Supercharged ‘88 GT, closed PCV solution

jjanik191 · Apr 25, 2018

Hi all,

After much research, and blowing oil unnessarily out of places such as the rear main seal, I’ve taken a TON into
consideration and have come to a solution for retaining a closed PCV system. I know this is a topic that has been beaten over the years, but let me know if interested in the details of what I did to solve the issue on my ‘88 GT with Vortech blower and meth injection.

General karthief · Apr 25, 2018

Sure, with pics I hope.

90sickfox · Apr 25, 2018

Who doesn't like more info ? Bring it on.

FoxMustangLvr · Apr 25, 2018

Spill the beans!

jjanik191 · Apr 25, 2018

It is absolutely imperative to run the 4 one-way check valves in the proper direction, so as to not let boost move backwards through the plumbing on either side of the engine, resulting in over-pressuring the crank case. This is where oil finds the path of least resistance, like the rear main seal etc. But not in this system- the check valves let the pressure escape, while the check valves going up the “Ts” simply do not allow for vacuum leaks. The brake booster check valves are 3/8 on either end, and are from late 90s/2000s Nissans and Toyotas. I picked them from a bone yard, but they are available new.

jjanik191 · Apr 25, 2018

You have to remove the guts of the oil seperator from inside the glass bowl (easy one Phillips head screw) and replace with a little bunch of this, just to reduce any slosh and keep the oil in the bowl inside of getting picked up and brought to the upper plenum under normal operation of the PCV system. Also, I keep a vacuum cap on the drain at the bottom just to prevent a possible vacuum, and remove to drain, then replace.

jjanik191 · Apr 25, 2018

Here’s a pic of a typical brake booster check valve off of late 90’s / 2000s Nissans/Toyotas

jjanik191 · Apr 26, 2018

Oil seperator

jjanik191 · Apr 26, 2018

C-F-M baffled one way oil breather

jjanik191 · Apr 26, 2018

Oil seperator disassembled with piece of copper scrubbing pad being installed to reduce slosh etc

Noobz347 · Apr 26, 2018

This is similar to what I have installed on my 86. I don't have enough blow-by to need the breather with check valve but I'm using a third separator between the inlet side of my blower and the driver side valve cover. That line does have a check-valve.

Once I'm able to get back into it, I am seriously considering something more along these lines:
https://rxcatchcans.com/shop?olsPage=t/catch-cans
https://rxcatchcans.com/shop?olsPage=t/catch-can-extras

This is an evolution of what I currently have installed and should look more squared away. I'll probably end up using one of my current catch cans/vials for the blower vent. A vacuum operated check valve will let the oil drain back into the pan when the car is off (still deciding if I want to do this portion or not).

90sickfox · Apr 26, 2018

Seems like the breather that goes to the hose for the plenum will either leak fresh air into the intake ( vacuum leak ).... or leak boost to atmosphere.

jjanik191 · Apr 26, 2018

90 Sickfox, it can’t create a vacuum etc- there is a one-way valve coming off the T prior to the air filter...operating up and out the breather, but closes off for any air trying to make its way in

jjanik191 · Apr 26, 2018

The whole problem this alleviates is too much pressure working it’s way backwards through the PVC system- that is NOT supposed to happen and only creates problems like rear main seal leak, etc

90sickfox · Apr 26, 2018

The hose going to the power pipe doesn't need a check valve. The power pipe before the blower doesnt see boost.

Mine is set up a little different. The hose for the PCV runs from the intake to a check valve, to oil seperator, to pcv valve. The fresh air side runs from intake tube before turbo, to breather ( with open filter ), to valve cover ( dodge sealed breather 5/8 in. )

At idle the vacuum opens the check valve at the intake allowing unburned gasses to enter combustion process. Under boost this valve is closed. The excess vapor is sent out the valve covers to the catch can. If its too much volume it vents to atmosphere, otherwise, it gets sucked into the turbo inlet. The fresh air breather is baffled to reduce oil vapor entering intercooler.

I could stand to improve on this a little. At this time I only have one valve cover vented.

At idle how do you keep fresh air from going in the filter and into the intake ? Or....how do you keep boost from going out of the filter ?

I understand there is a check valve but it only controls one direction of flow. If it keeps pressure from going into the crankcase then it must open ( vent pressure to atmosphere through filter ). That would mean that it vents boost and seals under vacuum....or it opens under vacuum ( idling - letting air in through filter ) and closes under boost. Sealing the boost pressure in the intake.

Do you have a boosted car ???

jjanik191 · Apr 26, 2018

Yes, Vortech V1 SC. It is my understanding that the PCV system is intended to be one direction only- from PCV at rear of 5.0 eventually to underside of upper intake plenum, and that pressure of any kind is NEVER supposed to work it’s way backwards through that system. The factory PCV valve allows that to happen, even others that are supposed to seal it off, which is why I brought brake booster check valves into the equation. So on that side, are you suggesting I remove the breather altogether, but keep a check valve there, to not allow pressure to go back through the PCV system? As it is now, the check valve coming off the T allows pressure up and out, but does not allow for air to enter so as to cause a vacuum.... so you think boost is potentially exiting that breather coming off the upper plenum?

jjanik191 · Apr 26, 2018

I guess the biggest question I have to understand this better then is, doesn’t ANY breather used allow boost to escape theoretically?? If so, then installed at which location DO they, and at which location DON’T they??

Noobz347 · Apr 26, 2018

The breather on the valve cover doesn't "technically" release metered air. That air that ends up as crank case pressure is exhaust air that has slipped past the rings. In other words: That air has already been measured if you're running a mass air system is not a loss. Air allowed to come [in] through that orifice would be by-passing the MAF.

jjanik191 · Apr 26, 2018

Ok thanks Noobz - But what I’m wondering is on the PCV side is if I should get rid of that breather with the check valve at the base of it that lets air out and not in, I’m wondering if that let’s boost out??

Noobz347 · Apr 26, 2018

jjanik191 said:
Ok thanks Noobz - But what I’m wondering is on the PCV side is if I should get rid of that breather with the check valve at the base of it that lets air out and not in, I’m wondering if that let’s boost out??

I honestly don't think it's going to hurt anything unless there's enough velocity coming out to cause it to spit oil mist. If you ever do have excess pressure at the PCV port on the intake, then it is also blow-by and there's no harm in releasing it to atmosphere.

Supercharged ‘88 GT, closed PCV solution

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