Advice wanted for on-going blow by issues (long)

[Grover]

Some months back I started burning significant amounts of oil (1qt per 750-1000 miles) and it appeared to be coming out of the tailpipe. Primarily it happened during acceleration after sitting at a traffic light for a little while, or after taking the car up to high revs, lifting off the throttle and then getting back on it again. In both instances, large grey puffs would be visible out the back windown. A leak down test showed that my rings were "perfect" but that I was getting leakage through the valves. In turn, I had a head rebuilt with all the "right" seals and everything, but after now driving with that set up for about 1,200 miles, my oil consumption is virtually identical and the blow-by issues have not gone away. I moved to a hotter plug and dino juice (vs. Mobil 1), but no change seems to have come from that either. The motor itself was fully rebuilt about 30k miles ago by a reputable BMW tuning shop in So. Cal.

So where to go from here? More than anything, I just want a firm diagnosis so that I can get in there and fix it once and for all. One person has suggested that perhaps my compression rings are "perfect" but that the oil sweeper rings are poor, leaving oil residue on the side of the combustion chamber. Does this make sense? Would this not be illustrated on a leak down test? Any recommendations on how I can solve this would be greatly appreciated. TIA.

[c.d.iesel]

"""......had a head rebuilt with all the "right" seals and everything...""" virtually identical

but ....are the valve guides really NEW ?, and how about the valve stem to guide i.d. clearance ?, and how about the care which the valve guide seals were installed onto the guides? .....and when the valve stems are inserted into the NEW seals - were any nicks, tears caused from not using the 'condoms' for protecting the seal???

all of your oil smoking conditions is from/during high intake manifold

vacuum conditions - ie 'overrun' . Your cylinder leak test shows that no broken/leaking piston rings, ..... and bottom end induced oil smoke is during 'load' , on-throttle conditions - not 'overrun'.

re-visit a cylinder leak test - carefully!

check spark plug color after extended use to evaluate which cylinder is oiling

not to over look also a radiator/cooling system pressure test , Hot & then Cold.

and what sort of crankcase breather are you using? - if the hose from the cam cover is routed to the air cleaner - disconnect it and route it to exit below the front subframe or into a catch bottle. Is there restriction like a 'filter' on the cam cover breather fitting? remove That now. With the motor running, is there vapor and pressure exiting the cam cover breather fitting?

http://autos.ph.groups.yahoo.com/group/slash2/photos/view/c41c?b=8

[SteveJ]

Grover,

I have a Stant pressure tester for your cooling system tests. Come on by some evening to give it a shot.

I also have a BlockTester, but cj is borrowing that right now.

[Grover]

Thanks for the input. CD, honestly some of your questions are over my head and I can't provide the details of EXACTLY how the head was reassembled. A trusted friend, and very knowledgeable FAQer spec'd the head rebuild for me, and I have no reason to believe anything was awry with the rebuild.

As for the breather, the hose currently runs into the bottom of the Weber carb, but us a test I put on a new hose and ran it directly to a catch can. No change in blow-by happened during this time.

As for the cooling system, if that were the issue would the smoke not be burned coolant as opposed to oil? Again, perhaps I am just not knowledgable enough to completely understand your question, so please feel free to elaborate, I greatly appreciate your input. Also, as for doing another leak down test (or do you mean compression test) why do you state that this should be approached "carefully"?

Thanks SteveJ for the offer, let me know when CJ is done with the tester and I'll arrange a trip out your way.

[SHEN]

This is simple but put some duct tape around your dipstick to seal it better. This oil consumption can easily accrue because of a vacuum leak in the block. It makes it much easier for oil to pass the rings no matter how good they are.

[o2pilot]

I have had the same issues with an older subaru and remberered the same issue in a peugeot 505 turbo that I had years ago. Both were burning oil at an alarming rate. Funny this just came up in the subaru and I thought how did I combat this in the 505 turbo. In the 505 I filled the cylinderers with kerosene on the advice of an engineer from Garret (the guys who built the turbos) to loosen the rings as they were probably "stuck". After a weekend of soaking

and changing the oil all was well. This was 15 ys ago. The subaru is current. It was burning 1 qt/ 500 mi on a 170k mi engine. I added 1 qt marvel mystery oil (basically kerosene, etc) to the oil and comsumption has been nil in the last 2k mile. Just my 02 cent worth. o2pilot

[Guest Anonymous]

My two cents...if grey smoke out the pipe isn't that overly rich fuel mixture...I thought blue smoke was oil...maybe you need to look at your carb jets or sticky choke...something like that. And maybe your oil is a real leak not burning...what about that!??? Pete