine was built.
It has been fully dyno mapped on a uni-chip ecu, but never really been convinced it's running 100%.

It's been running a lot better the last week or so, albeit still with a fussy idle! More often than not it'll bounce between 1000ish and 6/700 ish nearly stalling, but sometimes it's fine and sometimes it decides it's gonna sit at 13/1400, or anywhere really!

Seem to just be constantly going round in circles, checking and re-checking the same things on this car - I want to get it sorted!

[miniblob]

It's going in for a Cambelt change, rocker gasket and check valve clearances and a few other bits on Monday, so I can get the to do a compression test again.
What figures would be expected on a heavily modded M20?

[miniblob]

Ok, this hasn't changed like I was expecting.
I'm a bit concerned now!

Idling at around 1750 ish (once warm) and leaving a lot of oil smoke under throttle - especially when it tries to come 'on cam' - def down on power.

Topped it up and the oil level light came back on, needed another .75L after 50 miles!!!

I'll get them to do a compression test tomorrow - can anyone help with what figures to expect???
Any other suggestions???

Really don't want to be doing an engine rebuild now - not got the budget for that!!!!!

[BenHar]

It sounds to me as though you have more than one problem.

Idling is likely to be air leaks on the intake.

Smoke could be knackered or gummed up oil rings. This might be why you have fuel in the oil, too.

Ben

[miniblob]

Hmmmmm, literally been through everything for airleaks to get this sorted in the last two weeks!!!

When you say oil rings........ do you mean valve seals or piston rings, or something else???

[boiliebasher]

Hmmmmm, literally been through everything for airleaks to get this sorted in the last two weeks!!!

When you say oil rings........ do you mean valve seals or piston rings, or something else???

I believe he means piston oil rings mate

[miniblob]

That's my biggest concern at the moment.

Compression test will be done today!

[boiliebasher]

That's my biggest concern at the moment.

Compression test will be done today!

Compression test won't necessarily determine the condition of the oil scraper rings. It will however give you an indication of the cylinder bores and piston rings

[miniblob]

Yep, compression test confirms my fears.......... it's dead!

Cyl 1 - 0
Cyl 2 - 105
Cyl 3 - 87
Cyl 4 - 89
Cyl 5 - 72
Cyl 6 - 103

Severe oil contamination on plugs!!!

Will do a separate thread with thoughts about builds/re-builds/etc.

Bugger. Merry Christmas!!!

[boiliebasher]

Oh dear, sorry to hear that mate!

[martauto]

Oh dear, sorry to hear that mate!

Shit !!!

Mart.