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Tue Apr 13, 2021 4:58 pm

A friend of mine will be connecting the following filters directly to his valve covers:
https://www.spectreperformance.com/cat/air-filters-breather

He asked me if it would provide proper ventilation to his newly built 1904cc engine. I told him I would check with the experts here on Samba.

Thanks

Tue Apr 13, 2021 5:32 pm

they'll vent and they'll also get saturated in oil then collect dirt & dust.

Tue Apr 13, 2021 5:40 pm

Not good to install those directly to the valve covers as stated above.

Install a breather box on the firewall and run hoses to it

Tue Apr 13, 2021 5:55 pm

DerrickfromNC1 wrote: A friend of mine will be connecting the following filters directly to his valve covers:
https://www.spectreperformance.com/cat/air-filters-breather

He asked me if it would provide proper ventilation to his newly built 1904cc engine. I told him I would check with the experts here on Samba.

Thanks

Let him do it then post pics after he drives it for a while.

Tue Apr 13, 2021 5:59 pm

A breather box separates the oil mist from the air. The oil drains back into the engine and the air vents to the atmosphere.

Wed Apr 14, 2021 10:13 am

Just vent the 1/2 side

Wed Apr 14, 2021 10:18 am

Breather on crank case only. A 1904 doesn't need valve cover venting.

Wed Apr 14, 2021 3:23 pm

Two guys with quite a bit of engine experience had different opinions as to were to sent the crankcase gases, in an recent post.

Rich Hunt is my carb rebuilder and Alstrup engine specialist

Frist of all I agree you do not need get the gases from the valve covers unless you have a much larger engine.

The discussion was were to send the crankcase gases to the carbs or atmosphere

Rich Said Atmosphere, knowing from his experience it may create issues in the carb like the oil collecting dirt and causing problems.

Alstrup said to the carb or carbs.

Well in my photos I went to Atmosphere and my bug started smelling of burned oil.

Then went to the Carb and the smell went away.

If it did not smell I for sure would have went to Atmosphere.

Sorry Rich, smell won over your logic.

To show how little a breather you need, check out mine made from a aftermarket oil filler tube turned upside down.

Oil and gas go in and up, gas has no problem going to the carb, oil gets slowed down in my inner tube with the holes and drops down the tube (see slots cut at the bottom of that tube) and falls back into the crankcase.

My aftermarket upside down oil filler tube works great.

Wed Apr 14, 2021 3:41 pm

kangaboy wrote: Breather on crank case only. A 1904 doesn't need valve cover venting.

There is not enough information about the engine to make this determination. You have big cam with heads to support it turning high RPM; you will need to vent more than just the case.

Wed Apr 14, 2021 5:18 pm

k-weaver wrote: kangaboy wrote: Breather on crank case only. A 1904 doesn't need valve cover venting.

There is not enough information about the engine to make this determination. You have big cam with heads to support it turning high RPM; you will need to vent more than just the case.

yup. then add a turbo and see how much venting you need, especially if the engine is older and has any blow by.

Wed Apr 14, 2021 8:22 pm

Here is a very informative read on the subject.

https://shoptalkforums.com/viewtopic.php?t=118958

Thu Apr 15, 2021 4:43 am

Nextgen, how high do you rev that Type IV?

Thu Apr 15, 2021 6:02 am

A few things that Shoptalk forum article has wrong:

Porsche 912 motors only vented the 1/2 side. The 3/4 remained sealed.

It's not the oil ring that "flutters" with high crank case pressures. It's the top compression ring.
Has more to do with ring gaps, but excessive crank case pressure contributes.

ONe of the big points that is missed for dealing with case pressure is ring gaps.
Most folks don't think about it too much. But gaps make a big difference in the amount of blow-by at high rpms (when you are worried about it).

Another one is "internal case porting". This is blending and smoothing the breather ports in the #2 main bearing web. The ports are usually full of sharp corners and very restrictive. Blending and smoothing will allow the case to breather easier and will reduce the amount oil spray in the gasses that vent.

