Hey everyone,

So bit of a weird situation. I am building a stroker LQ4 with an LS3 top end. The valve covers I purchased were off of a guy on kijiji, and they are off an DR525 crate engine. The driver side valve cover has two threaded holes that I assume are for hooking into a PCV / catch can system, and the passenger side has the oil fill cap and the fresh air intake breather from the intake like a regular LS3 valve cover would have. I have red a few different threads and I think I understand the purpose, but I am not sure if I should just plug the 2nd hole on the front of the driver valve cover or not...

Does anybody know how I should be properly plumbing a catch can / PCV system in and if so, does anybody have any recommendations for which brand for catch cans installs. I want something with a valve in it, not a cheap system, but not stupid expensive either.

Thanks everyone

 

Mighty mouse catch can. His come with good instructions and he returns emails fast. I bought mine from the ws6 store. The fittings are modular so you can increase hose size depending on your hp. He has a few different setups, i have the integrated pcv valve in mine, but they are all on his website.

 

^ thanks burnt!
We have those here
http://www.ws6project.com/user_stor/catalog/product_info.php?cPath=235_87_389_505&products_id= 6352

 

Ok, but would the plumbing be the same as a regular system? Thanks for the recommendation by the way!

 

Yes they are thw same

 

If your running a PCV system run dual catch cans! One from the valley cover through the first catch can and into the intake manifold port. Cap off the drivers side valve cover and run from the passenger valve cover port through the second catch can and then into the throttle body port or the air intake tube between the MAF sensor and the throttle body.

 

If you are going to run a dual catch can and decide to cap off the driver cover then you are defeating the purpose.

 

The purpose of the cans are to keep oil from entering the intake but it still gets there and if you want to add another way for oil vapor in then by all means GO FOR IT!

 

If you do not have a valley cover with a PCV built in then run the driver side valve cover to an inline PCV before the catch can and then into the intake port. Leave passenger side as previously mentioned. The LS2 platform in the GTO has the driver side capped off, PCV valley cover to intake by way of hose, passenger valve cover connected to the throttle body.

 

The purpose of both valve covers having the ports is for pcv. The engine basically has 3 bays. without the vented valley you only have 2 ways from pass and driver.
In vented valley setups, the valley tube goes to the side of the intake and the pass valve cover goes to the "clean air" or port before or at the tb. If you have a dual catch can then you can not only run the valley to the can then to the intake but you can T both valve covers together and vent both the other areas and run them to the catch can. Keeping the driver capped only allows the pressure to build there as well. If you have the chance to vent all 3, why would you not?

 

Imagine the crankcase is like a cup with a lid. You put one hole in the lid for the straw, thats where the engine's intake manifold sucks from. When you pull on the straw, how does air get back into the cup to replace whatever mass you removed from the cup? In a real cup, the air flows back in through tiny crevices, around the straw, around the lid, anywhere it can fit. In an engine you don't want those crevices because they are oil leaks. Instead, you put a second hole in the cup somewhere, so that whatever is removed by the straw can be replaced. That is the hole connected to the pre-intake manifold, post air filter side of the engine. It is post air filter because the air filter has cleaned the air. It is pre-intake manifold because that side is where pressure is atmospheric. Thus, the intake sucks on the straw, the other hole feeds from the atmosphere replacing what was lost.

Now examine the holes in the cup with more detail. What you want to pull out of the cup isn't liquid; in fact we only want to pull air (gas) from the cup, not liquid or solid material. Thus the straw must be "shrouded" or "baffled" to protect it from the liquid in the cup. The same goes for the other hole, it should not leak out or in any liquid.

If the baffle is poor, liquid passes into the straw. that means the intake manifold sucks up liquid oil. The baffle should never allow oil to pass through into the straw; this is a design flaw, or a mis-use (unintended use) of the straw. The real fix is to improve the baffle so the straw doesn't pick up any liquid oil. A BANDAID for this problem, if you do not or cannot easily fix the baffle for the straw, is to use a "catch can". The catch can simply gives you a "secondary crank case" or an additional cup with which to store oil and further try to baffle the straw.

