Breather system and oil consumption

[geoffinbc]

Yea I meant keep the PCV valve in place but change the breather tube to a small filter.

On 4.3L V6 engines and some V8's with TBI injection they had what people refer to as a puke ring below the air cleaner assembly. This was just a metal spacer with a tube in it to facilitate a breather hose. With this ring right above the TB it would allow oil into the air intake system and would cause all sorts of nasty buildup in the throttle body. So the solution was to ditch the puke ring and replace the breather hose with a small filter.

[3400-95-Modified]

The breather would remove the PCV completely. I don't recommend that at all. The PCV side is what sucks the crankcase pressure out based on engine vacuum. Putting a breather on will mean more crankcase pressure, which worsens the ring seal and lowers hp and mpg. Just run a catch can and keep the vacuum through the PCV.

I think he meant to put a breather on the rear valve cover vent, which is connected to the Intake PRE TB... so in theory there is no vac on that line ever... As noted the only time I can think of where it would contain a VAC would be when you go WOT and you have a slightly dirty air filter.

If you want to eliminate that pulling oil into the intake then just replace it with a tube going from your valve cover to one of these...

http://www.speedwaymotors.com/Dynatech-02-Pan-E-Vac-Kit,42754.html

http://www.shop.speedunlimited.com/p-5779-vibrant-11189-crankcase-evacuation-kit-weld-in-steel.aspx

I think you could replace the whole PCV system with this type of setup, but I'm not sure how they would work on our motors, since no one has tested something like this before. I'm half tempted to this year though.

[prophiseer]

Well, baffle is present (couldn't remember, lol) - oil pressure is good (optemp: ~40-45psi @ 700 RPM / ~55 @ 1500 RPM).

So, it's looking as if the only viable solution is an oil/air seperator for the PCV and breather sides. Joy, more stuff to cram under the hood . I guess I'll look into making my own, as this would be the cheaper route - I've got some ideas, so we'll see how that pans out.

[SappySE107]

The breather would remove the PCV completely. I don't recommend that at all. The PCV side is what sucks the crankcase pressure out based on engine vacuum. Putting a breather on will mean more crankcase pressure, which worsens the ring seal and lowers hp and mpg. Just run a catch can and keep the vacuum through the PCV.

[prophiseer]

If the baffle is indeed there and you are still picking up oil then It would seem you might have a lot of oil on the top end of the motor. You didn't run a high volume pump did you? What kind of pressure do you have at idle and what weight of oil are you running? Is your PCV valve new?

The breather line should be connected to the intake tube and the PCV should connect to manifold vacuum. Is this correct on your car? Also the breather line should be plenty far enough away from the throttle body to avoid being under vacuum. If you have a restrictive filter you may get a very slight vacuum on the breather causing it to suck oil out of the valve cover. You can replace the breather tube with a filter on the valve cover if you wish. Just remember to plug the hole in the intake tube.

No high volume oil pump - simply a new stock OE unit. Not sure of what current oil pressure is, I'll break out the gauge tomorrow and check (still haven't installed a gauge to the car). Oil weight is plain 'ol 10-30 ATM. After I finish out the first 1500mi I intend to switch back over to 5-30. PCV is new as well, I also swapped it out with a couple of known good units I keep in my toolbox (on the off chance it was defective), but no change to the condition.

PCV and breather are stock setup for a '99 3400. Breather line runs into the intake duct about 1.5"-2" in front of the TB. Should be more than enough distance . . . but, this motor is also pulling quite a bit harder than a stock 3400, too. Air filter isn't restricted, either - nice and clean.

You sure about replacing the breather tube with a standard or remote filter on a 3x00? Correct me if I'm wrong, but I've always been under the impression with these (and most other modern motors) that replacing the breather tubing with a standard old-school style filter will induce a vacuum leak, as intake vacuum is still pulling from the opposite side of the motor via the PCV. Unless, of course, the PCV were capped off, which is not exactly something I want to do with a street motor . . .

