Ok whare do i start.i got a sapph cuple of years ago,stage 3 t34 greens 3bar map sensor, and from day one i noticed it smoked right bad wen going down a hill,in gear with no throttle (no smoke) and then re-aplyn throttle it smokes like mad for few secs then clears.other than that its perfect.no smoke any other time.i re-built the full bottom end last year due to a bit of a mis-hap! it got re-bored,0.5 oversized pistons,acl bearings bla bla.so i thot wotever the smoke problem was it wld av been sorted. wrong! during run in period i noticed it was still doing it.exact same! no better and no worse! i used genuine ford valve stem seals on the head aswell. now,wen iv been looking into this i have heard more than one person say it cld be valve guides worn! but how can oil pass stem seals only when it does? (re aplyn throttle going down hill) PLZ HELP!!! O,the turbos been done Twice by CR turbos so its not that.and the breather systems doesnt seem to b blocked. cld overfueling cause this??? any help wld b very very much appriciated, thanx Richie...

 

What you are seeing is smoke on overrun, also defo valve guides a notorious weak point on the engines! When on overrun the vacuum created will draw the oil through the worn valve guides and into the cylinder, when you open the throttle again this is burnt and sent out the exhaust.

Martin

 

Do you have a centre box in your exhaust?

 

As said defo guide wear, they are usually shagged when they have around 40,000 miles on them, if you get new guides get COLSHIBO, much much more expensive but last, vastly better than the rubbish fitted as std.
tabetha

 

thanx alot guys. i was expecting that answer but as i mentioned i wasnt sure. aw well at least iv got time b4 it gets set up in summer and also,wot head gasket do yall recomend? i put a multi layer steel victor reinz wrs number on it wen i built it but have been told the group A gaskets are number 1 choice.. thanx again

 

Unless running well over 500bhp I would use a YB 0611, group a gasket.
tabetha

 

Mine does this, but it has brand new bronze guides in it, shitty stem seals?

 

mine does it a bit too,just rebuilt engine

 

i put decent seals in

 

all cossies smoke a bit, i just dont look in my mirror, that seems to fix it!

 

mine used to smoke and it ended up being the metal gauze filter in the breather pipe - removed that and job done - but mine only did on hi boost on throttle so a bit different to all yours

 

i think some of it comes from the turbo seal.I had a bend in the oil drain pipe that was a bit sharp.i put the standard one back on and it has nearly stopped it from smoking.I'm also wondering if the turbo feed pipe union is to big,therfore letting to much oil into the turbo,as i have put a high pressure pump on the engine.

 

Another theory i have is to put a vacum on the crankcase breather,as at the moment its just vented to air,the usual bailey style.If i had negative pressure in the crankcase,it would help pull the oil out of the turbo drain pipe

 

The reason why oil gets past the turbo seals is because it doesn't have any!!
You can get the step gap modded, the seal as such is simply a ring like a tiny piston ring, complete with a gap between the ends to let oil through, but a step gap seal sorts 90% of this.
Bronze is ok, better than std, but COLSHIBO is expensive for a reason, all my oil's going past the shagged rings!!
tabetha

 

is oil leaking past a common problem,my turbo has only done about 1000 miles,what size should the union hole be .I bought a new one from burtons and it was about 2mm bigger than the one i had.

 

must admit it does bug me

 

A certain amount of oil will get past as when not on boost there is a vacuum in the inlet then, a step gap seal as said sorts about 90% of this.
I don't know about the union size hole, but the pressure will be the same so shouldn't make any difference.
The negative pressure thing you mention is interesting, some cars in the us ran with evacuusump, where they had the sump connected to the exhaust, in between each positive pulse in the exhaust there is a vacuum pulse so exploited this, with anti backfire valves in the exhaust so a back fire didn't blow the sump off!!
tabetha

 

as said above, check breather system, also, daft as it seems, you using correct oil? i was leaving mine stood for 3 weeks at a time(while working away), never notice much smoke, but on way to moorland classics for a service it was smoking as described, no throttle, and in gear. got there and was told the mobil 1 i had bought was to thin! use the millers touring car oil now top stuff!!

 

think im looking at valve guides! im using a fully synthetic 5 40 i think,not sure now al need 2 check! even if it was wrong oil,wld it smoke as bad as it does? its not just a wee bit,its bad...

 

40 weight oils are only really suitable for very unworn engines/heads, perosnally even on these I wouldn't use anything less than a 50, but prefer 60 weight.
My experience of mobil is it does thin out a lot more than others PRO S is much better in this respect.
tabetha

 

cool. so wld the wrong oil make it smoke like it does?? and wot oil will i use? also,will i do the guides?