LS venting/breather routing

[kgwmu]

What is the proper way to vent the LS engines? I started fixing some leaky seals on my valve covers and noticed that both valve cover vents are capped off. The ports on the throttle body are also capped off. Any pics would be helpful so I can make sure mine is done right. 

EDIT: Added the photos to show initial setup.

 

[Funco4JM]

You can go the route of a breather can or you can use the OEM PCV lines. It will depend on your engine and setup. 

 

[lincster]

Stock engine?

One valve cover should have a PCV valve and go back to the intake/throttle body.

The other valve cover can vent to atmosphere with a little filter on the end.

But nothing should be plugged/capped.

 

[Looney Duner]

I don't like oil mist in my intake, it's a mess when you have to take it apart, and it's really no good for the engine, builds up on the piston tops and aids detonation. 

Vent to atmosphere. Always. Routing it to the intake is simply a emissions bs deal. No benefits whatsoever. 

 

[J Alper]

Lucky capping off the Breathers sometimes will push the rear main seal out,  like above if you use the factory PCV valve and lines into the intake you will see that the intake will be soaked in oil mist, and this will also go into the motor and loose a little power, 

Adding breather lines to a Breather tank will be the route i mostly choose, 

Running a breather box can cause issues also if not done correctly, 

using 3/8 hose will slip onto the valve covers, but by using this size hose you need to make sure the hose staying taller than the motor at all points, if not it will pool oil in the hose and push it out into the box, then will see a small mess onto the breather filter, 

Larger the hose you can fit the less possible the oil will travel up the hose into the breather box, 

More breather points the better, I typically take the factory cap off and run a cap with a AN-10 fitting and also use the ones with the filters, 

I also pull out oil level sensor on the pan, or will weld a fitting on the pan for the oil that collects in the can, to drain back into the motor, 

Couple of cars, i mad a mount to hold the filter box off the back of the Head, this can be a simple way to mount a breather box 

 

[kgwmu]

The engine is an LS2 with a cam, Holley valve covers (one port on each cover) and a 90mm Fast throttle body. I'll have to grab some pics tomorrow of the current setup.

The Holley covers I have: https://www.holley.com/products/engine/valve_covers/gm_ls_engines/standard_height/parts/241-91

@J Alper, this is the type of cap you are talking about right? https://www.holley.com/products/plumbing_an_fittings_and_hose/application_specific_parts/ls_plumbing_parts/oil_system/parts/3434120ERL

Sounds like I need vent both covers to a breather box and leave the throttle body capped.  Any inexpensive breather boxes you guys recommend? 

 

[Jtmoney714]

Lucky capping off the Breathers sometimes will push the rear main seal out,  like above if you use the factory PCV valve and lines into the intake you will see that the intake will be soaked in oil mist, and this will also go into the motor and loose a little power, 

Adding breather lines to a Breather tank will be the route i mostly choose, 

Running a breather box can cause issues also if not done correctly, 

using 3/8 hose will slip onto the valve covers, but by using this size hose you need to make sure the hose staying taller than the motor at all points, if not it will pool oil in the hose and push it out into the box, then will see a small mess onto the breather filter, 

Larger the hose you can fit the less possible the oil will travel up the hose into the breather box, 

More breather points the better, I typically take the factory cap off and run a cap with a AN-10 fitting and also use the ones with the filters, 

I also pull out oil level sensor on the pan, or will weld a fitting on the pan for the oil that collects in the can, to drain back into the motor, 

Couple of cars, i mad a mount to hold the filter box off the back of the Head, this can be a simple way to mount a breather box 

Can you post some pics of the different set ups you e done please. 

 

[J Alper]

The engine is an LS2 with a cam, Holley valve covers (one port on each cover) and a 90mm Fast throttle body. I'll have to grab some pics tomorrow of the current setup.

The Holley covers I have: https://www.holley.com/products/engine/valve_covers/gm_ls_engines/standard_height/parts/241-91

@J Alper, this is the type of cap you are talking about right? https://www.holley.com/products/plumbing_an_fittings_and_hose/application_specific_parts/ls_plumbing_parts/oil_system/parts/3434120ERL

Sounds like I need vent both covers to a breather box and leave the throttle body capped.  Any inexpensive breather boxes do you guys recommend? 

The Latest Rage is a really big and nice breather box, 

Yes the cap you listed is perfect, 

The motor is like a Air Compressor, the rings need to have a gap in them for expansion when the motor heats up, but the gaps never fully close, so the burn cycle in the piston will blow by the rings,  this will create pressure in the block, so the more venting you have the less likely any pressure will build up, 

Latest Rage Breather Box, styles 

 

[J Alper]

also if you run 3/8 to the valve covers, on the push-on barb on the cover, you can also put the other end to 6AN pushlock on the box, so you can do 6an from the covers and 10an from the cap, 

you can use this for a drain back also, 

LS Low Oil Level Sensor Plug w/ 1/8 NPT Port (speedwaymotors.com)

 

[Pennywise]

this is the one I'm planning to use 

https://www.motionraceworks.com/products/motion-raceworks-billet-dual-port-catch-can-dual-10-an?variant=31066317029516

 

[kgwmu]

this is the one I'm planning to use 

https://www.motionraceworks.com/products/motion-raceworks-billet-dual-port-catch-can-dual-10-an?variant=31066317029516

That is a nice looking piece! 

 

[kgwmu]

added pics of what I have now in the first post. I think I understand what I need to do for the valve covers, now another venting question.

Where should these be routed? The one on the left is connected to a port on my radiator and the one on the right is connected to an oil catch can that just has a hose running to atmosphere.

 

[Jtmoney714]

also if you run 3/8 to the valve covers, on the push-on barb on the cover, you can also put the other end to 6AN pushlock on the box, so you can do 6an from the covers and 10an from the cap, 

you can use this for a drain back also, 

LS Low Oil Level Sensor Plug w/ 1/8 NPT Port (speedwaymotors.com)

So run 3 hoses to the catch can and then one drain back to the oil pan? So would you need a catch can with 4 ports?

 

[wesinls]

added pics of what I have now in the first post. I think I understand what I need to do for the valve covers, now another venting question.

Where should these be routed? The one on the left is connected to a port on my radiator and the one on the right is connected to an oil catch can that just has a hose running to atmosphere.

View attachment 41906

That should be reversed? Meaning, the one on the left should go to oil catch can and one on right is your steam vent and should go to the radiator.

 

[J Alper]

So run 3 hoses to the catch can and then one drain back to the oil pan? So would you need a catch can with 4 ports?

you can weld another one in that would be best, or T off the bottom is good, if you have the center breather, that is one of the best the LS did, it has a oil Air separator baffle built in, so if you have the 2 valve covers and the center, most likely you do not need the filler cap to have one also, the bigger the cubes of the motor the more breather i would want,