How little crankcase venting can you get away with?

[RT]

Here's my setup; 1600DP, forged Mahle P&C kit, stock heads, TS 2nd rings, single 40IDF, 8.5:1 CR, machine-in sand-seal, balanced, Webcam 86 grind. The factory oil fill is a type with only the top breather pipe (no draft tube) but its much bigger than the one with the road draft tube so in theory it should flow almost 2X much. It's just about together.

I wonder if I can get away with just the one large vent outlet with a K&N filter (bigger than the common one). Some (like Berg) suggest you need a clean air "intake" but unless you got intake vacuum sucking on the other end, I would think internal pressure would be pushing any out additional openings. Since this is a buggy motor, I want minimal hoses hanging "out there".

[turboblue]

RT

Since you are a 1600. you might get away with just venting the oil filler with the K&N style filter. Better choice would be doing the valve covers too. The reason you need to use the filter is the crankcase vent system pulses air and fumes in and out. The filter will keep crud and dust from being ingested into your vent system.

[Class 11 streeter]

Do you have a counterweighted crank?
If you do not, go ahead with your plan.
If you do have a C/W crank and your engine spouts oil leaks, consider running valve cover breathers.

Not my rule, an engine builder I trust swears by this.

[vicsvw]

Pull out the oil dip stick and rev up the motor, if the oil is pushed up to the top of the tube or out of the dip stick tube then you need more venting. Vic www.vwhelp.com

[RT]

Thanks guys. I'll try the dipstick test. Its not a CW crank but I did have the entire engine balanced. I can see how the counterweights would create a lot more turbulance in there.

[Leatherneck]

Pull out the oil dip stick and rev up the motor, if the oil is pushed up to the top of the tube or out of the dip stick tube then you need more venting. Vic http://www.vwhelp.com

It was a sad day when Vic closed up shop, health problems forced that. What a wealth of knowledge and a cool buggy shop he had. At one time I was thinking about buying his business, still wonder what would of become of that.

Anyway I have my cylinders leading up to a catch that, you can catch of a glimpse of it at 48 sec, I put a piece of fuel cell foam in it. The reason I did that was I get some overflow from it spilling on whatever is below it. Hoping the foam will keep the oil from being able to blow out of it.. I have a K&N style filter that goes on that chrome piece. Not sure how or why it is

https://www.youtube.com/watch?v=FACMqyK ... e=youtu.be

[Marc]

....I can see how the counterweights would create a lot more turbulance in there.

What they do is create a "labyrinth seal" making it difficult for crankcase vapors to commute back and forth through the windows in the center main web as the volume of each end of the crankcase changes by half the displacement twice per revolution - that forces more to travel up & down the pushrod tubes, interfering with oil drainback from the heads and exposing the valvecover gaskets to greater pressure pulsations.

[Ol'fogasaurus]

With the VW engine being a pancake/opposed engine oil drain back isn't the greatest in the first place. Off-road we usually get rid of the stock vent pipe as it, like most of the old engines that used vent pipes, wants to plug up pretty easily. We usually use a breather box hooked to the valve covers then the drain back is hooked to the oil fill on the generator/alternator stand. Ma Gravity can then work the oil back into the engine once it cools off and goes back from a vapor to a solid also aiding in venting the air pushed around by the pistons going up and down ( I mean sideways and pushing against each other ).

On the sand we often travel at angles that most vehicles don't spend much, if any, time (like up and down the face of the dunes especially when side-hilling which is traveling across the face of the dune) at so venting and a deep sump is a bit more important than putting down the Autobahn with the engine revving at just above idle .

[FJCamper]

Extra Case Vent Experiment

Porsche vented the 4-cam Type 547 above the 1-2 cylinder side. Marc's advice about stroker cranks hampering case ventilation is very accurate.

We experimented with improved case breathing by installing a threaded AN-style fitting above the 1-2 side, and it worked so well we wished we'd made it larger. We ran the line into the base of a vented, filtered, catch can. oil could then run back down the tube to the case at low pressure.

When Porsche started using counterweighted cranks on the 356 SC and 912 engines, the factory added vent tubes to the top of the engine heads rather than to the valve covers, so as to allow the valve covers to be removed without complication.

[Marc]

Some OEM DP1600 VW heads have steel vent tubes pressed in (and you'll also find the undrilled boss in the casting of some replacement heads).

I believe it was part of the California emissions package for Type IIIs in `73 (perhaps `72 also). They take a ~½" hose (12mm?)

[Ol'fogasaurus]

Pile, that is an interesting fix to say the least!

Why that location or was it just a convient spot. Not against it, just curious as to the choice of spot.

Correction:

Leather corrected me that the question should have been directed to FJ not Pile. Sorry Pile!

I was curious what drove the location choice as the decision might help someone else if they want to use FJ's trick.

Lee

[FJCamper]

The 1-2 cylinder side of the case has no oil galleries, and a doghouse cooler gets in the way of a top vent on the 3-4 side.

From inside the case, you have roof reinforcing ribs that limit your working room, dictating the size and location of the vent. My advice to anyone doing this is to go at least 12AN.

FJC

[Ol'fogasaurus]

The 1-2 cylinder side of the case has no oil galleries, and a doghouse cooler gets in the way of a top vent on the 3-4 side.

From inside the case, you have roof reinforcing ribs that limit your working room, dictating the size and location of the vent. My advice to anyone doing this is to go at least 12AN.

FJC

Thank you sir. To the point and concise.