LS postive crankcase pressure, pcv, catch can?! Help!

[12ftgso480]

Gen 3 6.0 with truck intake. I'm getting lost and learning catch cans are a thing. Spoke with my tuner and he suggest positive crank case pressure no catch can? Can we please post some pictures and have a discussion here? Pretty sure my setup in pictures caused my dipstick to push out and possibly blew a crank pully seal in one test hit. Thanks in advance !

 

[12ftgso480]

Somebody ? Anybody?

 

[EastBay]

Hello,
I run catch cans on both sides on my Ecoboost 3.5L Ford pickup trucks....its amazing all the sludge they catch. Cannot say what the application is for a LS motor.

 

[Slidin Gator]

While not the cause of your issue, these two hose barbs need to be connected. Double check, but the hose barb on the throttle body should route to a location upstream of the throttle. This is the side that allows filtered air from the air cleaner to enter the STBD front valve cover.






This is the side where vacuum from the top of the intake manifold draws out the gases from the PORT side Stern. This is the hose where any catch can would go into.

 

[Slidin Gator]

My LS3 has the same setup. There is no PVC valve in the circuit, just an orifice in the valve cover connection. Basically it is supposed to be a fixed intake vacuum leak that the efi is tuned for. Like any vacuum leaks, it is strongest at idle with minimum vacuum at WOT.

Pull the hoses off and blow/suck each direction. It should be an open hole into the top of the intake manifold and into the throttle body barb to in front of the throttle plate (air filter side). Going the other way, there is an orifice in the port on each valve cover. You should be able to blow into the port, but you should feel some restriction. If too much restriction it might be clogged with oil/carbon.

As for the catch can, it goes in the PORT Stern line to stop oil from entering the intake manifold and dirtying up the intake and intake valves. You may want to install a catch can at some point in the future, but it has nothing to do with your case pressure issues.

 

[Slidin Gator]

So what is the cause? From the way you have it plumbed right now, unless the valve cover ports are clogged up, the only other reason I come up with for high case pressure it too much blow by. My next step would be a leak down test to confirm all is well after the break in runs.

 

[One Eyed Gator]

As for setup mine is a little different.
Pic 1 Valve cover goes to my catch can. throttle body in capped (silicon cap)
Pic 2 hose comes off valve cover loops down with small filter upside down and a safety wire
Made a bracket of the rear of the head

May not be right but has worked for several years without issue
Rather not have oil reintroduced in the intake

High case pressure may very well be something else

 

[12ftgso480]

So what is the cause? From the way you have it plumbed right now, unless the valve cover ports are clogged up, the only other reason I come up with for high case pressure it too much blow by. My next step would be a leak down test to confirm all is well after the break in runs.

So valve cover in picture 1 I had taped up and honestly had forgotten about it. I would not think that would cause that much crank pressure but still new to the game. I've got in contact with few locals with catch cans. I will keep yall posted on the final decision. I had a hard time finding much info on the subject

 

[Slidin Gator]

So valve cover in picture 1 I had taped up and honestly had forgotten about it. I would not think that would cause that much crank pressure but still new to the game. I've got in contact with few locals with catch cans. I will keep yall posted on the final decision. I had a hard time finding much info on the subject

So your system was sucking against tape and the result was stuff blowing out? Makes sense that it may need both valve cover's open to atmosphere for full breathing.

Reminder, still building my first here. Haven't lit mine up just yet. I completely agree that the info on the LS PCV circuit is hard to come by.

I'm using the OEM L92 intake and valve covers. The PCV hose is the OEM setup. The Port side is my tip off on the system. The port side valve cover connects directly to the intake manifold. This has to be the suction side. This is also where I would expect oil to come from. If I was going to put a catch can it would be in this line to keep the intake from sucking oil out of the Port side valve cover.




So then I put the bigmouth throttle body on and it has a 3/8 hose barb that feeds directly upstream of the throttle. This is where the breathing comes in.

 

[Slidin Gator]

The #1 requirement of any crankcase breathing is the ability to vent pressure spikes, positive or vacuum. The PCV circuit biases everything to vacuum (boosted setups not included) and draws moisture out of the engine at heat up. You want to feed that vacuum clean air.

Delete the tape and connect the STBD valve cover to the air filter per original pic #1 so the system sucks in filtered air. I would still run an 8x leak down to make sure all is good before the next round of "Tuning".

 

[12ftgso480]

So we're convinced the Barb on our throttle body is the clean air side ? If we were gonna run a catch can we would get rid of the pcv and run that to a catch can ?

 

[Slidin Gator]

The clean air comes from the air filter, some where in front of the throttle plate. Take an air hose and blow into the barbs on the throttle body and make sure they flow to some port on the air filter side of the throttle plate. If the port connects to the intake manifold (vacuum side of throttle plate), then it is not correct. My aftermarket throttle body has a connection specifically for this purpose, your OEM throttle body may not (hose originally routed to air filter plumbing)

You need a filter of some kind on the STBD FWD valve cover barb, either the main air filter or a separate filter. This is where fresh air enters.

The catch can would go in the line you presently have running from the PORT STERN valve cover to the top of the intake manifold. You keep the connections at the valve cover and intake, just add the catch can in line.

1 Eye Gator just reverses the connections and flow of air through the engine, same result. Filtered ambient air coming in on one side and out the other side, powered by intake manifold vacuum.

 

[Slidin Gator]

My system is presently plumbed like this diagram, except without the catch can. Note that only the PORT STERN valve cover is supposed to have an orifice in it. The STBD side is where high case pressure pushes back to. Since that was taped up I would say that was the likely cause of the high case pressure. Must be good tape!

Lots of catch can options, follow the instructions. Keep in mind that the purpose is to prevent oil from entering the intake. Catch cans don't improve crankcase breathing.

PCV/Catch Can routing for LS3/L92 C5 - CorvetteForum - Chevrolet Corvette Forum Discussion

In the picture below, the dirty side is flowing into a port on the intake manifold side of the system. The truck intakes have this port at the top of the intake manifold where you are connected in original Pic #2.

 

[12ftgso480]

My system is presently plumbed like this diagram, except without the catch can. Note that only the PORT STERN valve cover is supposed to have an orifice in it. The STBD side is where high case pressure pushes back to. Since that was taped up I would say that was the likely cause of the high case pressure. Must be good tape!

Lots of catch can options, follow the instructions. Keep in mind that the purpose is to prevent oil from entering the intake. Catch cans don't improve crankcase breathing.

PCV/Catch Can routing for LS3/L92 C5 - CorvetteForum - Chevrolet Corvette Forum Discussion

In the picture below, the dirty side is flowing into a port on the intake manifold side of the system. The truck intakes have this port at the top of the intake manifold where you are connected in original Pic #2.

Right on gator! I got a set of leak down guages. If all is good guess I'll try to hook everything up to have "positive" crank case pressure and see if we do good. If not I may just vent all to catch can if we're still building pressure.

 

[12ftgso480]

I never did do a fallow up with my pressure issue? I ended up venting everything to a catch can. Have been out atleast a dozen trips and have not ran into issues thus far.