MIGHTYMOUSE

iTrader: (59)

not on all catch cans.

some of them out there (or at least one) puts the pcv valve between the intake manifold and the can so that the path from valve covers to can is unobstructed and as free-flowing as possible.

any catch can using a factory pcv valve or orifice on the valve cover or inlet to can will have only the capability of flowing as much as that restriction allows.

carbuff

iTrader: (8)

Does anyone know of a generic in-line PCV valve that I can acquire, one that I could cut my existing 3/8" rubber lines and insert in the middle? I already have a catch can or I would look into purchasing the MM unit with the PCV. I've done some Googling but haven't come up with one yet...

rindoze

iTrader: (1)

Just use any check valve, I imagine this will work:
http://www.ebay.com/itm/3-8-10mm-Inline-Check-Valve-Fuel-Diesel-Gas-Liquid-Air-One-Way-Non-Return-/320985736550?hash=item4abc3da566&vxp=mtr
Also why are people running catch cans on the fresh air intake? Why not simply put a check valve like above on it.

MIGHTYMOUSE

iTrader: (59)

a pcv valve and a check valve are not the same thing, so don't expect them to do the same job. Some people use them in place of the factory pcv and find out the hard way.



people are running catch cans on the fresh air side because at wide open there is nowhere for the blowby to go except to be pushed backwards out the system, especially on boosted apps.
-the above happens stock or when any closed-type can is used on the dirty side... of course getting worse as blowby / hp goes up or with a wider piston ring gap.

JD_AMG

Ok so question for you.
What about using a one-way check valve on the clean side, and then a one way (out only) breather on the oil cap?
This way when crankcase pressure builds up it will be released through the breather (which will not allow air back in) and not blow up into the throttle body from the clean side, yet the clean side can still pass air into the crank.
Thoughts?

MIGHTYMOUSE

iTrader: (59)

you could do that, but keep in mind it would not just be redirecting crank pressure but somewhat restricting it (now that is has to pass through a check vs. none at all.

also on anything over 700 horse a single 3/8 hose is imo undersized for adequate ventilation

also you are not doing anything to catch any oil on the pcv loop so still have that problem.

JD_AMG

This is true, what are the down sides to this (other than the obvious blowing out seals)? If there is too much restriction wouldn't the oil stick blow out?
Ive been running it like this for a couple hundred miles and I think the engine runs better and feels more responsive, could all be in my head though. I definitely was getting oil/gunk coming up the clean line into my throttle body.
If this didn't work I plan on just running an additional catch can for the clean line.

Oh, Ive got a catch can for that
Engine is a very mild heads/cam 383 stroker, 433rwhp/420ft.lbs on a mustang dyno (drives really close to stock-like).
I imagine the stock PCV system (ls6 style) is adequate for this? Seems to be.

MIGHTYMOUSE

iTrader: (59)

some cars pop the dipstick, some skip straight to pushing out the rear main, which is very messy, expensive (if you don't do your own work) not to mention dangerous.

-on the 4th gens much more often to pop the dipstick.

i have what i call a 'boosted' adapter which has no cracking pressure to open, that screws into the oil fill for these applications flows more than 3/8 hose, same action that is incorporated to the top of the MM black cans.

in general at full load you see power decrease some as pressure builds in the crank. depending on power level probably barely enough to show on a wheel
dyno.

your thinking is on track. i just combine the two situations into one catch-all that can handle up to 1500 horse depending on the combo.

Cowboy97

iTrader: (3)

Ok, I've got a heads cam LS1. I've been battling the oil usage and leakage since I had it built. I put all new gm seals when the motor was done and I've only put about 8,000 miles on it in 7 years, but the leak started immediately. I've done the crank breather and tried check valves to keep oil out of the intake and in the motor, but I've never really been happy. Just recently I figured I'd come back to this thread and see if anybody had made improvements. What I've got on the car right now is I swapped my inlet and outlet lines, since more oil will go to the back of the motor on hard acceleration. I have a traditional pcv valve and an orifice pcv valve. With either one of the valves in it doesn't make enough vacuum to keep the rear main from leaking, but if I take the valves out I can hold my hand over the oil filler and feel the vacuum. However with the wide open hose will I have enough vacuum in the crankcase at WOT? I could always adjust the orifice pcv valve and set my vacuum at idle, but what is an ideal vacuum for a crankcase at idle? I might just have to breakdown and get the MM catch can, y'all have a nice looking piece.

