Just got an A&A Si Trim installed, had an existing Elite E2X Dual port catch can which the shop hooked up just as I would have done myself combining the E2X and the A&A instructions.

Someone pointed out concern with my routing due to the drivers valve cover going directly to the inlet of the blower and not going through the catch can saying I'm sucking dirty air right to the blower. Below is my current configuration which is the A&A recommended routing but with one of the catch can outlets T'd in.


He suggested running the drivers valve cover into the line coming from the valley so that both would run into the catch can like so.



I'm confused on either being used as an evacuation point as everything I knew previously was that this line was part of the "Clean side" for drawing in metered air to the valve cover and the evacuation came from the valley cover but every setup I see tends to use the drivers valley cover as part of the dirty side.

When I talked to Elite they suggested that both valve covers should be joined like so.


My head is spinning trying to figure out what the "Proper" way to have this setup is to maintain the closed system but be able to properly evacuate with as little junk going through the blower.

Input... tech discussion... etc.. all welcome. lol.

 

There is nothing wrong with one of the valve covers venting right back into the intlet of the blower. **** the stock airbox does this.

Totally typical of ALL basic centri kits.

 

Just trying to understand if there’s a better way to do it or if I should just leave it how it’s plumbed in the first pic.

I wasn’t sure what the affect of pulling that much vacuum on the drivers valve cover is as I’ve seen that connection labeled as fresh air IN not dirty air out and running right to the blower inlet is going to pull a lot harder then the factory setup. There’s so much conflicting info out it makes my head spin lol.

Best pic I have of current routing which is reflected in first paint diagram.

 

I agree. This topic has been beat to death. If you followed A&As install it is fine. Don't sweat it.

**** I just run a breather system that connects no where to vacuum lol.

 

the bottom line is that you are not sucking oil into the front of the blower, or pressure building to the point of pushing oil past the main seals or dipstick popping out.

but for sure you cannot do the middle drawing. the valley plate fitting is the pcv control point which you are defeating by tying the driver line into it.

 

I'm just trying to understand the proper function of the drivers side valve cover fitting. I see some saying it's dirty side and applying vacuum to it (Stock A&A and my current setup)... using it as a vent (Your setup, LMR etc.)... others saying it's clean side air in (3rd drawing)... Not sure what the actual function is... what is "proper".

 

gm has changed their purpose for that fitting 3 times on c7 dry sump, so is not an easy one to answer. tadge always seems to have a great 'we meant to do that' approach lol.

trying to control the oil is not easy, but if you get control of the air, you also get control of the oil.

to simplify all that is going on just think of them as passages to the crankcase

one of which, will have a pcv valve, and it must connect to the intake manifold with a dedicated line

one of which needs to connect to open fresh air, preferably metered (this is dry sump forward port)

then there are the lines to and from the oil tank, which are to participate in the pcv system as well as maintain air balance above the oil within the system as a whole

some cans defeat the pcv
some cans go direct in line of it
some are a mix of using pcv and giving auxiliary method of crank flow control with additional line or vent point

none of this directly answer your question, but once you understand the job that needs to be done, the layout comes naturally following.

clean air in, dirty air out, blowby out

 

So basically there’s nothing “bad” about my current setup in picture 1 except that the catch can is only catching what comes from the valley cover and “dirty” air can still come from the drivers valve cover into the blower leaving the dry sump tank and the passenger valve cover as the only fresh air source since the drivers side valve cover will always be under vacuum

Picture 3 basically duplicates the PCV changes GM has made in 2017+ in linking both valve covers to a fresh air source from the dry sump tank and using the valley cover as the single evacuation point which is filtered through the catch can and uses the blower inlet as a vacuum source for when the intake manifold is under Boost.

 

agreed. if you have no symptoms of crankcase overpressure with the last pic, it has the best chance of overall oil-free operation, given that hardware selection