The Oil Catch Can

[yellow3800]

Oh ideas ideas.

Subject car: 2.8/3.1 v6

Forget you quad guys… that oil recirculation system is nicely done.

The v6ers however…

Our fuel injectors spray and this fuel spray goes past the valve stems to help keep them clean amidst the smoky oil air drawn into this by PCV (back valve cover) and the front vent that goes to the intake. This setup is largely good, and non of this is mandated, which is why we don’t have a topic in 20 plus years for this.

I’m addressing this because I drove my Indy (80k miles) hard enough to notice oil in the stock intake pipe a week later. THATS JUST THE FRONT VENT!

My 2.8v6 at 240k miles is still strong. But, is much more oily! Heck, I can smell oil while driving from the front that is vented and filtered. I removed its intake line a long time ago because it too put oil in the intake. Gook everywhere and I don’t like it.


I have found two types of “cans” on eBay at the moment. Dorman and others (summit jegs retail) are over $100 for one can and while I have decided to buy and not build, for my price of time, I am leaning on eBay specials, provided minimum design specs met like proper vent in/out (that popular $60 unit with filter on top is backwards) and I want a drain at the bottom. Back on topic!

One style is an air compressor filter style. Search ‘engine oil separator catch can’ to see this. Okay, 150psi limit! Ha! Heck, what little airflow we have…I’m concerned that it can’t push through a filter this fine.

Then we have the tradional style as we know them.

Now for IDEAS! on how to rig them.


I assume that we can’t blend front and rear valve cover vents to the intake manifold for vac leak/mixture reasons.

How about for the rear cover with the pcv, we remove the pcv valve, plug the manifold inlet for the pcv, run a hose to the front in parallel, to oil catch can, and then into the intake/air filter box as is stock?

Or get this fine mist of an air compressor filter unit, and put it inline with the rear pcv system, because it has more suck from the engine side, and put a traditional catch can on the front valve cover and run its exit line to its stock location?

What other ways can there be?

[Rettax3]

Hmm, great topic! I have run filters before, never a.. bad result... But haven't bothered with a catch-can... I should.

The rear (PCV side) is basically the engine-case's 'outlet' side when the engine is running at higher vacuum, such as idle, and engine vacuum will draw through the filtered intake duct and then through the front valve-cover, through the engine-block, then out through the PCV valve and into the vacuum-side of the engine. The engine will produce blow-by gas pressure inside the case, but this is allowed to vent via the front valve cover continuously, even at higher engine-loads and throttle settings when the PCV valve remains closed, so no problems with crank-case over-pressure. The PCV valve regulates flow into the intake-manifold's low-pressure (vacuum) side, and prevents back-flow, and actually allows 'fresh' air to be drawn through the engine, not just vent crank-case pressure.
Here is a quick simple video showing how the valve works for anyone interested: https://youtu.be/1UJDswbv1y4

Forced-induction cars have different concerns regarding crank-case breathing, and some cars are made so complex to deal with intake vacuum becoming intake pressure that they will stop being driveable if the PCV system is compromised... VW/Audi comes to mind as their ECMs are so extremely maladaptive (in some eras at least) that they will jack-up the fuel mixture beyond acceptable ranges and retard ignition-timing to After TDC trying to compensate for an internal air vacuum-leak, so bad it can render the vehicle unsafe to drive and eventually destroy the engine. I've had the 'pleasure' of working on a couple of these, but it gets easier after figuring out the problem the first time...

A catch-can could be made out of almost anything, provided that it will handle engine-bay temperatures and the erosive crank-case fumes, and the moisture often trapped in the gasses. I completely agree -a drain at the bottom is ideal if not strictly necessary, and the can should have both inlet and outlet ports, and allow airflow through. If possible, baffling would be ideal to help break moisture and contaminates out of the 'air', and allow it to drain down to the bottom. Placement? Probably between the PCV valve and the intake vacuum-side is best, so maybe on the firewall? Below the intake manifold inlet port, above the oil-pan. Leave the front valve-cover fresh-air side alone, or better still, replace the vent tubing with a filter to keep those nasty crank-case gasses out of the intake entirely, yet still allow case venting, and plug the intake duct from the filter to the throttle-body... Now for the crud exuding from the EGR system into the intake... YUCK! "Egger" doesn't ride with me in my cars...

[woody90gtz]

Here's a post that shows how I did it. Cheap ebay catch can, breather for rear cover, vac line from PCV to catch can and catch can to vacuum line that originally went to PCV.
viewtopic.php?t=3868&start=1558

[yellow3800]

Thanks for the input guys!

Eric swaps the front and rear covers operation and catch can in line with the pcv side. Nicely done.

