My Breather Restricter Mod

[drddan]

I had oil blowing out of the valve cover inlet tube, through my fancy new breather filter, onto my valve cover. (my newly painted valve cover, I might add!) I was able to fix it with the help of iceracerdude and bravekozak
Iceracerdude suggested I do a write-up, as there are members here with the same breather/carb set up as mine. If anyone experiences this problem, this is how I fixed it.
This is the inlet tube breather filter, that oil was coming out of

It seems that the 3/8 inch I.D. of the inlet tube was overriding the 3/16 I.D. of the PCV valve, loosing vacuum pressure needed to draw air in through the inlet tube to the PCV. So by restricting the inlet tube I.D. to 3/16 I.D. same as the PCV, it would have enough vacuum to draw the air through the inlet to the PCV. This is how the stock inlet works, as the stock rubber tube on the inlet tube has a restriction built into it, about 3/16 inch I.D.

I made a nylon restricter plug to fit into the inlet tube. I made this from a plug that comes in new master cylinders to plug the brake line connections.
One was about the right size and had a 3/16 hole almost all the way through it allready!
I drilled it the rest of the way through, stuck a 1 1/2 inch long 10-24 bolt through the hole, screwed on a nut, and chucked the bolt in the drill press.
I then turned on the drill press and with a file took it down to the 3/8 diameter to fit the ID of the inlet tube, and the head to just below 1/2 inch diameter.
A Restricter was born!
I then pushed the restricter plug into the inlet tube of the valve cover, reducing the ID of the inlet tube to 3/16 inch and re-installed the breather filter. So now the 3/16 dia of the inlet is equal to the 3/16 dia of the pcv valve. It now has the nessesary vacuum to pull air into the inlet and through to the pcv. No More Oil On The Valve Cover!
It is all pretty and red now.

Here is the restricter

[iceracerdude]

Great write-up, a lot of guys have been curious about the cause and affects of modifing their stock breather configurations. The beauty of your design is that it's universaly functional for all of the na designs, as well as being a clean, inexpensive and ultimately uncluttered solution!
Thanks for sharing.

[devon527]

Awsome write up, I am trying to figure out how to change up my air box on my 88, and need to figure out what and how to change things up to make it still work. This helped alot

[boydg1]

.... What do you do for BLOW-BY when the pressure is so great it goes the other way, out the breather tube? Thanks

[drddan]

.... What do you do for BLOW-BY when the pressure is so great it goes the other way, out the breather tube? Thanks

Well the "adaptor" I made was to help with the blow-by, and it does as long as I clean my PCV valve about once a week. If I forget to clean the PCV then I get to clean my valve cover instead! :p

[blkfordsedan]

.... What do you do for BLOW-BY when the pressure is so great it goes the other way, out the breather tube? Thanks

If the pressure is so much that it's blowing excessive oil out that breather tube, you can install a catch can in the line. It kinda ruins the whole "clean & simple" principle, but is very effective. You can get them on Ebay for around $20.

[boydg1]

.... Not so much oil as it is SMOKE. thanks.
.

If the pressure is so much that it's blowing excessive oil out that breather tube, you can install a catch can in the line. It kinda ruins the whole "clean & simple" principle, but is very effective. You can get them on Ebay for around $20.

[blkfordsedan]

.... Not so much oil as it is SMOKE. thanks.
.

LOL, mine looks like a steam locomotive. You could run the other hose on the catch can back into the intake tube where the original hose went. That will keep it from blowing oil into the intake tube & VAF meter and should suck the smoke/steam back in the engine. Once the blow-by get bad (like mine), there's not much you can do.

[Oren09]

I was wondering why my intake tube was full of oil. It drips when I remove it. I guess it coming through the breather tube (FI car). I have a lot of blowby at idle. I can feel, see, and hear it with the oil cap off.

[blkfordsedan]

LOL, that would be why. I could only drive about 100 miles at highway speed before it would collect so much oil in the intake tube that when I would go up a hill, the oil would run back into the throttle body and the engine would mis-fire & smoke out the exhaust. I would have to dis-assemble the whole intake assembly and drain the oil every other day. Once I installed the catch can it would collect 95% of the oil. Only problem was it only holds about 3/4 of a quart and I would have to drain it every day. When I swap my B6 I plan on keeping the catch can (maybe move it to the PCV hose).

[Oren09]

Is there some way I can plug the intake tube connector and open up that valve cover vent to the atmosphere? I could use the tiny filter like on the carbed car pictured above, but with how much oil is in the intake, that would kill the filter.

[iceracerdude]

Just one of the designs in this "vent upgrade" you're supposed to be seeing here, is the differences in the hole sizes between the vent and the pvc tube. Because of those differences, an important vacuum differential is achieved, thus scavenging most if not all of those gasses or smoke. When the use of a "catch can" is employed, it's function is that of an "oil seperator". At idle, or on very heavy compression braking the car is "basicaly" creating the most vacuum it ever will, when the vent tube hole is smaller (like an 1/8 inch) than the pcv tube (or the suction end of the circuit) AND the pcv valve is "good", it will pull those vapors directly into the intake plenum and you won't get that smoking out of the vent hole or oil in the intake tube and or throttle body.
Just one of the reasons Drddan did this was for the uncluttered look!

Here's a picture of my setup, but without the use of a filter, just a tube pointing upward. If you magnify, and then look real closely at the hole in the end of the tube,
you can see a slight bit of oil dampness:


I run 10 pounds of boost pressure against my pistons, so my chances of "blow-by" are pretty good wouldn't you say, but if you take a close look at the picture, you'll see I don't have any oil on my valve cover. This is because I acknowledge and respect the engineers design of maintaining "a pressure (or vacuum if you prefer) differential". That, and I'm not trying to save $4 on pcv valves.

[Oren09]

Ok. Thanks iceracer. It makes sense now.
My PCV is new so I need to work on the tube.