[geoffinbc]

If the baffle is indeed there and you are still picking up oil then It would seem you might have a lot of oil on the top end of the motor. You didn't run a high volume pump did you? What kind of pressure do you have at idle and what weight of oil are you running? Is your PCV valve new?

The breather line should be connected to the intake tube and the PCV should connect to manifold vacuum. Is this correct on your car? Also the breather line should be plenty far enough away from the throttle body to avoid being under vacuum. If you have a restrictive filter you may get a very slight vacuum on the breather causing it to suck oil out of the valve cover. You can replace the breather tube with a filter on the valve cover if you wish. Just remember to plug the hole in the intake tube.

[prophiseer]

I was pretty sure there was, too . . . but I might be wrong. My lazy self hasn't actually tried popping the PCV out yet to look I'll check it tomorrow morning as the car is sitting at my shop ATM.

But, alright then, in the event a baffle already exsits - that limits my options further.

How does a catch can change the vacuum? Its a sealed unit. I ran one on my old 3.4 DOHC setup (rebuilt) and yes, you have to drain it, sometimes very often, sometimes not so much.

Sorry, it's been a long day

I made a mistake in that post and stitched two different thoughts together. I had meant to say I had thought of simply capping the vauum line and installing a beather filter to allow for atmospheric ventillation - but this doesn't allow for proper crankcase ventillation . . . as well, the pull through from the breather side could potentially affect driveability as the intake would be pulling unmetered air from the other side of the motor - unless I installed a breather on the rear cover as well, and capped the port in the intake tubing. I realize a catch can is probably the only route, I'm just not happy with having to keep an eye on it (yes, I'm a mechanic, and yes I'm lazy as hell when it comes to my own rides ).

[SappySE107]

How does a catch can change the vacuum? Its a sealed unit. I ran one on my old 3.4 DOHC setup (rebuilt) and yes, you have to drain it, sometimes very often, sometimes not so much.

[bszopi]

I don't really have anything to offer, except there should already be a stock baffle in the valve cover...?

[prophiseer]

This has been irking me for a while now . . .

Complete rebuilt motor with a very mild build - motor runs great; still getting used to the chatter of having LS1 springs on the street It's built tight (like I prefer) . . . but, first experience building a "performance" 60*.

Anyhow, after extended periods at idle, the motor starts to burn oil - not a problem when cold. I at first thought this was simply the rings seating and thought nothing of it, but after 500mi break-in, there's been no change. Alright, must be buggared valve seals (they were a little tighter than I expected installing, but they still installed fine) . . .

Through this time I've also been fighting a weird chuggle/hiccup that would occur only at idle, and seemed more frequent after longer idle periods as well. At first I passed it off to higher intake volume, and the PCM simply going through fuel trim re-learn. Didn't go away, and in fact got worse the longer the vehicle would sit. No codes, PCM data all appear perfectly fine . . . so, I figure perhaps the IAC is starting to fail (200K miles on OE sensor), and decided to remove the TB to clean the passages and all . . .

That's when I notice the pool of clean oil sitting right at the TB inlet - front of the TB is bone dry, only the back side. Only way it could get there is through the PCV (possibly the breather tube, but doubtful). I decide to experiment and through a vacuum cap on the PCV vacuum line and drove the car a bit . . . go figure, the smoking has practically gone away, and so has the idle hiccup. I put two and two together, and figure the motor is pulling a hard enough vaccum that oil is getting past the PCV into the intake, and coating the plugs . . .

So - my question (sorry it took so long to get to it ) - any ideas on how to curtail the oil flow into the vacuum lines while still keeping an operable PCV and breather? I had thought of installing a remote catch can, but realize that could affect the operation of the PCV (change in vacuum), and would still have to be drained occasionally (would prefer not to have to). I'm thinking my best option would be to pull the front valve cover off and make some kind of baffle under the PCV port - but not sure if clearance is a problem with the rocker (at least, right off the top of my head - if need be I can pull it and check the clearance).

I'm more or less curious if anyone has run into this already, and what kinds of ingenious work arounds were implimented (aside from disabling the PCV/breather entirelly - which is out of the question)?