Smoke under hard acceleration

[Defcon5]

I recently bought myself a shed, a £1500 '57 Vectra SRI 1.8vvt with 85k on the clock

Occasionally when accelerating hard, there is a blue smoke screen from the exhaust, which only appears to manifest itself between 3-5k rpm. It doesn't do it every time I use full throttle.

There are no lights on the dash, but a pedal test shows a stored code of P0170, which appears to relate to th MAF being goosed so wouldn't cause this

The previous owner saw fit to gererously overfill the oil during its last service (it's self serviced for the last 5 years) could excess oil be getting sucked up through a PCV system and entering the combustion chambers?

If it were piston rings/stem seals wouldn't it smoke all the time, rather than occasionally within a certain rev range?

It drives fine other than this, seems to be making full power and long term average mpg is 40.

Any ideas?

[FordPrefect56]

Blue smoke = oil burning.

3-5k = peak torque, peak cylinder pressures.

Most likely rings and bores. Do a compression test. Stem seals mainly manifest on initial throttle reapplication after a period on the overrun when the oil gets sucked down the guides.

[Defcon5]

Why would it only do it occasionally if it was the rings?

I've been quoted 600 quid to supply and fit a similar mileage engine, inc a timing belt change so if it's likely terminal I'll just do that rather than mess about with it (similar condition cars seem to go for about 2k so happy to do this)

[Inline__engine]

what likelihood would a compression test find oil control causing issue with the oil ring given that top and second ring do most compression sealing?
if there is significant bore wear the top and second ring seal will also be compromised so it could explains things but maybe not?

[bmwmike]

Provided the blue smoke is not too bad in light of the over filling I'd leave it a while and see if it clears.

How do the plugs look?

[Boosted LS1]

^ This. There may be excess oil somewhere in which case it may clear up after a while. Also, maybe check there isn't an oil leak onto the exhaust system. Are the tail pipes oiled up inside?

[steveo3002]

if its overfilled then sort that out , this may have caused oil to get into the breathers etc so pull those off and have a good look that its all dry

[Defcon5]

I've drained to oil to mid-dipstick.

I removed the dipstick with the engine running, there is a lot of suction down the tubes and it increased the revs. I tried to remove the oil filler cap but there is too much suction to do so. Could this point to a PCV issue? I seem to recall a colleague having similar issues on a similar age Astra

[Boosted LS1]

Nope, pcv could be working fine.

[HustleRussell]

Overfilling is the cause of the oil burning
Overfilling is probably also the cause of the MAF problem
Overfilling is bad.

[bmwmike]

Too much vacuum to lift the oil cap doesn't sound right to me but not familiar with this engine

[Garybee]

Sounds like pcv valve is stuck open. At idle it should be closed but will open as the revs rise/vacuum reduces. I'd remove the inlet to clean it out and replace the pcv valve.

[Defcon5]

One new rocker cover and it's good as new! There is a PCV valve built into it that had failed