Good video - the last time I checked the pcv on my high mileage 89gt, I just shook it to judge how clean it was. Forgot about the spring strength! I bet it’s gone by now. Gotta check that. Aside from that, I’m contemplating tying the front to suck into the manifold line somehow, catch can on that pcv/rear side and we’ll see how the hole size effects vacuum. Air is defiantly escaping from that front valve cover now, not sucking in. I smell it when I daily drive. Oil vapor everywhere. No I’m not rebuilding the engine, but that’s probably the proper way to fix it!
Maybe a larger rear manifold port for increased volume but then mixture will surely be effected. Hmmmmmmmmm

Rettax3, egger disconnected on my vaccum 89 and it runs so nice. My stock Indy is half “digital“ (throws a code but doesn’t kill other systems when it’s screaming foul) and when it’s on, I lose 5” of power above idle… just goes to a deadzone, choking on its own… Otherwise the egr is good. If I learn how to tune, and provided that it can be done, I’m gonna block that first 5” of power … no egr operation there.

[woody90gtz]

I saw you both mentioned PCV being on the rear valve covers...must be an MPFI thing. Both my SFI engines had the PCV on the front side.

As I recall $A1 mask, the EGR has a table with injector base pulse width vs % to compensate for the lack of oxygen in the air charge with active EGR, but I don't recall a way to partially delete it. The spot in the tune I used to delete it was EGR coolant temp enable and I just cranked the value up to like 256*F.

[Rettax3]

I saw you both mentioned PCV being on the rear valve covers...must be an MPFI thing. Both my SFI engines had the PCV on the front side.
As I recall $A1 mask, the EGR has a table with injector base pulse width vs % to compensate for the lack of oxygen in the air charge with active EGR, but I don't recall a way to partially delete it. The spot in the tune I used to delete it was EGR coolant temp enable and I just cranked the value up to like 256*F.

Yep, the older MPFIs (2.8 and 3.1) put the PCV in the rear cover, harder to access for no real reason except the engineers never have to work on the crap they design. Of course, the serpentine belt could be replaced without jacking-up the engine and removing the right-side engine-mount on the older engines, so there is that as a trade-off... I find it amusing that my 3.4 DOHC LQ1 monster is easier to access all six spark-plugs than on the pushrod engines, of either Generation...

Woody, I like your way of fixing the EGR 'problem', I do wonder if the ECM knows the EGR is malfunctioning if it will leave the fuel mapping alone? I can't say I've ever noticed a problem with mine, after blocking-off the EGR on the intake side on any of my 60-degree V-6s, and on my Yellow Indy I used to be very conscious of how it ran at those lower throttle settings, because I was always having to run it through my neighborhood in that tiny sliver of parameters that would allow lock-up of the TCC in the transmission and still not be speeding nor bogging down the engine -it was right in the speed range that I had to get the clutch to lock then slow down a few MPH to the speed-limit but not enough for the TCC to disengage again... Darn that digital cluster with the instantaneous MPG display!

yellow3800, so we are discussing eliminating two separate symptoms, right? The oil-vapor smell, and the residue left by the PCV system in the intake duct and the manifold. If you keep the front (MPFI setups) 'vented' side hooked-up to the intake duct, it will still blow muck into the engine, even if you have a catch-can on the other side of the system, but I think if you run a filter on that end of it with your engine's condition, you will probably continue to smell those oil vapors... Two catch-cans? Hmmm... Seems more effective to have a catch-can on the 'vented' (non-PCV valve) side, two cans seems a bit ridiculous.
I wouldn't think enlarging any of the ports or lines should be necessary -the blow-by gasses are obviously worst when the engine is at WOT, and in that case the front 'vented' side will get large volumes of airflow pulling past it and diluting the oil vapor and blow-by gasses -probably not much of any vacuum draw, but there may be a slight Venturi effect pulling air past the port in the intake duct (you could use a small piece of tubing extending into the duct through the vent-line port, cut at an angle with the taller side facing the airbox to create a definite vacuum on the line so long as you could ensure it couldn't get drawn loose into the intake duct and into the engine)- but the air-flow into the engine should eliminate the vapor smell. Then, on the PCV side connected to the intake manifold, although the vacuum will be minimal due to the throttle-body being open, there should still be enough to draw any gas-pressure out if the spring in the PCV valve can unseat. Either way, you shouldn't smell any oil-vapor from that side of it, if the hose connections and PCV grommet remain tight. Is there another gasket or seal leaking somewhere that is causing the oil smell? If the engine is so far gone that it is developing positive crank-case pressures despite a well-operating PCV system, yeah rebuilding would be the 'correct' fix, but is it worth the time to hook up a temporary pressure-gauge to verify the condition? Especially if you don't want to invest in a rebuild anyway? Probably not, but it would be interesting to see the results!

[yellow3800]

Okay, finally got around to messing with this. The main prob on this 89gt is oil smell, evidenced by oil residue all under the hood and surrounding the valve cover (front). New valve cover gaskets and grommets both front and back. Yes I cleaned it well! Gotta add some sealant from a tube on these to do it right. It’s obvious that oil is coming out of the front valve cover that currently has a breather filter installed.

