Blue smoke. please help! lol

[chris H]

Ok guys so the engine was built 1300 miles ago to standard spec, new rings and rehone, valve stem seals, oil and water pump and gaskets, now the car runs great, ticks over a little quick but still runs good.

if i back off the throttle from example 70-80mph and let the car roll down to say 60 as soon as i touch the throttle again there's a plume of blue smoke from the exhaust (quite a bit of smoke), it lasts about 4-5 seconds and clears up till i do it again.

I thought it was the turbo but i've changed it 3 times and it still smokes exactly the same.

Today i ran a compression test from cold and got

165 psi on cyl 1

175 on cyl 2

180 on cyl 3 and

180 on cyl 4.

I did cylinder 1 again with a couple of drops of oil down the plug hole and got 180 psi.

I removed the cylinder head, checked the bores and they look fine, no scratches and i can still see the cross hatching from when the block was honed, only thing i can think of is that i haven't clocked the piston rings on cylinder 1 when i put it together.

Gonna take the pistons and rods out tomorrow and have a look.

anyone care to take a stab at what's up with it? lol.

Any ideas are welcome..

Cheers,

chris.

[crouchy]

are u runnin a oil catch can if so it needs a breether for it cause my mate had a simaler problem hope this helps cause there nohin worse than strippin an engine down for no reason

[chris H]

No mate, not got a catch can but then the breather pipes are venting to atmosphere anyway so it's deffo not that.

[crouchy]

hows your pcv valve cause that causes smoke

[Lawsy]

Sounds abit like valve stem seals to me, on over run the throttle plate will obviously be shut, causing the the engine to have almost complete vacuum, so the engine will have alot of negative pressure. So if your stem seals are worn or are not a great seal, on overun (backing off) the engine will suck oil from the cylinder head through the stem seals. Then when you put your foot down again you will be burning off the oil in the cumbustion chamber.

Just a thought, but might be worth while?

Stew

[chris H]

Lawsy, that's exactly what i was thinking mate, gonna pull the pistons out this afternoon and check them over just for peace of mind but it's doing my head in lol

[chris H]

Just quickly, i'm on as we speak checking the pistons over and there's no signs of blowby on the pistons.

Can someone tell me what the maximum piston ring gap can be? I've took the rings off the piston and put it in the bore. tested the gap and it's 0.55mm. sounds ok to me but can someone confirm?

cheers

chris

[chris H]

This was on the magnetic sump plug

Piston. no scratches on skirts or evidence of blowby

piston ring gap 0.55mm (gap is at 12 o'clock)

what say you??

lol

there is a literal drop of oil on two of the intake valves so looks like the injectors were spraying fuel on to them and washing the oil off and into the combustion chamber hence the blue smoke.

The cars used about 2 litres of oil in 700 miles!!