crank case ventilation

[lightning bug]

Thanks P.J.

[Richie]

I'll add my 0.2 cents (euro, that is) here to this already lenghty thread.
Running a pipe or hose from the heads to the sump will fill the head on the outside with oil when making a long sweeping turn. This already happens without the hose, through the pushrodtubes! To cover this problem you can lengthen the pushrodtubes on one side, where they'll enter the block. This way you'll create a barrier so the oil can't flow as easily into the pushrodtubes as with standard tubes. Don't block the openings between the lifters and the pushrodtubes completely, duh!
You can use hoses or tubes but then you'll have to fit one-way valves in them, and it would have to be rather large diameter hoses or tubes. At least #10.

I prefer venting the crankcase-fumes into the exhaust as these fumes tend to lower the octane rating when you feed them to the intake (just a little, but it does). This way you could get a problem when running very high compression or boost.
Hope to have added some usefull info.

Cheers

Richard

[verbeekb]

Dank je wel Richard!

The fact that the octane rating would be influenced by the oil fumes never occurred to me.

Brian

[Richie]

You're welcome, graag gedaan!

I believe the Dutchies are coming! As far as I know there are three of us now on this forum!
Nice to know that you're working for a very interesting firm!

Cheers,

Richard

[verbeekb]

Yeah .. .. it -is- a very interesting place Richie, and I can't get enough of it .. They gave me the title "Classic Specialist" *grin* .. and it gives me tons of time to chat with fellow Porsche and VW nuts about all sorts of things, right at work! I also like the looks on the face of a 914 or 356 owner when they discover I don't really care whether they own that car or, for instance, a new Cayenne, or maybe both. And I get to play with Porsche parts every day and get paid for it too! .. Come over some day, maybe with Wally, for some coffee and a little tour, I'd love that.

Brian

[Michael Ghia]

In an oil crankcase breather system, there must be an outlet somewhere into the atmosphere... whether that's straight back into the carb so the gas gets burned or not. If you don't have the outlet (i.e. you use a complete sealed system) it will blow an oil seal as the pressure built up inside above 4,000 rpm is pretty great.
One way which you can help the system is to use a vacuum pump on the crankcase breathing system. If you actually pump air out of the engine crankcase, you'll find you pick up hp. It has been seen to free up 10hp on big V8's.
Racers use this all the time to great effect.
Mike Ghia

[Oliver Knuf]

Porsche engines run close breather systems, as they suck the air again in and burn it. I used to have a similar system earlier on my central air filter unit in my 1st 2l Type 4, but after that, I use the filter mounts left and right. It's pretty identical if you route it into the filter tops or into the atmosphere. The filter tops are a bit better, as you still have a small sucking effect on the breatherbox!

[lightning bug]

Originally posted by Richie

Running a pipe or hose from the heads to the sump will fill the head on the outside with oil when making a long sweeping turn. This already happens without the hose, through the pushrodtubes! To cover this problem you can lengthen the pushrodtubes on one side, where they'll enter the block. This way you'll create a barrier so the oil can't flow as easily into the pushrodtubes as with standard tubes. Don't block the openings between the lifters and the pushrodtubes completely, duh!
You can use hoses or tubes but then you'll have to fit one-way valves in them, and it would have to be rather large diameter hoses or tubes. At least #10.



Cheers

Richard

You can just use windage pushrod tubes for that.

[verbeekb]

How about running a dry-sump pump to assist the breather system? .. And how about lubrication of that side of the pump .. ??

Just some food for thought ..


Brian

[Bugzilla]

Originally posted by BergRace
You need a header with the vacuum pipe in the middle of the collector, along with a one high-flow one-way valve at the conection hose.

Yup. It's called an eductor, and I run one on my baja: http://rap.midco.net/bugzilla/new_wheels/wheels022.htm
http://rap.midco.net/bugcollector/DSCF033.jpg
http://rap.midco.net/bugcollector/apr03001.jpg

It is very simple to build one... just weld a piece of pipe to the exhaust, near the collector. Get a one-way valve (I think it is a GM part) and thread it on the pipe. Then run a hose from the valve to the breather tower, or any place on the case you want to vent. I tapped the valve covers and connected them to an aftermarket breather with an oiled foam element. This provides a place for clean fresh air to enter the crankcase. The eductor pulls quite a bit of vacuum, and you don't contaminate your intake charge... it all goes out the exhaust. The one-way valve keeps any pressure pulses (like a backfire!) from traveling to the crankcase.

If you want more details on how I built mine, let me know.

Troy

[Chris Percival]

Very neat! Do you believe that is the optimal angle of the pipe? How is the pipe finished inside? Its is square, or it cut parallel with the exhaust pipe?

[Bugzilla]

Originally posted by Chris Percival
Very neat! Do you believe that is the optimal angle of the pipe? How is the pipe finished inside? Its is square, or it cut parallel with the exhaust pipe?

The pipe was just an off the shelf piece from a plumbing store, matched to the threads on the valve. The research I did said 90 degrees to the exhaust flow is optimal, but I put mine at 45 degrees for a clean install. I had the whole thing welded up and sent out for ceramic coating. The guy who welded it for me said he did the weld first, and then ran a drill bit down the pipe to open it up to the exhaust flow (rather than drilling the hole first, then trying to weld to it.

Here is an interesting thread describing the concept: http://www.eurospares.com/sucker.htm

And some pics of another install: http://community-2.webtv.net/PAGEBUI...ASEEVACUATION/

You can even buy a kit, if ya want: http://www.csaponline.com/sale/moroso/moroso.htm

Troy

[Chris Percival]

And the valve doesn't get too hot? What are these valves most commonly used for? (so that I can go into a parts store and ask for one)

[kdanie]

The kits I have seen in the speed shop catalogs are designed for an angled installation like shown in the pictures.
ken

[Bugzilla]

Originally posted by Chris Percival
And the valve doesn't get too hot? What are these valves most commonly used for? (so that I can go into a parts store and ask for one)

The valve is a check valve used for the GM A.I.R system (I think). It is a "Standard Motor Products" part # AV7. Pick an application from the following page that uses the AV7, write down the GM part number, and take it to your favorite parts store. http://www.smpcorp.com/catalog/web_c...0CHECK%20VALVE
It should cost less than $15.

I've used mine for about 6 years on the baja. That's a 1600 DP with a tri-mill exhaust, BTW. And it was already starting to rust before I sent it out for ceramic coating (yeah, I sandblasted it first)... the rust you see is under the coating. Next time I will use a NEW exaust system.

Troy