so here it is the block is B20B w/ probe rods and arias high comp. pistons... the head is the stock head mild port/polish, ferrea SS valves, crower dual springs and ti retainer set... machine work was done at the machine shop... i just bolted the head on the block.... heres the deal ive started it only 5 times each time let the car sit above idle for about 30min... the first time i started it it smoked alot... i thought this was completly normal... i assumed it to be assembly lube on the cylinder walls.... well its still smoking A LOT... blue smoke so that = OIL.... so now with about 2.5 hrs of on time theres no way its could be any sort of oil on the walls... and this thing smokes alot.... so i pulled the plugs and yes they are black and wet with oil... not soaked but there was oil.... looking in the sparkplug hole i can see a thin layer of oil on the piston tops... all 4..... so now that im shitting bricks i did a leakdown test.... leakage was less than 8% across all cylinders when warm.... the valve seals are all new as well..... so yeah its burning a shitload of oil but yet has perfect leakdown.... looks to be evenly in all cylinders from the look of plugs and oil film on the piston tops.....


so anybody ever have this issue? im lost.... the only thing i can think of that would cause oil burning and good leakdown are the valve seals and those are new as well.... i checked them just incase and looking through the springs they look fine....
oil press at idle is about 26psi and above idle reaches about 70psi....

anybody?

 

check your intake manifold and if any oil has gotten into the intake ports, i had a problem with this, my charcoal canister (black box behind block) had a problem and was shooting oil into the intake, if there is oil there, trace to find how the oil is getting in, if there is no trace of oil, keep me posted

 

the block im using doesnt have a canister at the back.... my pcv valve goes to the valve cover...

 

oh yeh, i forgot the B20b, the newer ones, another b20 i had had a problem like that, it had a lot of pressure built up in the crank case, when you take off the oil cap or the oil stick does it shoot out alot of pressure?

 

some but not anything excessive...

 

You've let a newly built engine idle for 2 1/2 hours and haven't loaded the engine up at all? Hmm, this may not be such a good thing to do, you might concievably have glazed the bores.

A newly honed / ringed engine should be started then quite soon placed under some significant loading in order to get some pressure behind the rings and 'push' them harder against the bore (not thrashed of course). If you don't do this then the rings only rub lightly which may cause glazing on a fresh bore (so I understand, could be wrong, I do know from experience that you can't be too gentle running in a newly honed kart engine or the bores can glaze up). This could cause oil loss.

Most of a rings sealing doesn't come from ring tension, but from gas pressure behind the ring pushing them outward. The ring tension is there to provide enough seal for pressure to begin building behind the ring on the compression and then combustion stroke, though of course it provides the seal required on the induction stoke and some portion of the exhaust stroke when pressures are low or negative.

 

the car has sat above idle for 2.5 hours but 30min at a time.... after each time the motor was let to completly cool. and if blowby was occuring because of ring issues it would show on the leakdown test... so im pretty sure thats not the issue....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by toofast4u752 &raquo;</TD></TR><TR><TD CLASS="quote">the car has sat above idle for 2.5 hours but 30min at a time.... after each time the motor was let to completly cool. and if blowby was occuring because of ring issues it would show on the leakdown test... so im pretty sure thats not the issue.... </TD></TR></TABLE>
But even so, it's idled with no load for quite a long time, that time being broken up into shorter intervals notwithstanding. Have you driven it at all yet? I'd take it for a spin and hope the smoking lessens or disappears.

I'm not saying glazed bores are definitely your problem, but past the rings is the most likely place substantial amounts of oil will enter the combustion chamber.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by johnlear &raquo;</TD></TR><TR><TD CLASS="quote">
But even so, it's idled with no load for quite a long time, that time being broken up into shorter intervals notwithstanding. Have you driven it at all yet? I'd take it for a spin and hope the smoking lessens or disappears.

I'm not saying glazed bores are definitely your problem, but past the rings is the most likely place substantial amounts of oil will enter the combustion chamber. </TD></TR></TABLE>
like he said you need to seat the rings. expecially sive the motor has forged internals and the piston to wall clearance is greater than factory.
i would take it up to redline in third or fourth gear and let the motor drag itself down several times. that may help. also a catchcan may help with the lack of ventalation. if the oil rings are shot then the compression test and leakdown test are gonna be good but your still gonna burn oil.
also was the motor professionally build. did the bore the cylinders to the manufactures specs

 

the bores were oversized to fit bigger pistons.... i have came to the conclusion that the valves seals were installed incorrectly...i pulled the exhaust manifold off and there was visible oil in all of the exhaust ports... looking closer i could see a drip of oil coming down one of the valve stems.... so yeah it looks like the intake valve seals were put on the exhaust side and the exhaust on the intake side.... well at least i wont have to pull the head.... it will still be a mayor pain to change out the seals with the head on the block.....

 

Well I hope you're right, but I just can't see enough oil passing down the fairly tight clearance between new valve stems and guides to cause visible smoking, even if no seals were fitted at all. Some engines don't even have seals fitted to the exhaust valves, and it doesn't cause excessive oil consumption or burning of oil in the pipe.

Even with somewhat worn valves / guides I still wouldn't expect all that much oil to pass into the exhaust from this source, the exhaust gas pressure will if anything tend to push excess oil back up the guide. Some negative pressure pulses in the exhaust flow may draw some oil all the way through, but I'd be surprised if it were much. Also, it would likely be more with a hot engine that had been shut down for a while because the positive exhaust pressure would be removed and allow hot thin oil to dribble down the guide / stem in to the port, where it waits to be burned the moment the engine is restarted.

I once had an old Holden (Aussie GM brand) with significantly worn valve stems / guides, and on which most of the ehaust valve seals had perished and cracked up, this car did blow some smoke, but it wasn't very much, barely noticable. This engine also blew more visible smoke on start up than it did once on the move.

Lack of seals on the intake valves might cause more oil burning because the negative pressure in the intake port will 'suck' it in.

If a substantial amount of oil is getting into the combustion chambers past the rings then it's not really surprising to see it in the exhaust ports, not all of it is likely to be burnt and will pass into the exhaust.

Sorry to be so negative about this!





Modified by johnlear at 4:26 AM 1/28/2008

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 4g hatch &raquo;</TD></TR><TR><TD CLASS="quote">
i would take it up to redline in third or fourth gear and let the motor drag itself down several times. that may help. </TD></TR></TABLE>

I would strongly advise against high rpm on a freshly built un-run in engine. My advice would be a few runs at WOT up to say 4000rpm then back off. This will put pressure behind the rings and help bed the rings and bore in, but high rpm may well do more damage than good (to the rings and bores and other things).

Keep in mind that it's not only the rings and bores that need to be run-in, but also the cam lobes etc. Also keep in mind, if the bores / rings are already glazed it may be too late to do much about it, other than re-hone and re-ring...