1915 breather options

If it's leaking oil from the oil filler cap or from behind the crankshaft pulley after a freeway run of 70-ish mph for a while, or;

 

If you have it idling and remove the oil filler cap and it belches a lot of oily air; 

 

Then you're probably not providing enough venting.

 

You should be OK with the dual valve cover vents to a 912 oil filler tower (which, in itself, is a breather box of sorts), but try running one or two 1/2" ID hoses from the top of the filler tower to the carb air cleaners.  I route mine to the top, middle of the cleaner cover, getting inside of the filters.  

 

 

But that's my opinion and I'm known to be Grumpy    

This is the actual filler:

 

It is blowing a bit past the oil filler cap or from behind the crankshaft pulley after a freeway run of 70-ish mph for a while. No belching of oil filled air out of the cap at idle. There is air coming out but it doesn't appear to be oil soaked.

 

So before buying a breather box, it's your suggestion to take the existing vented line and T it off to the right air filter base? Alternately, I could 'T' each hose off to each air filter base?

 

No need to run off and buy this?:

I've ordered a new sand seal, this time I got the one with the 'double lip'.

 

Thanks for the info!

Ted

I don't think you can have too much venting. I installed a super-sized breather box I got from Henry at Intermeccanica. I run a line from both valve covers, a line from the filler tube to the right carburetor top (and tee'd to the breather box) and one from where the fuel pump used to be. That curtailed almost all the blowby through the pulley. I still get a tiny bit during long, hot spirited drives. No, I don't have a sand seal.

Any vw engine larger than a 1600 needs additional breathing. both valve covers should breathe to a separate breather box.(I use the RLR 1.5qt design on most applications) . you should use at least a AN8 or better yet AN10 to the breather box, these breather lines should not have any dips or low spots. When you have a bend or low spot the lines can fill with oil and the breather hose becomes useless. From the breather box you run a hose to the fuel pump block off plate. If you have a stock fuel pump then run the hose to the oil filler housing.. 

 

So we are all in agreement, my motor isn't breathing as well as it could/should.

Roger that. I'll look into getting a proper breather setup.

THANKS!

Hate to say it but high leak down (bad rings) could cause this even if it's vented properly. If your engine is fairly fresh or not using a lot of oil you are not having a ring problem. I once saw a 65 GTO that was blowing by so bad the dipstick would push out.

Agreed, you should do a compression check first so you aren't chasing your tail with crankcase venting (you should run the external vent line to the carb, it'll lower the pressure better than just being below the car). Especially with your comment that it is doing this "again" which would seem to imply it was doing it before, you fixed it somehow, but the situation has worsened where it needs to be fixed again.

 

The other possibility is there is some damage to the pulley surface where it rides on the seal which is making them fail.

Don't give Ted a heart attack.  This is a new motor. The very least he should have a better breathing system. He will need it for motor in the future. The compression and leak down test would be good to know anyhow since the original owner of the engine wasn't true to the motors condition

Ted;

 

Does the oil filler tower mount easily to the alternator stand? Have you seen these anywhere in black vs. chrome? And not to second guess either you or Gordon, it sounds like Gordon pipes his to the top, center of the air filter container, not the base. Or is that what you meant.

 

Art

Art's correct - I have a CB Performance breather box which takes the place of the 912-style filler/breather.  I do not vent the valve covers and have two 5/8" ID hoses running from the back, top of the breather box, one to each air cleaner where they are attached at the middle of the top of the air cleaner cover, not the base, so they vent right into the carb throat.

 

I started with 3/8" ID hoses to the air cleaners but had quite a bit of seepage behind the crank pulley, so I migrated to the 5/8" size and that has mostly stopped any pressurized oil seepage, except for freeway driving at 80-ish for a longer period (couple of hours) where I get a very small seep at the crank pulley.   Not enough for me to worry about (I am not a fanatic about VW engine leaks - I simply accept them as the normal course of events).

 

In ten years I have never seen any indication of oil coating in the carb throats, so the CB breather seems to be separating the oil from the crankcase air quite well.

 

 

A "TOTAL SEAL" RING SET ON THE MIDDLE GROOVE OF YOUR PISTONS REALLY SOLVES THERE PROBLEMS ON 1700 CC AND UP ENGINES GIVEN IT'S A LOT TO PULL THE ENGINE APART TO PUT THEM IN. BUT...A LOT LESS HOSES TO DEAL WITH....BRUCE

Just ADD TO THE CONFUSION: i HAVE a 2332, and it has single hose from the oil filler pipe to the pass side carb.  I suppose there is a little negative pressure there.  No vents from the valve covers.  No gush of oily air from the filler when cap is off and engine running.  Many here think I am nucking futs, but it is what it is.  Seems to be fine, no oil out any seals, nary a drop on the garage floor.  What else can I say?  Breather boxes hooking up valve covers to a seperator box that can drain back to the crankcase and a vent to the carbs is a fine system.  Is it necessary?  Perhaps.  If he engine passes gas around the rings and/or valve guides, then venting is going to be needed.  Every engine no matter how well made will pass at least SOME gas by the rings.  If all fits like it should, this will be minimal, and easily handled.

 

$0.02 worth -- nothing more, and maybe not even worth that.

 

El Frazoo out.

