Just finisheing up a rebuild, the 302 is now a 347, and installed a non vented catch can between the pcv valve and the upper intake on the passenger side. Now I'm thinking about installing one on the driver side between the oil filler neck and intake tube, I'm sure oil gets sucked in there also. The one I installed uses 3/8" hose. Not a lot of room to mount one on the drivers side so I'm looking at a smaller water/air separators that are mainly used on air compressors. They all use 1/4" ports, would that be too small? Anybody else here running a catch can or separator?

 

you don't need one on both sides. Where are you running the breather on the non-PCV side to?

 

On my 94 I have a K&N cold air kit and there is a rubber hose that that runs from the oil filler neck to the side of the K&N intake tube. I would like to install an inline separator in between. I just pulled the upper intake off while back and there was an ungodly amount of oil build up in the plenum.

 

That is a sign of something amiss. A catch can is just a band-aid fix IMHO. A new or newer engine with "ungodly amount of oil build up in the plenum" is a sign of excessive blow-by.

 

Unless you're running sick compression, or forced induction, rla2005 is exactly right, a catch can is just a band aid. And adding a second one isn't going to accomplish anything.

 

I have a catch can on mine, and it seems to have the same amount of oil in it as it did before the engine was rebuilt. Seems to me that the PCV system captures a bit of oil, and it is just normal. It is consumed by the engine with no great impact on anything. Over time the PCV valve may get gummed up, but that is why it is a tune up check and replace item.

Because of the Edelbrock intake design, the oil tends to drain into the throttle body when the engine is not running and gets into the TPS and so forth... so I have a catch can I check and drain every now and then. On a stock set up I didn't bother, and wouldn't advise someone else to bother.

What would be a nice solution is a mesh screen below the PCV valve in the valve cover to prevent the bulk of the oil from being picked up in the first place, not that it proved all the effective for those running GT40 style intakes.

 

Judging by the incredible amount of built up oil residue and gunk that was inside the upper plenum on my stock setup there is a lot of oil being being sucked into it over time that does not leave. It took a lot of effort and time with a long flexible dryer duct brush and purple power to clean that mess, There's only two places that allow that by putting vacuum to the valve covers and pulling it into the intake. To me it seems inevitable that it will happen again without a catch can or separator in place. It may take a long before the build up is enough to hinder performance but eventually it will. I'll probably go with this separator on the driver side. All total I'll have about $50 invested for both units. I had a 2003 Lightning that I eliminated the pcv system altogether and installed an electric vacuum pump plumbed to one valve cover and a small air filter on the other to pull fresh air through the motor into a catch can and out to a filter at the back of the truck. The stock pcv system put a lot of oil residue on the intercooler witch really hurt charge cooling. It was a real pain pulling the SC and midplate to clean the intercooler. Not going to get that involved on this N/A motor, just what I noted above. I appreciate the replies.

 

Yeah, the crap is a mixture of the PCV oil and EGR gasses... it does make a nasty coating. I don't see what a separator will do on the drivers side as the air is "supposed" to be traveling into the valve cover not out of it. Curious if it will catch much of anything.

 

mine was $9, including the 2' of 3/8 hose, Harbor Freight, works great, old age, and long in the tooth, responsible for mine(183,000mi), but not near as bad as I first thought, maybe a thimble full between (3,000mi oil changes).

 

I don't see how it could be traveling into the valve cover. The other end of the hose is in the intake tube which is under vacuum. Seems like it would pull into the tube. You may be right though, there is more vacuum in the plenum and air could be pulled that way. Being it's so cheap, I'll install the separator on the driver side and see what happens. If nothing happens I'll remove it. Be a good test if nothing else.

 

Is that on the pcv side?

 

Yes it is on pcv side, maybe your driver side is the issue, being on wrong side of filter, and it pulls the oil out(path of least resistance), I know you know, but that side is actually under the filter in filter box, and also has a mini filter on that small hose, to keep it from pulling vacuum on that side, but in your case your right it does have enough vacuum to pull from that side being so close to throttle body? maybe?

 

Many of these trucks I have seen over the years with the mass air type intake tube had oil in the intake tube or throttle body that was being sucked in through the breather side. I have also seen the speed density setups where the breather is in the air box with a separate filter and that is covered in oil. I'm not really sure how that side is not supposed to act similarly to the PCV side since it is creating a vacuum and being sucked into the intake in nearly the same way. I would think that the breather side should be vented externally from the intake, but even a lot of 70s and 80s carburetor setups had the breather connected to the air cleaner, do to emissions. I've cleaned out these intakes a few times as well, and I think most of the crap is related to EGR gasses and the oil film just makes it worse. I have never run an oil catch on any vehicle, although I have considered it before. If it was that important, I would think that it would have one from the factory, and I have never seen a vehicle that did.

 

Yes, they used to vent that line to atmosphere, they were called road draft tubes. And I consider them irresponsible nonsense, unless you've got something that is some sort of concours level collectible. Don't dump your junk on the ground.

 

Not needed. The filter to oil fill neck is the fresh air INLET to the engine. It is there to let air IN to replace what the pcv is pulling OUT. If you have oil filling that tube and the air inlet tube to the throttle body, you have a problem. The pcv may be bad or there is too much blowby for the pcv to handle. Either way, that line should be clear.