GregBBRD

Keep in mind that because there are not any vents in the cam carriers or the heads, on these 2 valve engines, the only place that the engine can vent is at the filler neck.

For what it is worth, I've never been able to run a filter/scrubber in the filler neck area of these engines. I've found them way too restrictive to allow enough air to escape. I believe that the best one can do there, is to try and deflect some of the oil and separate the air from the oil somewhere else.

My guess is still that you are either building crankcase pressure or stuffing oil into the intake.

docmirror

Isn't there an aneroid manometer pressure check for the 928 crankcase? Maybe it's only the 32 valve, but I could swear I saw a guy with a tube manometer making a pressure check somewhere in the WSM. hmmmmm

Imo000

Yes, I fully understood those numbers and that's what I based my comments. If the difference is more than 10%, you have a real problem and the cylinder is not sealing well. As I said above, the leakdown % should be less than 5%. At fhat rate or less, you'll barely hear the air leaking and all the leak would be through the rings.

Ducman82

copy that. i read your post wrong. :-S

slate blue

Sorry to hear of your dilemma, I have a 5.0 liter also, it was built with parts that I personally checked which was a mix of old and new but the wear parts were mostly new except for the pistons and valves. The engine's filler neck can be opened and when hot there is no gasses escaping there at idle. When you rev the engine, (no load) there is very subtle steamy sort of gas vapors but minimal.

The engine has done around 3,500 kilometers before I stopped driving it but the was never anything in the U bend of consequence, maybe one or two ml of oil after that distance and many dyno runs. The engine does have crank scrapers. When the many dyno runs were done in a unvented workshop, my car was the least smokey of all of them. The car hasnt used oil in the the said 3,500 kilometers.

The reason I mention this is you shouldn't go thinking that blowby in these engines is normal or exceptable. I also believe that when you have sealed up an engine properly it will produce excellent power, which this engine does.

My guess is you have problems with all aspects of the sealing surfaces. I would like to know the piston to bore clearance, the ring clearances in the pistons, maybe you have excessive flutter? The valve guides as others have mentioned may also be crook. Valve guide clearance is important, if you have it too tight or loose you will loose power. Most people don't realize how you loose power if the guides are too tight. However they can't seat themselves properly when too tight.

I would never vent the engine to atmosphere, I think you should find the cause of the problem and this won't be needed. I'll follow the thread and provide what help I can.

G8RB8

He's got a lot of blowby. In another thread I suggested opening the filler cap and starting it to check. He misunderstood and actually drove it like that and blew oil everywhere.
My theory is excessive blowby is swamping the vent system and building pressure in the crankcase, which then forces oil up past the rings, or maybe past the valve seals (I doubt that though)
Duc please correct me if I'm remembering this wrong.

Ducman82

^^^ yes i did!!!! such a mess^^^

This thread is just full of good advice and ideas. thanks a billion guys!

here is my game plan

clean the plugs and button her up and just DRIVE. not idle and move stuff, i mean highway speeds etc.
then when home let it cool for a few and take the plugs out and do some checking!
rotate the engine and close the intake valves on atleast one of the "trouble" cylinders and sit back and relax for a day or so
then pull the intake center re check with the camera and see what i can see.

my breather issues were two fold. my stupidness had me plumb in the provent straight to the center of the engine with no splash guard of anything. so the crankcase exhaust evac system just filled the provent with oil, filled the line to the exhaust one way and then the exhaust with oil/hence WWII smoke screen.
i added the scrubber and made the oil fill neck taller to allow suspended oil a chance to fall out of suspension, problem was solved!
now i think the exhaust one way valve just does not work. it does not pressurize the case, but does not create suction like it use too. i think thats when all this started this time.

i only have about 400ish miles on this car. rings need to seat, rings dont need to seat, either way i need to drive it some!

ill keep everyone updated with my tests!

LT Texan

well? Let's hear it. I bet it cured itself....

Ducman82

Almost! Been freezing here and the kiddo (almost 2) was real sick.... Got the vacuum pump plumbed up, just waiting to weld up and adjustment bracket and she will be ready to go. Should be Monday night.

Ducman82

OK

did a few mods here

Added a GZ motorsports VP102 vacuum pump to help with ring seal and breather issues. pump pulls from the custom filler neck (12AN line) to the pump, then feeds that air in to the pro vent. provent "out" line has a breather fitting on it, and the oil return line feeds to the driver side cam tower (4AN line) so the Pump will suck in fresh air and any oil that collects.



i also added a Kuhn performance filter system with my ABS shroud on the back of an S4 upper rad portion. the cone in the back is a little to the pass side, so the hose back to the intake is a little off, but works perfect.

under hard acceleration (hard as i was going to try on this Cold RAINY day, the pump pulls 12-13Hg. No smoke No Mo'..... YAY

Lizard928

Good to see Jake,

keep monitoring the provent outlet for oil. I am not 100% sure that the provent is that great for this system.

For those wondering this is what I have done to my car. Oil consumption will go way down. But just be 100% sure that you do NOT exceed 15" Hg vacuum in the crankcase, without doing some serious mods to the motor.

Ducman82

provent had a little oil in it, not much. but enough to lube the pump. and thats WITH the Kuhn Scrubber installed.....

Lizard928

I would still remove that scrubber to allow the oil to be fully pulled out of the cloud.

G8RB8

Sounds like you're on the right track Duc. Glad you got it sorted.

LT Texan

Great news!

I think I remember reading years ago that crankcase vacuum reduces effective oil pressure?