Hey Art,

That's the one I have on my car. I scuffed it with some 300 grit and then cleaned it up with some 600 before priming it and painting it black with high temp paint.  It was on my 1600 and  now my 1915. No problems so far with the paint.

 

I will look into venting the heads directly into the carbs. I guess I'll also do a compression test + leakdown.

 

I'm not really worried if the motor is producing a bunch of blow by. If it is, it is. I'll fix that too.   I went into it knowing it would be an $1100.00 learning experience. It runs great. No problems at all. I just hate oil leaks.

 

I'm learning as I go. Not a real big deal.

 

I guess I'll shelf the question about the oil temps gauge. I'm afraid of what I'll learn.

 

Thanks for the replies!

Ted

Ted- As already mentioned, larger diameter hose will give the system more volume and slow down the air movement so some of the oil will fall out of suspension before it ever hits the breather; I think Gordon's gone the right way with 5/8" hose. I've read on STF or the Samba where guys are having success with only venting one valve cover; the left side fills up with so much oil from the spinning of the crankshaft (I think we've all seen the video of the valve cover full of oil at higher rpm's) that in extreme situations it will fill a breather box. Also, a small baffle in front of the opening in the valve cover helps prevent oil being sucked up the tube to the breather. I think joining the 2 valve cover lines (twice as much air movement in the same size tubing; the idea is to slow down the air movement as much as possible) isn't helping. 

 

Are there baffles in the unit you have? You should be able to look through the filler hole and not see the bottom. I've heard of guys putting a piece of copper or stainless "Chore Girl" scrubber in the breather to add more surface area for the oil to condense on. I don't think venting the valve covers directly to the carbs without going to a breather box first (where the oil can drop out of suspension) is a good idea.

 

Hope this helps. Al

I'm curious;

 

When did the vented valve cover thing start?

 

When I was a kid and hanging out at a Porsche engine builder's shop, I don't ever remember seeing vented valve covers on a 356 engine, nor have I seen any recently when visiting local shops catering to the 356 crowd.

 

All the engines I remember had the 912-style oil filler/vent with a single hose going to one carb, just like Kelly has (or the early ones just ran the vent tube out the bottom to the ground). 

I think the Porsche 356 actually vented the heads, not the cover.

Thanks for all replies. I'll get this thing skinned. I may end up upgrading the P/C and rings if it fails a leakdow.

Not a big deal,
Ted

Gordon- Venting through the valve covers (and the tiny little breather boxes that aren't nearly large enough) has been done by the VW performance crowd since I've been involved (1974?). 

Makes it a lot easier to remove the covers for servicing that way.

 

 

 

One of the biggest problems for good PCV in my opinion is the lack of good vacuum source on modified engines. You can't run the PCV to the intake manifold on a carbed engine because being below the carb, the air it sucks in is unmetered and acts like a large intake leak.

 

Running it to the air cleaner is the right way to do it except that the standard air filters for aftermarket carbs are not fully enclosed in a shell with a snorkel like on a stock car. Because the filter element must be sized large enough to not present a restriction to the airflow, that excess airflow capacity makes it tough to generate a low enough pressure inside an exposed element air filter to make the PCV work well.

 

If you look at a stock vehicle, the air cleaner box has a snorkel opening that is about the same size as the carb throat. Because the snorkel and carb are sized the same, the airflow is the same at each end which means the pressure is the same everywhere inside the air cleaner box. Makes it easy for the PCV to get the vacuum needed to work correctly.

 

So what you really should have is the valve covers vented to a breather box (the valve cover vents are the air intake), a small diameter drain tube from the breather box to the oil fill tower (it's just a drain, not a vent), a larger diameter hose from the crankcase / oil fill tower connected to a PCV valve (this is the air outlet), the PCV valve then connects to a proper air filter box with snorkel. By making the drain hose smaller than the PCV hose you bias the airflow direction so it pulls air in through the valve covers instead of directly from the breather box drain.

 

One of the other things that really should be done is to add a windage tray to help with the 3/4 side oil drain. But that requires splitting the case.

 

PCV routing changes a bit with a turbo engine as you have to account for the positive intake pressures.

 

As an example from a turbo Subaru engine:

There is a balance tube that connects the left valve cover, right valve cover, and crankcase together to help equalize pressure inside the engine. There is a second vent port on each valve cover that are T'd together and then they connect to the intake after the MAF but before the turbo. There is a second crankcase vent that runs into a T connector, one end going to a PCV valve in the intake manifold below the throttle and the other connecting to the intake after the MAF but before the turbo. Off boost, air is pulled into the valve covers and into the manifold through the PCV valve. On boost, the PCV valve is closed from the pressure, but because the pre-turbo intake is under vacuum, air gets pulled in through the valve covers, through the case, and sucked back out via the intake again. Since the intake hoses are connected after the MAF, any air entering the engine via the PCV system has already been measured and thus AFRs remain stable.

Justin, thanks for sharing those great tech tips! I enjoy learning the logic you present with each explanation.  

I have an rpm-triggered solenoid hooked up to an exhaust evac. Plus a custom breather tube. Works great.

Good point. I should have stated venting the heads to a breather box, then from the breather any oil can drain into the tower (which has baffles) and then I can vent from the tower to the carbs.

 

Thanks again!

Ted