Thu Apr 15, 2021 10:53 am

richardcraineum wrote: k-weaver wrote: kangaboy wrote: Breather on crank case only. A 1904 doesn't need valve cover venting.

There is not enough information about the engine to make this determination. You have big cam with heads to support it turning high RPM; you will need to vent more than just the case.

yup. then add a turbo and see how much venting you need, especially if the engine is older and has any blow by.

I guess I'm just lucky then. Actually hit 24psi at the track last weekend.

Thu Apr 15, 2021 11:23 am

Jason37 wrote: Here is a very informative read on the subject.

https://shoptalkforums.com/viewtopic.php?t=118958

Just for the record....that conversation is missing a lot of info for type 4.

And....it is only speaking of case venting with a carb system.

The factory type 4 system for fuel injected 411/412 and 914 (and to some extent the L-jet injected bus)....is actually a "pull through" system.

It pulls filtered air from the air cleaner (it has a special outlet on the AC).
Then...it pulls this air through a flame trap/splitter....
Then...through 12mm hose into each rocker box where It helps to pull excessive oil and any gases....through the pushrod tubes into the case
Then......gases from the case pass through the "Z" baffle cast into the type 4 case losing some oil vapor....
Then the gases pass through the oil chimney baffle (which works very well by itself for oil separation)....and this is where the "chore boy" scouring pads would be installed........

Then through the factory PCV valve.....and into the intake manifold through the 12mm hose.

So.....type 4 factory injection used manifold vacuum to pull fresh air from teh AC...through the rocker boxes....through the case....out the top and through the manifold.
Most effective PCV and oil separation system I have seen in an air cooled VW.

It takes more vacuum than most carbs generate.

The whole point I was getting at is that in type 4....the vent tubes on the rocker boxes from the factory....were NEVER designed to vent OUTWARD. Why would you want to pull all of that crap through your valve gear?

Ray

Thu Apr 15, 2021 11:39 am

Madmike, do you think I rev it high if it lasted 30 years, ha.

Seriously like anyone with a T-1 or T-4 Normal revving unless I am showing off on a highway.

It was not built for racing, the engine came out of 914 with a top speed of 127 mph.. I have done 100 easy, 60 to 100 is seconds BUT I will never do it again.

With all the stuff I did to make it hold the road, after 90 the steering gets light.

Freaked me out, but what freaks out cars like BMW's is when they tailgate an hit the gas. W T F!!!

It is a 2.0 71 mm stroke 66 mm. a bit more torque.

Highway speeds it what I wanted and what I got.

Thu Apr 15, 2021 12:02 pm

MadMike LIke I said I don't baby it, this is last years 60 mile cruise in upstate NY and to the top of Bear Mountain. 50 bugs ( some did not make it )we were 70 mile from NYC and you can see the skyscrapers.

The River is the Hudson, just below West Point Military academy.

https://www.youtube.com/watch?v=Ap0NeT2Q2vc

https://www.youtube.com/watch?v=xSfdw4eAyLI

https://www.youtube.com/watch?v=lIkhkOpF7kU

Thu Apr 15, 2021 12:02 pm

MadMike LIke I said I don't baby it, this is last years 60 mile cruise in upstate NY and to the top of Bear Mountain. 50 bugs ( some did not make it )we were 70 mile from NYC and you can see the skyscrapers.

The River is the Hudson, just below West Point Military academy.

https://www.youtube.com/watch?v=Ap0NeT2Q2vc

https://www.youtube.com/watch?v=xSfdw4eAyLI

https://www.youtube.com/watch?v=lIkhkOpF7kU

Thu Apr 15, 2021 1:31 pm

Just wanted to know what rpm's you shift at? ,is all :wink:

Thu Apr 15, 2021 3:18 pm

Oh !!!!!!!! My eyes are the tools I use, it is my ears.

Not a big Tach, Hmmm, now looking at it, I should have put it were my Volt gauge is located.