North American Turbocoupe Organization

Valve Cover Breather
John B Offline
So, I've owned my 88 for a little over a year now and as much work as I've done to it, I'm still discovering new things about these cars everyday. The previous owner replaced the valve cover breather with a simple K&N filter to vent to atmosphere. On my previous car (04 focus ZX3), I also vented the valve cover to atmosphere when I turboed the car. I've been reading through some forums and it seems that this set-up could create a vacuum leak since the air is not vented/routed back into the intake before the turbo/after the VAM. I've driven my 88 like this since the day I got it and haven't noticed any drivability issues. There's an occasional hard start after the engine has been running for some time but I don't know if this is even related. I want to replace the valve cover filter because 1) it's gummed up; as expected and 2) I rather not vent directly over my valve cover. Should I route the VC vent back into the air intake (pre turbo/post VAM) or keep the vented to atmosphere set-up? FYI, The oil-separator and PCV on the driver side is the stock set-up with the hose running to the upper intake. At some point, all this will be replaced with a catch can set-up and deletion of the VAM but for now, I'd like to know which would be the best way of going about this. Thanks!
88 Turbo Coupe: Front mount intercooler, MGW short throw shifter, full coilover conversion, tubular control arms front and rear, svo front brakes, vacuum assist brake swap, manual steering swap, GT35R turbo with external gate, pimpx ecu, 60lb injectors, 3 core aluminum radiator, Boport 1.5 cam, gutted upper, corbeau fixed back seats, and the list goes on.

boosted chicken Offline
Senior Member
An open element breather won't create a vacuum leak.

The only reason the factory routed the crankcase gases back into the turbo inlet was for emissions. The turbo can actually pull oil vapor into it and coat the inside of the intercooler with an oily residue over time which is not good for intercooler efficiency.

If you don't want an open element VC breather, then you will need to put a fitting in the VC (help section in auto parts store) and run a hose to a catch can.
88 TC#1 2.9L tall deck. Essy SVO head, Boport header, BW SX369 turbo, C4 trans, MS2xtra
88 TC#2 drag car project(someday)
88 TC#3 parts car (just needed the header panel...bought the whole car, lol)

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