JD_AMG

^This post got me thinking about the PCV valve too. The point of the PCV valve is to regulate flow between idle, part throttle and WOT and not let anything go back into the crankcase etc. The airflow will be different with different amount of throttle due to difference in vacuum causing the pcv valve to open/close more right? If so ->
With that being said the "old style" one is the one with the spring and stopper thing in it, while the "new" one is just a small fixed orifice hole. So how does the new one regulate flow? There is nothing to make a change in flow between idle, part throttle and WOT, and nothing to stop something from going back into the crank from a backfire or something, its just a small hole right? Why not in that case just run no PCV valve?
*To simplify things let just keep this is all for a N/A setup, as I know boosted applications are setup differently.

MIGHTYMOUSE

iTrader: (59)

buttoning things up tight to try and make vacuum is a bad idea, it will come back to haunt you in the form of crankcase pressure (which is probably the issue anyways).
the pcv system is not designed to make crankcase vacuum, its designed to bring fresh air in, get it contaminated, then consume it (for the sake of emissions and oil life). you can get some vacuum effect if you are careful but nothing to really amount to anything.

no pcv valve is way too much flow and you will put extra wear on the rings, hear air sucking past the seals to get in, and still get none of this at wide open

fixed orifice pcv 'valve' does not protect against boost.

you cannot 'vacuum' the crankcase at wide open without a vacuum pump.
you however can vacuum assist with the low pressure at the air filter (or surrounding inlet box/ tubing) if you are careful.

COSPEED2

iTrader: (7)

Not if done correctly with the proper system. IM vacuum can be the primary evacuation suction source and the area just in front of the throttle body will still have measurable suction at WOT when the IM vacuum drops to zero due to reversion pulses. You have to get above 8,000 RPM or so before the reversion pulses from a LS engine reach past the TB. And if you deal with the celanside properly, then you should never have pressure build. You wont be able to maintain vacuum like with a belt driven vacuum pump with a adjustable vacuum relief valve, but still can avoid any pressure unlike a system that vents to the atmosphere after pressure already builds enough to crack the vent valve. You can, even with a turbo or centri SC applications accomplish evacuation pull on the crankcase at all times AND retain a closed EPA compliant system.

MIGHTYMOUSE

iTrader: (59)

if you have measurable vac at the air filter then your air filter is too small and or dirty, and costing you far more hp than crank vac. could ever regain.

onesloGTO

iTrader: (2)

Ok, I'm going nuts trying to figure my pcv setup out. I drilled a hole in the metal inside portion of my round filter and installed a fitting. Ran a hose from that, which is before the turbo to the passenger valve cover.

I then have a hose coming off of the driver side valve cover going to a vented catch can. Then off the other side of the catch can I ran a hose with a one way check valve to the side of the intake manifold. With the airflow going towards the intake.

This thing smokes pretty bad. I need help please, can't figure it out .

MIGHTYMOUSE

iTrader: (59)

what 'thing' is smoking.. tailpipes? can vent?

onesloGTO

iTrader: (2)

Exhaust, catch can vent, intake.

COSPEED2

iTrader: (7)

Agreed, That is why it is critical to install secondary evacuation source as close to turbo or centri inlet as possible, The closer to the filter, the less suction due to the dismemberment.

If your venting any pressure/fumes your venting what the MAF should already have measured, and the data the PCM receives is incorrect making short term fuel trims hunt to compensate. A header evac as correctly stated above will not work with mufflers, and the best solution is a belt driven vacuum pump with a vacuum relief valve on the opposite bank as the foul vapors are evacuated from. But fresh side must be metered unless speed density tuned. And all incoming air most be accounted for with a MAF tune. A proper system should always pull vacuum/suction on the crankcase and never need to be "vented" is designed properly. It remains closed and EPA compliant, it constantly pulls the damaging compounds from the crankcase so none of the damaging byproducts are left to contaminate the oil and cause premature wear. None of this is rocket science, but so much misinformation out there it is unreal.

MIGHTYMOUSE

iTrader: (59)

it might be time for a leakdown test.

if the intake is smoking that is beyond my pay grade

Fox408

iTrader: (1)

Installed my catch can today.
Does this look right?

All I did was remove the pcv hose from the valve to the intake and run a hose from the valve to my catch can.
Then, like from catch can, into intake.

Passenger front of valve cover running straight into throttle boy.

Passenger rear of valve cover still stock running up to PCV valve.

Drivers rear valve cover, Y merged (stock) with passenger rear all the way to PCV valve.

COSPEED2

iTrader: (7)

Yes, that is correct for a NA application. You will still get oil ingestion via the cleanside (the hose that runs from the passenger side inner front of the valve cover to the TB. To prevent that get the Elite cleanside separator.