Vented catch can or closed catch can

[70chall440]

I am trying to decide how to configure the breathers on my Cuda, originally I was going to build the system like they used on the race cars (one hose/tube from one valve cover to the other with 2 breathers in the middle) however I have determined this isnt what I want. The problem is that I have -20 male AN fittings on each cover. I have tried to find a short breather but as of yet haven't. I am now thinking of going to a catch can type arrangement but I have discovered there are many different types/styles. I did some internet searching and have yet to find a reason to favor one or the other. My initial thought is that i should use one with a filter on it as it needs access to vent/breath but now I am not too sure. I do have a standard PCV on one (left) valve cover however.

[70chall440]

I have been doing a lot of research on this subject as there is a lot of information online. I have determined that that there are a variety systems that can be used. Originally all of the factory made cars ran a PCV valve on one side and a breather on the other. The PCV valve connects to the intake and the breather to the air cleaner. Before someone jumps on me, the previous system to the one I just described was a draft tube which dumped onto the ground. This is generally called an open system due to the fact that the blow by/pressure is vented to the atmosphere.

Performance engines use (or should use) a different system than the one described above to reduce oil mist from entering the carb, throttle body or in some cases the plenum as it reduces the quality of the fuel/air charge and thus reduces performance. that said, an internally combustion engine needs a ventilation system to reduce/eliminate internal pressure. This is where the confusion comes in; there appears to be several systems in active use; an unvented closed system and a vented closed system. I personally remain unsure which is a better system or perhaps I am not completely understanding them, but it seems that vented system would be more functional.

I am attaching some pictures hopefully to start a conversation. As it relates to my engine, ascetically I would prefer to just run a breather on each valve cover (mainly because I have -20 male AN fittings welded on each), however I am beginning to think that this might lead to oil mist on the cover and intake. My next option would be to build a vented closed system; down side to this is the additional hoses but I guess I can live with them.

I am very open to a discussion on this.

[73440]

https://scholar.uwindsor.ca/cgi/viewcontent.cgi?referer=http://r.duckduckgo.com/&httpsredir=1&article=6217&context=etd

Is an oil seperator going to be part of your system ?

I read thru his thesis , it seemed thorough , by my limited knowledge of the venting  system and needs.

[70chall440]

Thats what I am trying to decide. I really dont want to put another tank in the car but I might have to.

Thanks for the link, I will read through it.

['Cuda Hunter]

That's a lot of reading.
I have nothing but opinion so I'm just watching the thread to better understand the situation.
 

[70chall440]

Yes it is a lot of reading, I got through about 1/3rd of it.... What I have been about to ascertain is there are a number of issues at play here that tend to convolute the overall issue making it difficult to get your head around. Here are the "base" issues;

1. the engine produces internal pressure which has negative effects on the engine
2. the pressure must be mitigated in some fashion

Here are my observations thus far (not saying they are right)
- The factory system is adequate for most applications/instances; however it must be used as it was designed.
- forced induction requires more/better pressure control because it produces more pressure
- modern cars seem to use completely closed systems; especially turbo cars
- the term "closed systems" appears to be misleading as there is a vented closed system and unvented closed system
- there is actually 2 systems; one that uses a PCV system ad one that does not; in other words
---------one system (PCV) recirculates unburned fuel (and oil) through the intake and air cleaner
=====one system vents its pressure through a catch can or oil/air seperator (more on these in a sec) and either vents it to the atmosphere or returns it to the intake (usually on the charge tube running from the turbo to the throttle body)
- a oil/air separator is a catch can but a catch can is not a oil/air separator.... meaning a air/oil separator has a design that actively removes oil from the air before the air is vented or returned to the engine whereas a catch can allows oil to collect somewhat naturally (as in due to gravity more so than screens and baffles)

So what does all this mean or better said, what to do? Well from what I have determined it comes down to this
- the stock PCV system is adequate in most cases, however it does return "dirty" air back into the engine (good for emissions, bad for internal sludge and in some cases performance)
- you can install vents (filters) on the valve covers and vent to the atmosphere (without a PCV valve), however you will probably experience some oil mist accumulating on the engine depending on the filter, the engine, how hard it is used, etc.
- you can run lines from each valve cover to a vented catch can or oil/air separator (without a PCV valve) and accomplish the task without putting dirty air back into the engine and reducing or eliminating the oil mist problem

As for me, I have ordered a cheap vented catch can off eBay and will see if I can find a place to out it, however I am also still looking for a short filter that has a 1.250" clamp on inlet (I have 2 K&N filters but they are 3" tall) and I may try an open system (a filter on each VC w/o a PCV valve) and see what happens.

[734406pk]

Interesting topic! I was wondering about this myself. The existing Mopar PCV system design does work to control crankcase pressure but having the oil mist etc. being drawn into the intake has several negative results. For one, the vapors are just like the engine is ingesting low octane fuel (detonation)and second, the intake deposits that form rob power even further (so much for port/polish). What seems best for the engine is to not allow these vapors to enter the intake air stream at all and vent them externally. The common drag race style "header dump" system makes sense but the exhaust back pressure on a muffler equipped engine must be low enough for it to work properly. Just my   

[70chall440]

I believe you are on the "money" with your theories. I think a vented catch can or perhaps even better a true oil/air separator system would be the best choice for a NA street mild strip engine. The oil/air separator system when connected back to the PCV inlet allows the air to be recirculated without the oil although I would agree that the quality of that air isnt probably very good.

As I mentioned, I am going with an open system for now, if it gets oily then I will go to a catch can or a oil/air separator (a real separator system is far more expensive than most you see on eBay which are just basically a catch can with screens).

[734406pk]

Here is an example of a commercially available oil/vapor separator, regularly used in my line of work. Although it's one of the smallest units made, it's still rather large for an E body engine compartment. Food for thought anyway... Good luck with your crankcase vent system!

https://www.parker.com/literature/Racor/55395_Rev_B_CCV3500_Series.pdf

[70chall440]

Pretty cool, dont think it would look all that cool inside the engine compartment but I am sure it would work.

[734406pk]

  Still too big for our use, but the design does work. Someday there may be a scaled down version available for us. Also it's worth mentioning that if/when you eliminate the factory PCV system and go with an open breather, carb rejettng/tuning will be necessary- unless you are running a self-tuning EFI. The vacuum leakage from the PCV is incorporated into the fixed jet carburetors. Without this leakage the engine will go rich.

[jimynick]

My son Nick is right now working on a similar set up and has gone with 10AN fittings, one in each valve cover linked by braided 10AN hose back to a T which picks up the lifter valley vent and they come over to a dual-spigotted/vented and baffled Proform catch can mounted on the rt inr fender. The car is mechanically blown and blowby was an issue causing oil leaks hither and thither. We hope this helps to alleviate some of that. 

[70chall440]

That seems to be pretty common with blown motors.

[73440]

I think you are on the right track keeping everything out of the intake, keep clean fuel there.
I didnt read every word but skimmed thru it all and came away with some more understanding of the system.

[70chall440]