Oil breather catch can plumbing

[Mike Telow]

Would anyone have a photo of a oil breather catch can installed in their GT40?
I picked up a set of repro Gurney Eagle valve covers that need to be opened up for the oil fill and vent and want to make sure I do it right before breaking out the hole saw. I might track the car at some point. Thanks.

 

[EGLITOM]

Dear Mike

this is the way i´ve done it

http://www.gt40s.com/forum/gt40-build-logs/24525-toms-rcr-40-trackracer-24.html#post317270

Use AN12 size hoses and fittings. I used two cans, because together they give the requested volume of at least 1 liter. I also vent the gearbox into one of them.
Also check for access underneath to have the possibility to put a tray underneath to regular empty them ( which i do need, due to probably have to much oil in the engine when the accusump recharges into the engine)- Pay attention to have a splash shield over the vent opening in your valvecovers also to prevent direct spilage.

This are the cans i´ve used
https://www.cantonracingproducts.co...NPT-BOTTOM-PORT-WITH-PETCOCK-FOR-EVAC-SYSTEM/

only added a AN6 bung into one of them for the gearbox breathing.

See here the weld in OIL filler with screw on cap.

I also have a set of those replica covers. I checked them just recently and would do the very same to them. Two AN12 bungs and one filler to weld in. ( they will be added together with the weber conversion)

TOM

 

[Andy Green]

Something like this using AN12 fittings
Regards,
Andy

 

[Mike Telow]

Thanks guys, I have a question, actually 3. Right now I vent into the intake I believe. I am running Webers. Should I run to the can first and then run another line back to the intake, or block the intake off? Do I need to vent both valve covers? Right now only 1 side is vented. Lastly, what is the difference between vented with a filter on top and a closed system and if I'm going to track the car, do they prefer one over the other? Mr. Holden, would you have a picture of your setup on your ERA? I wish I would have snapped a picture when Teddy was showing me your car. Thanks...

 

[Jeff Young]

1. Block the intake off. Venting the crank to the intake is an emissions feature to burn off blowby. No need to do that.

2. On a V8, each cylinder bank is going to have some positive pressure and blow by. I'd vent both.

3. Filter on top means that oil and vapor can escape to the atmosphere. The closed system is better in my opinion in that it traps the oil where you can collect and drain it.

 

[EGLITOM]

3. Filter on top means that oil and vapor can escape to the atmosphere. The closed system is better in my opinion in that it traps the oil where you can collect and drain it.

Tbh did not completly understand the "closed system" question. Somehow you would have to vent to somewhere external to the engine. Otherwise you would build up pressure in this system. How is a closed system working ? or is such system not realy closed and only named this way? Or is a closed system just a system venting into the intake with a catchtank inbetween?

I´ve not seen it on cars engines but a lot of motorcycle engines use a checkvalve in the ventline to the catchtank. The checkvalve is oriented the way that it blocks the air to be sucked back into the crankcase. Therefore a vacuum will be built up in the crankcase. This is said to improve engine performance escpecially at higher RPMs. It is also tobe said that it is most efficient the less cylinders and engine has ( thumpers, twins, tripples) . So i don´t know if it would be worth a try on a V8.

TOM

 

[Jeff Young]

Oh, sorry -- you vent via a guage filter on top of the external catch can.

You put those things on the valve covers and often times you get so much oil in them they leak out.

 

[EGLITOM]

Aahh ok

so basically what i´ve shown above in pictures, is what you describe.

TOM

 

[Randy V]

Venting both sides of a V type engine is not necessary unless you cannot get a large enough line to the vent can. #12 single vent line is fine for most any size engine.

Remember that the V engines - both sides share the same sump. Therefore pressures are equalized there.

 

[Jeff Young]

Randy, a thought on that. Depending on ring wear, you can get different levels of pressure in the heads. I have one large line on one cylinder head and one small on another, and I get some leakage out of the small one.

I understand your point and agree with you that most of the time it is correct, but I could see situations where the blow by in one head is stronger than the other -- am I wrong on that?

 

[Randy V]

Jeff,

I understand what you're saying, but the amount of pressure leakage from the ports past the valve guides is minimal at best, so any contribution to blow-by on the top end is not really a factor. I have no true numbers, but my best guess would be that easily 99% of all blowby gasses are vented from the cylinders into the crankcase.
There are generally quite large oil return paths from the top of the cylinder heads to the lifter valley and ultimately to the crankcase..

You will generally not see crankcase ventilation lines connected to the right side valve covers of circle track cars due to G-forces in the constant left turns.

Smokey Yunick designed a floating ball breather system where both valve covers were joined by a manifold between them at the front of the engine (Chevrolet). The ball would roll to the outside and shut off the ventilation from that side. It worked well, but was found later to be non consequential to the ventilation of an engine in good repair or an engine with a dry sump oiling system.

Hope that helps unravel the spaghetti...

 

[Brett James-McCall]

Andy Green, what did you do on the other side? Have you joined the hoses? I was planning to T mine off somewhere and have one hose going into this: Professional Motorsport Parts, Spares & Rally Equipment from Rally Design Ta

Brett

 

[Andy Green]

Brett,
I'm only venting to the catch tank from one head. My reasoning is that any balancing of breather gases will be done valley of the V8. A lot of production V8 breathers also only vent from one head.

Also I didn't want to fork out the £30 or so for a -12 3-way connector to connect in the other head!!

Regards,
Andy

 

[Brett James-McCall]

Thanks Andy, at the moment I have 2 push on Ford Racing caps that have push on tails. I was going to join them up with a simple T piece. It wouldbe easier to use only one side. How have you blocked the other side please? Thanks

Brett

 

[Andy Green]

Hi Brett,
the other cam cover only has the filler cap in it, so it's not an issue. You could block yours off with a simple ally bung
Regards,
Andy

 

[Bob]

I can see venting both rocker covers, as seen in old photos of NASCAR, Trans-Am, and other engines.
But in an application where the engine doesn't regularly see or manitain extremely high RPM wouldn't the crankcase presure equalize through the pushrod and oil drain back holes?

 

[Andy Green]

Hi Bob,
exactly, that's why I've only vented one cyl head
Regards,
Andy