Monkian

Morning , Hoping somebody in the know might be able to help me

I've just rebuilt a V5 STi engine with new parts as a big end bearing went on one of the Rods.

Brand new:

MAF
Crank
Gaskets and other parts to get it back and running.

I de-glased the bores and regapped the rings accordingly

Its all back together now but I have a couple of problems problem and I'm not sure if they are related.

I can hear one of the inlet valves hissing when I turn the crank over as if there is a leak so i know I need to replace it.

On cold startup the engine starts up on the button but bellows out blueish/grey smoke for 5 mins .. It idles crap and sounds like it want to stall (slight crackling in the inlet mannifold on throttle blip. then when its warm it totallay clears away..and runs ok.. it also puffs a little smoke on load when warmed.. not much tho.

Would this just be related to the leaky valve... or will i have a lamda problem as well... just wanting to get to the bottom of it all now...

Help appreciated

Slowboy Racing

Did you change the valves or do any work to the heads? If not I can’t see a reason why the valve would all of a sudden be a problem. Are you sure it’s not the valve opening and releasing the compression when you turn it over manually?

If however the valve was not closing or seated properly it would cause poor running. But this should not account for the smoking assuming valve seals are all intact this should not allow oil into the cylinder.

I would be interested to no from above if you replaced your original rings? Or are you saying you re gapped your existing rings?

I would carry out a compression test at this point to give some Idea of ring seal.

And i am also hoping you replaced the oe oil cooler on the build.

Neil

Monkian

Hi Neil , I used the orginal rings . they were fine beforehand with no smoke ..

No headwork The engine had a dodgy big end so the piston could have touched a valve briefly and move it out of place.. visually it looked ok . but that means nothing in valve world

The only reason why I'm pointing a towards the a possible valve sealing issue is that I could hear it not sealing propperly when I turned it over by hand.. hissing .And can hear it ticking away(only just audioble over the injectors) but deffo from the passenger side head so it sounds as if its not seated proplerly. I've now started to dissemble the engine to its too late for a comp test but it has to come out anyway to change the noisy valve/s




I also used a new oil cooler and filter as well there are a host of other parts I have replaced as well.

I'm also getting some oil in the intercooler and turbo outlet which I wasnt getting before It was rebuilt.. I know the turbo is fine... But am i'm not 100% sure if the leaky valve (inlet and possibly exhaust) would cause such side effects.


Any more for any more
??



Cheers

Monkian

anyone?

Slowboy Racing

I am not sure why you would re gap your existing rings they should be fine? You need to do a compression test...

If the rings are not sealing properly you will get excess blow by gasses this in turn will increase crank case compression and also increase the chances of oil getting into the inlet via the pcv system, even if the piston did tap the valve which I very much doubt it wouldn’t explain the oiling.

If you don’t have a compression tester to hand check the crank case breather for excess vapors I would confirm this first then maybe look at other options.

Neil

Monkian

cheers , just checked the valves.. they are all straight.. but i re-lapped them in just to be sure.

On closer inspection it looks like all of the intake pipes have oil in it....also the intake of the exit and intake of the turbo has oil in it too...

would this be excessive crankcase breathing?

if so I can only gather is piston rings that are bad.. and apossible rebore?

weakboy2

sounds like the turbos given up mate

Slowboy Racing

IMHO The Best thing you can do is have test done eliminate this first, if all looks good there then look at other options like the turbo otherwise its just working blind.

Neil

360ste

iTrader: (1)

Before you re-build why not price up getting the bores checked to see if a re-bore or honning is required and then fit a new set of rings correctly gapped. It would then eliminate any problems with the bores and rings. It seems daft to me to rebuild the engine, re-fit it get it running only to find the problem is still there then have to remove and strip it down again

p1mark

Agree with Neil.

Putting old rings (even if they are fine) into a honed or even glaze busted bore is not clever. When the ring is new, it has a coating on that is designed to bed in with the bore.

Putting a ring that has been bedded into another cylinder surface is not giving it a chance to seal correctly.

The blow by will be causing your excess c/case pressure, and venting off into the intake system.

Compression test, and/or a leak down test may confirm.

Monkian

Right , stripped the blocks down inspected everthing.... after 50 miles of usage the ACL bearings look in perfect shape the bores have slight.. (very slight) marks on them when the engine gave up on it previously so I'm going to have it honed professionally within tollerance and fit new rings and Valve stem seals just to be sure.



If it still happens after this it got to be the turbo..

I'll keep you posted. thanks for your help.