I have been doing a lot of research on different breather/catch can setups. Most people run the lines from the valve cover to the breather tank/catch can. I know you can also run lines from the back of the block to a breather tank/catch can.

What are the pros/cons of either? What if someone ran both? When are they needed and when are they not needed?

This is a kit for the back of the block



This is the typical valve cover setup

 

Feel free to post pictures of your setup as well. We can all use this as a learning tool hopefully.

 

if you look closely, the valve cover kits are also connected to the back of the block... the main reasoning of this is to catch blow by and help relieve crank case pressure...

 

See I always thought that the connections to the back of the block were there to drain oil back down into the oil pan when the car was turned off. I understand the theory of relieving crank case pressure but wouldn't it make sense to drain any oil vapors that entered into the breather case back into the oil pan?

 

the connections to the back of the block do act as a drain back when the motor is seeing vacuum...

 

Is there a downside to running just a block style one and no valve cover hook ups? Like the first picture I posted.

 

depends on the setup... there are mid 300whp cars running just the back of the block kit and they're fine... it all just depends on how much blowby/crankcase pressure you're motor is seeing...

 

I myself like the stock on a all motor set up it works fine...but as for the useing thedrain plugs as a breath is just wrong,when you take tho big plugs out and you look how the oil drains down thos it is made to back up do to the super amount of oil draining down so if you use thos plugs the oil will build up and can filll you can faster..i like the valve cover type but lol 4 is over doing it it looks dumb and is over kill..and yes there has to be a hose running to the intake that is what pulls the pressure out faster...that is why i tell rivers PLEASE PLEASE DO NOT put a autozone lil filter on the valve cover it must be in the intake tube to pull move vacumm faster..but thats me

 

so you're telling me endyn, tony1, miller of nrgtech, ect.... All of them are doing it wrong by using the back of the block? Sorry man, i think you need to look into how the setup works a little more... and we have a kit on a friends coupe, only using the back of the block, and have not filled the can once... this is on a 300+whp turbo b series car..

 

I beg to differ with regards to the vacuum effect on the valve cover. There were a few tests that I read (it might take a while for me to find them) where a vacuum gauge was inserted inline with the tube running into the intake and it actually did not pull any extra vacuum. It was always reading 0 through all the rshared_pm range. Plus if you take into account an older motor that is actually blowing oil through that rubber hose and into the intake, it will raise the heat inside the cylinders and make it more prone to detonation and can foul out spark plugs sooner.

I do not think 4 ports is overkill. Also, the ports on the back of the block are technically hooked up like stock. In a stock motor that is how they are vented.