valve stem seals, head gasket or a new M20B25 crack?

[gareth]

after a recent engine flooding non starting episode, my M20B25 has started burning LARGE amounts of oil on startup and seems to be running on 5 cylinders. it clears its throat when booted but the problem is obviously still present.

i suspect the following could be the cause:
1) valve stem seals are the common cause for smokey startup but these were changed when i rebuilt the replacement head in january.
2) head gasket gone between an oilway and one cylinder (no oil in water / water in oil apparent so far)
3) a crack in the head in either one of the ports or the cumbustion chamber allowing oil to seep in there while stationary.

i'm totally stumped as to the case of this as the above ideas seem unlikely. any ideas? it was running fine (if a little spluttery when cold) before it flooded...

[dasparkybad]

is it definatley oil blue smoke or black
if it is black tthen your problem is overfuelling on start up
this can be caused by the engine temp sensor being faulty

[gareth]

engine temp sensor is new. anyway it's definately oil.

i wonder if it's doing something odd with the breathers?

[kirils]

could it be a broken piston ring?

[gareth]

i suspect it might be. i took it out earlier and there's now a knocking noise from the bottom end....

M30 time is approaching!

[Andy335Touring]

Have you done a compression test ?

Have you took all the plugs out to see if one is oily ?

[gareth]

i've not had a chance yet. unfortunately i had a fully booked weekend and don't really get the oppertunity to fiddle with the car in the eves.

strangely, the amount of oil it's burning has reduced but the engine doesn't sound happy. not too loud but i'm sure there's something there. it's a bit hard to tell with the scorpion exhaust and a fairly tired cam...

i'll have to just have to see what symptoms appear and do the obvious fouled plug & compression tests as you suggested at the weekend.