I'm adding a catch can to my 1990 740 Turbo. I've also decided to use a vented valve cover as the engine creates a lot of blowby under boost.

Can I simply use a T or Y shaped barb fitting to connect the hoses from the standard breather box and the valve cover vent to the catch can? Will this cause any issues?
Is it venting because the breather box is blocked? I ran mine straight into a catch can then onto the intake and its doing well.
I haven't installed the vented valve cover yet. I'll inspect and clean the breather box when changing the hoses, however it was replaced about 65,000km ago and seems to be operating correctly.

I'm assuming running the valve cover vent and the stock breather box to the same catch can won't cause any problems, but I'd like hear from someone who has ran this setup.
Vented valve cover won't fit on a B230 head.

The rally car ran a vented cover into a catch can, and the stock block-mounted breather into the same catch can. No hassles with it.
Cheers Spac, that's what I wanted to hear. It's not a factory B21/B23 vented valve cover, it's a B230 one with a fitting attached. I think it's from Ash's 240.
Let me know if you need any AN fittings too.
On this, I fitted a 140 breather/oil filler cap to the gt & tee'd it into the existing breather line & it proceeded to pump lots of oil into the intake on high boost so don't do that!
i used a fitting on the blockoff plate for the mechanical fuel pump. much neater solution as its low down and not visible.
@Vee_Que you know mine. kinda like yours but with a large venting catch can.
i get a lot of shit out the catch can filter though. and venting to atmosphere. is not entirely legal
Mine also goes back into the air intake. Will take pics next time I'm working on the car.
4 months later
I removed the valve cover breather hose yesterday. After my daily commute I got 30mL out of the catch can, compared to an average of about 250mL with it attached.
250ml!!? That doesn't seem right.
Even 30ml seems high. Although after just that commute, or longer time frame?
After my 60km round trip commute. The engine is very worn out and runs 15psi boost, so 30mL sounds pretty normal.
Hm. I might disconnect my breather pipe then too.
5 days later
It's been behaving itself again now, with around 40mL coming out of the catch can after 200km of driving.
Where does the drain normally go? Not back into sump?
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