Slight blue smoke rom rear after long lay up

[NickVR6]

As per the title, I have just managed to change the cambelt (and water pump etc), and started the car for the first time after the previous owner stored it for several years.

Blue-ish smoke from the silencer.

So this could be valve stem seals, or piston rings. Any idea how to differentiate?

And if it turns out to be piston rings, does anyone know if they can be changed from below without removing the head?

P.S. one recent post here remarked in the difficulty of changing the cambelt due to access. The picture attached is of a clever 'stubby allen key with a 12 mm hexagon head' with an extra long 12mm ring spanner with ratchet option. Absolutely invaluable in undoing and doing the socket caphead bolts.

Oops can't see how to easily attach a picture. I will research this and update this post but the description should be enough.

[Scotelan]

As per the title, I have just managed to change the cambelt (and water pump etc), and started the car for the first time after the previous owner stored it for several years.

Blue-ish smoke from the silencer.

So this could be valve stem seals, or piston rings. Any idea how to differentiate?

And if it turns out to be piston rings, does anyone know if they can be changed from below without removing the head?

P.S. one recent post here remarked in the difficulty of changing the cambelt due to access. The picture attached is of a clever 'stubby allen key with a 12 mm hexagon head' with an extra long 12mm ring spanner with ratchet option. Absolutely invaluable in undoing and doing the socket caphead bolts.

Oops can't see how to easily attach a picture. I will research this and update this post but the description should be enough.

Worn/hard alve stem seals will show smoke after the overrun due to the high vacuum drawing oil past the seals on closed throttle. Bore glazing or wearing is generally constantly burning oil. Hope this helps

[dapinky]

The method I use for testing rings is to do a 'dry' compression test, note the 4 numbers, then add a small squirt of engine oil into the cylinder from the sparkplug hole and do it again.....

... if the numbers are the same, then the rings are usually fine, but if there is a significant increase in the compression (the oil film will form a temporary seal) then there may be wear in the bore/rings.

I don't really know what would be considered a 'significant' increase in terms of numbers, but you are looking for equality across all 4 pistons.

Removal of the pistons can be done from the bottom, but as it requires removal of the crank (so detaching it from the clutch/gearbox), which means removal of the gearbox, I would consider it far easier to do from the top. Obviously, if you choose to remove the whole engine/gearbox assembly from the car it may be viable, but otherwise I'd take the head off, remove the sump and leave the major units in situ.

Removal of the head will be necessary to replace the stem seals anyway, so if you think the rings are worn, it may well be worthwhile swapping the seals at the same time.

It may well be that if the car has been standing, the rubber seals will have 'set' a bit, or the bores have glazed a bit, and it all clear up with a bit of use..... only time will tell.