Quick one: breather hoses to oil tank (2.7 & SC era)

[cowtown]

Can someone set me straight on where on the oil tank the main crankcase breather hose mounts? Is it on the oil filler neck, or on the upper tank fitting? Car is a '75 911S

And what's the other one? I know, I should have taken a few more pictures during the engine pull.

Thanks!

[k9handler]

mine was mounted on the filler neck...but that engine is gone now!

[cowtown]

Thanks K9. Where's the other tank breather connection go?

[Jim Sims]

Upper fitting (one closest to oil cap) attaches to passenger side of airbox using the hose with the a spiral twist in it. The lower fitting on the oil tank attaches to the engine breather (top of engine breather) hose. Jim

[cowtown]

Thanks guys.
Colin

[jwetering]

Sorry to beat a dead horse, but K9 and JimSims contradicted each other and I'd like to clarify. I'm trying to figure this same plumbing out because after my conversion to webers, the lower tank vent spews oil all over my engine compartment, while the upper vent (in the filler neck) is attached to the engine case breather. I was thinking to attach the engine case breather hose to the lower vent and put the little K&N filter on the filler neck breather. Am I "allowed" to do that ?

[k9handler]

Jim is correct, just wording on my part was bad.

[silverc4s]

Jasper,
Your solution will work, unless you have smog testing there - and then only if the inspector knows / notices the open air breather...Good Luck;-)

[Mukilteo911]

A friend of mine put filter on the end of his case breather tube and closed off the hole on the oil filler tube. does this affect the vacuum of the engine ? Any other issues to consider. I get a lot of foamy junk in my oil filler tube. Yuk. I only get 40 minutes each way in the car and the water is not getting out.

[SteveF_911]

I have Webers with watershield air cleaners

Lower tube goes to the crank case vent and the upper one goes to a K&N breather.

[911pcars]

I'd suggest installing a catch tank of some sort between the oil filler tube and the breather to catch/separate oil from vapor. I also suggest returning the blowby into the intake after the catch tank for environmental purposes. You can use anything; from a fancy $100 spun aluminum tank to a used windshield washer tank from your local bone yard. Connect with PCV fittings and hose from the parts store. I've seen track cars with the breather tube pointing into a 12 oz. plastic Minute Maid bottle. It's your car. Make it as nice and functional as you'd like.

Sherwood Lee
http://members.rennlist.org/911pcars

[Mukilteo911]

do you mean PVC pipe or is there a PCV filter of sorts.

[s_wilwerding]

Originally posted by Mukilteo911
do you mean PVC pipe or is there a PCV filter of sorts.

PCV stands for positive crankcase ventilation. It's a valve that allows air into the crankcase.

[911pcars]

911s don't use a PCV valve which normally vents crankcase pressure off idle into the intake. On our engines, it's just a breather hose that normally goes to the air cleaner. The blowby from the crankcase (unburned hydrocarbons) is mixed with oil vapor (sometimes a lot). At high speed and if the oil tank is full, oil mist will finds its way out of the oil tank which ends up dripping on the ground (and engine) on its way out. Racing organizations frown on oil on the track, thus the need for a catch can.

Sherwood

[Mukilteo911]

how about this. Take the crank case tube directly to the air intake to eat up thase fumes, then take the oil off to a catch can with a vent. I would suspect that the oil does not fume much and this would allow for the water vapor to get out.

[911pcars]

The oil breather tube carries both oil fumes and fuel vapors which should be separated otherwise the engine ingests oil. I can't think of an easy way to separate the two inside the air filter housing.

Sherwood