A refresher course on the importance of your PCV system:

[RevXtreme 1]

Heres the problem with hoses hanging near the ground & plugging your vacuum source. When at speed, one hose will develop negative pressure, and the other positive as the hose has a venturi effect when air is moving past it. What happens then is you are sucking up dirt, sand, water, etc. directly into your valve cover & into the motor internals. I suspect they have no filter on them, correct? Also, if you are not pulling metered vacuum at idle & low RPM's the harmfull vapors that are in your crankcase cannot be pulled totally out...only pressure vents so all the unburnt fuel, caustic gasses from blow-by, & moisture will re-condense in your crankcase after the motor cools & contaminate the oil as well as corode internal parts (look at the links in another thread on bearings & see the damage just the unfiltered dust causes). A proper PCV system needs a fresh air source that is filtered, (on the stock OEM setup it is drawn from in front of the throttle body & the main air filer cleans the air pulled) and a vacum source that is metered & valved, such as the PCV valve on a LS1 or the fixed orfice & baffle system in the vally cover of the LS6 & LS2/3/7 design. The problem with the OEM systems on our vettes is it allows oil vapors to be pulled into the intake & robs power & contributes to detonation. The only proper way to correct this w/out sacrificing your engine to premature wear (I have seen motor come in that look like dirt was poured right into the crankcase & no internal part not showing advanced wear & failure from the hoses dangling unfiltered to the ground. Those that have this setup just have to look closly at your oil the next time you change it to see how dark it now comes out compared to when you had the stock system in place) is to modify the system to remove as much of the oil & harmful vapors from the PCV lines before the mist is pulled into the intake. So the most effective mod for NA motors is to add the proper catch can system AND a PCV valve inline to control the amount of vacuum pulled & prevent back-flow of the vapors.


The catch can must be of a material that disipates heat effectively, and that eliminates plastic. Auminum or steel are the 2 best. 2nd, the can must be baffeled in such a way as it disperses the vapors to make contact with as much of the cooler outer surface of the can to allow the vapors & oil to condense into droplets that are collected in the bottom of the can. Now 2 forms of oil come through the system....a mist from the fast movong internals in the engine which is pretty easy to trap, and the vapors from the high heat which need the cooler surface area to condense.
So the can has to be large enough to be effective & most I see in use are far to small, allthough there are several good ones on the market. Then the outlet of the can must be located as far up & away from the inlet to prevent vapors from being pulled through before having a chance to cool & condense. You then need a PCV valve to control the amount of vacuum.






(this setup uses a perforated down tube to disperse the vapors as completly as possible for contact on the cooler surface & is a 1 qt capacity)


If you have a stroker, big cube build, or run at extended high RPMs you should also add the filtered breather as some have mentioned above (easiest is as an oil fill cap mod) and this will allow a good volume of filtered fresh air in at low RPMs and allow venting of crancase pressure at high RPMs. On a FI application it gets just a little more complicated but the design is very similar.

Shown below is on a Magnacharger application.




So what you have accomplished is a near total elimination of any oil getting into the intake, proper ventalation & breathing, and not subjecting your babies motor to a slow horrible premature death from unfiltered ventalation.

Hope this helps.

For pages of Q&A on the subjet please go to:http://www.ls1tech.com/forums/genera...ging-down.html

[navy2kcoupe]

Nice write up! Helps me to understand what's going on with and inside my motor as it relates to the PCV system. Thanks guys!
Andy (UNITS)

[Rich Z]

Interesting stuff.....

How much of an issue is something like this on a car that is driven on the street at legal (or nearly so) speeds? I would think that if a LOT of oil (via misting by the rotating engine components) were being circulated into the cylinders via the PVC system, then I would be seeing substantial oil loss from the crankcase, needing to have the oil level topped off periodically. But I don't see that at all. I've never had to add a drop of oil between oil changes.

So it this an issue strictly for cars that are driven VERY spiritedly?

Or am I just not understanding the issue at all?

[RevXtreme 1]

Originally Posted by Rich Z

Interesting stuff.....

How much of an issue is something like this on a car that is driven on the street at legal (or nearly so) speeds? I would think that if a LOT of oil (via misting by the rotating engine components) were being circulated into the cylinders via the PVC system, then I would be seeing substantial oil loss from the crankcase, needing to have the oil level topped off periodically. But I don't see that at all. I've never had to add a drop of oil between oil changes.

So it this an issue strictly for cars that are driven VERY spiritedly?

Or am I just not understanding the issue at all?

Average street driven car should use no more than a pint or so through the PCV system in 3-5k miles. The issue is with the closed PCV systems required now days to meet EPA standards coupled with the added cost & 1 more step (that customers hate) in maintaince result it manufacturers tolerating the small usage and then the service departments can make more $$ doing de-carbonization treatments later down the road is why you don't see effective oil seperating devices on todays cars. A can means one more item to drain at service intervals.

All you need to do to see if you have an issue is to remove your throttle body, take a clean towel or white paper towel & stick it into the intake snout as far as you can and rub it around. If no oil comes out on the towel you have no need for an improved set-up.....the small amount pulled in will only result in normal carbon buildup over time. If you do have oil on the towel, you are pulling in enough to not only reduce the amount of energy released with each explosion (you only want fuel & air in the combustion chamber....any oil contamination causes an erratic burn, detonation, and less power).....but the by-product is carbon build-up on the piston tops resulting in a rough surface that does not allow for even flame & will result in hot spots in the carbon layer. It also builds up on the valves and decreases volumetric efficiency, or velocity of the flow into & out of the combustion chamber.

If you are using enough oil to top off between changes you most likly have a more serious issue that a oil seperating can will not fix, only band-aid it. (worn rings, bore, guides, seals, etc.)

Now on a forced induction setup you need a more complex design that integrates several one-way check valves so that at idle & no/low boost operation the vacume from your OEM source (intake manifold snout) pulls the vapors out....but under boost the valves shut down any back-flow or reversion and a feed from the cold air side of the head unit provides the vac for flushing the crankcase.