What is the cheapest and best PCV check valve for boost applications?

Fresh filtered air would go in the normal way, from just inside the air filter on the clean air side. No change there.

I want to keep my vacuum PCV system functioning, and so it looks like I need two check valves. My plan is to installed a one-way valve from my normal PVC valve flowing toward my throttle body PCV connection so boost does not back feed the PCV valve but the throttle body can draw gasses out of the engine.

Then, between the old regular PCV valve and that new check valve, I want to install a venting check valve that runs out to air. This way if the crankcase pressurizes or the line back to the old PCV valve pressurizes, the pressure can vent out to air......but that open line cannot suck in and cannot vent boost. That line will be an exit only in the event something pressurizes beyond what the clean air inlet can handle.

I'm looking for a one way low pressure check valve of maybe 3/8 inch hose size, or whatever the 5.0 Ford PCV valve system uses.

 

on GM stuff there is a check ball in the pvc valve, maybe the ford is different??

 

What car?

You can run part of the vent system pre turbo to create a draw at high RPM and still use filtered air to be pulled back into the engine through the crank case. I would just buy a one way valve on Jegs or something with barb fittings that can go inline to a stock PCV valve. Honestly, since I went to a catch can system, I won't ever try to use a stock PCV system, most of the time they don't have enough flow for blowby created by most turbo systems or increased cubic inch engines. I tapped the back of both of my valve covers to run to a catch can, then had a line running from my filler neck to pre throttle body. It's worked well at keeping crank case pressure down.

 

This is the Dart 363 cu in patterned after the Ford 302 block. Everything is brand new parts. It's in a 1989 Mustang 5.0 LX mostly street car. About 15 pounds boost.

I have a Ford Turbo Coupe PCV valve, which has a very good reverse pressure hold off.

I want to draw nice clean filtered air in the valve cover (which I can take care of with a small breather filter) and draw it out the PCV valve (which is at the intake manifold rear, with a manifold oil shield in the lifter valley) to the throttle body's normal PCV input. When under boost, I want to vent the crankcase out to atmosphere from both the valve cover and the the lifter valley PCV valve.

This means I need two check valves. One to prevent the boost from pressuring back down the line to the PCV valve that vents out, and one on that line's atmosphere vent outlet to block air from coming in when under vacuum.

Under vacuum, it draws clean air in through the normal path to the throttle body keep my oil and crankcase clean. The rearward air vent is blocked by an exit only check valve to atmosphere. Nothing can come in there.

Under boost, a check valve prevents the throttle body from backfeeding the vent system. Both the rear and front vents can vent directly to atmosphere.

The normal PCV valve is a moot issue with this system, but as long as I have it I'll keep it for double protection from pressurizing the crankcase.

Anyway, I need two check valves that work at low pressure. One to block the vent off from sucking air, and the other to prevent backfeeding the vent from the throttle body. So who makes a high flow check valve that will fit 3/8" or slightly larger line?

Thanks, Tom

 

I would just let the turbo coupe pcv valve do it's thing on idle and over 0 in hg. Then tap both valve covers for venting during boost. Have you tried jegs or 363summitracing? Like I said, you should route lines from the valve covers pre turbo, you get a draw through effect during accel and dont get oil mist gathering in your engine bay. Just slap a catchcan in between. You WILL need more than one vent for a boosted 363. Otherwise you are going to start pushing oil past your seals and gaskets. Ask me how I know..

 

Oh, forgot to add. The turbo coupe pcv valve SHOULD stop boost from coming into the crankcase, specially at 15psi, which is what the turbo coupe ran from the factory.

 

But that is exactly why I want a pair of check valves.

I need two check valves to automatically steer the engine pressure out so I can route the pressure out under boost, but have it draw through normally when under vacuum. Surely someone uses a check valve?

 

Tom,

I needed some check valves to keep boost from screwing up my power brakes and found this company. I'm sure they would work fine for what you are trying to do, and they can be purchased individually. Stuff I ordered showed up real quick and worked great.

http://www.usplastic.com/catalog/item.aspx?itemid=23369&catid=489

David

 

You can also go to any parts store and use the power brake vac check valve. They are very tough and easy to come by. They also come in 90* and inline.

 

Thanks David, I think those would work if the local auto store parts route does not pan out for me.

Good suggestion. I'll ask the next time I'm at the store. So far so good during break in. With the lines open I'm not pumping oil out of the rear PCV valve or the valve cover oil filler tube's hose connection. The Ford covers only have a connection on the passenger side valve cover for the year parts I have. But I still want to do the vacuum system clean air draw through to keep the nasty gasses away from the oil while cruising.

Tom

 

I guess we have been doing something wrong all these years. On our TT340 Challenger we have just used a plain old Mopar PCV valve feeding right into the intake manifold plenum area. It shuts off under boost so no boost to crankcase. The filtered inlet to the crankcase is a K&N filtered breather cap on the opposite valve cover. It flows both ways, so at high loads when the crankcase goes positive it released the pressure to the air. The K&N traps any oil vapor very well, and on our 340 only needs cleaning once a year. We have run this setup for 25 years with out issue.