 

The catch can doesnt bandaid the pressure made in the crankcase. The catch can only filters it when it is excessive. If the pcv system operates properly and there is little to no blowby then you wont have as big an issue with oil mist and need a catch can. There will always be windage in the crankcase as well as vacuum and pressure. The pcv system is designed to alleviate that pressure. If you capped all of it off, youd have issues like an sbc used to have...blowing the dipstick out of the tube or blowing oil past seals etc. Blowby issues, improper machining, rings not working properly, low tension oil rings, larger than necessary ring gaps all of those are the issues that agitate the oil mist/consumption issues.

 

what do you call it when an engine produces/leaks liquid oil externally beyond an expected factory limitation/expectation, and then we, the end user, add a device to temporarily control the issue which should not be present to begin with?

A band-aid is a term of endearment as if the oil were blood. You can call it a filter, or a 5-gallon bucket, or a place to dump liquid that spews forth. I don't care. But do not pretend that it isn't an "additional piece of what should be unnecessary equipment that covers a cut/bleeding orifice".

 

I didn't say that at all, what i gave was an example of either an improperly working or capped off pcv system. I said it wasnt a bandaid for the pressure because the pressure differential will always exist. It is a bandaid for the issue when exxessive blowby or even windage exists.

 

LOL@ a catch can becoming such a debate. They are certainly not detrimental, so why not have one. If a motor has way too much blow by than it is on the way out anyhow.

 

The reason it is such a debate is due in part to all the videos and builds using jy engines and then maybe turbos. They just think that all ls engines need a catch can so they put one on and run, when in fact they just want to dodge the real problem and do not want to spend any extra money.
Any engine used enging i purchase personally gets completely refreshed. Sometimes ill buy a pretty banged up engine for cheap because im going to in fact rebuild the whole thing.

 

Recap
Kingtal0n: Catch can is a place to store oil that leaves the crankcase, to bandaid (stop the blood flow) due to a poor/misused baffle which cannot currently be fixed. --> (doesn't mention pressure, just blood)

WS6store: The catch can doesn't bandaid pressure, pressure always exists.

Kingtal0n: ?? I didn't say it band-aids pressure, how is that even possible to stop/trap pressure or airflow with an open tube?


Weeeeeeeeeel. Yes and no. Yes because sure, it probably is negligible on some applications. No because, anytime you increase the volume of the crankcase, you disturb the pressure differential (now we are talking pressure). In other words, double the size of your crankcase, and now the vacuum signal provided by the intake manifold during cruise/part throttle is diminished significantly (less PCV action). Every hose & catch can you add is additional volume that reduces the effectiveness of the PCV system. If we all start adding catch cans (volume) for no good reason it may have long term consequences for our engine's health (oil quality, economy, ring condition).

 

Your analogies of a straw in a lid and bleeding are far off what goes on inside an engine or in how the pcv actually operates.

The catch can doesnt add air to the system. Do you have any idea how fast air pressure moves inside or even outside an engine? Why does gm put pcv tubes into the air stream before the tb? And again why is there one after? Its a simple balance.
Adding a catch can does not change the vacuum signal at idle. If you had an oil cap breather it would, but that is dependend upon the size of the possible unmetered air going in. There are offsets in factory computers for the airflow caused by egr and other things as well.

 

Engines wear. what happens when they do?
The only way an engine would blow oil out of seals is if the pcv system is not operating correctly just like i said.

The other reason i remarked that you skimmed over showed that as well.

What would you recommend every time you find oil in your pcv system? Not using a filter to keep oil consumption to a min and not cause other issues like knock etc? Because a catch can is a filter whether you wish to admit that or not and it does help in those situations.

 

So here's the million dollar question.

Why even put the vapor/mist call it filtered air if you want back into the intake to be reignited? This so called filtered air which is really a smoke by the way does have oil deposits in it and will without doubt coat your valves, pistons, injectors, and eventually clog the intake manifold and catalyst over time causing your engine to LOSE POWER!

Your octane points are even lessened due to that filtered air/smoke mixing with your air/fuel mixture. No doubt sealed catch cans will get some of it but it's not stopping all that smoke from making its way back into your engine and exit out the exhaust!