Here is what I did: I wanted to see if eliminating the PCV valve itself would suck more. It does but it affects idle too much with too much air. So I’m gonna put one or two pcv valves in and see how that goes. Spill opinions here please. I do not know how the 3800 pcv system works (it’s internal - never messed with it) or anything newer than 2008ish model years. I do know how we got here from 1950 however. It’s a slow technological improvement.

No I have not compression checked the engine for info reasons. It gets full mpg and is strong as new so I don’t suspect any bad valve area… now there IS a crack in driver front cylinder wall from top to bottom… so maybe this is pushing air on its compression stroke to the pan area… but haven’t verified that. Don’t care really. When I drove my low mile Indy hard, it throws up oil in its stock airbox so this is a test bed for that too.

The oil catch can can’t be fabbed by me for cheaper than an eBay buy. $18 did I spend? It comes with a top breather filter and draincock in addition to the standard in and out line ports. Also comes in small or large! I’m impressed. Retail or the best option otherwise is $120. It looks like a quality deal!

I attached the manifold suction line in back to the out of the can (some YouTube say that it’s reversed… mine is not) and then I connected the front and rear valve covers together through a TEE fitting on the 3/8” vinyl tube used here. This line goes to the other port, IN , of the oil catch can. This will draw from both valve covers into the separator.

I think it’s the same s Eric’s except that I don’t have pcv valve(s) in at posting. Don’t know if his ambient air filter is used. I wish that I didn’t hollow out my pcv valve for the first test.

Premature post, I’m going to add one or two pcv valves and try again. Idle is 1100 in this setup. When the manifold input line is plugged the idle comes down nicely. Oil cap suction is massive. I’m impressed for a 3/32” stock ID hose dia that runs to the stock pcv valve. Takes less than 10sec to develop full suction I’d guess.

Can is mounted behind driver side headlight. Pix show vinyl hoses run and the rear of engine. For behind the headlight pic, follow the vinyl hose in to barely see the can.

The optional breather filter can be put ontop of the separator can. I didnt use it because I wanna suck vapor from that front valve cover. I don’t see a prob without a fresh air inlet. I worked on an 08 audi once and it has this strong vacuum sump.

Please comment and I’ll post new findings with pcv valve(s).

Andy

[woody90gtz]

So, where is your crankcase getting fresh air? I'd assume it's not then, correct?

The factory line that goes to the air intake tube is the one that supplies fresh air to the crankcase. It pulls from that tube so that you're not bringing dirty air in to the crankcase. If your PCV is set up correctly to manifold vacuum, that line from the valve cover to the air intake tube should always pull from the tube to the crankcase, and not let crankcase oil into the intake tube.

Mine was essentially a factory setup, but with a catchcan inline between the PCV in the valve cover and the manifold vacuum. As I recall I had to delete the line that went to the air intake due to plumbing, but I put a little filter on an elbow in the valve cover so that the air going into the crank case was still filtered.

I think if you copy that idea it will give you the best results. Filtered fresh air into the crankcase, and oil mist separated before entering the manifold vacuum.

[Rettax3]

^^^This.^^^

I had experimented on the 305 in my 'old' Camaro back in the day, before I had any real idea that the PCV system was more than a glorified crankcase vent. To be honest, while I would still suggest a fresh-air inlet and a vacuum outlet, it is probably not horrible to the engine internals to simply vent the crankcase and not supply a continuous flow of fresh air through it. Might even reduce the amount of moisture build-up inside the crankcase after the engine begins to cool...
On the 'old' Camaro, I had used clear PVC tubing tee'd to both valve-covers and piped into the vacuum-supply off the throttle-body (familiar? ), but in my case the setup was a total fail because the combination of engine-bay heat and vacuum off the engine collapsed the tubing, preventing it from even being an adequate vent. Fortunately, I caught the problem right away, and instead installed a breather-filter in one valve-cover and (IIRC) replaced the other valve-cover line with a conventional rubber vacuum-hose to the throttle-body's vacuum-port. This was before I replaced the TBI intake manifold with a heavily ported CFI manifold, but now I am thinking about it, this might well have been after I swapped the 305 with a 330k+ mile GMC 350, because of a suspected cracked piston-ring in the 305 right at 100,ooo miles.. Almost sure I re-installed the PCV valve back in line too at this point. Never did do the catch-can though -I should have. [Shrug.] But I never had oil-vapor issues from that car, only exhaust-smell from a loose pipe after the catalytic converter. Man, that was a long time ago...

Andy, you kind of lost me at "there IS a crack in driver front cylinder wall from top to bottom… so maybe this is pushing air on its compression stroke to the pan area… " Do you mean the cylinder wall itself is actually cracked all the way from the head-gasket surface area (the block's "deck") down the the bottom of the cylinder?? Blowing ~120-psi compression-air into the oil-pan wouldn't be my first concern -blowing 1,000+ psi combustion-gasses into the cooling-system would be, that and sucking coolant back into the cylinder during the intake-stroke and while just sitting, not to mention possibly leaking coolant directly into the oil-pan. I don't think this is what you meant, I'm just not sure though.