Oil catch cans
 

I suspect my greasy plugs and sticky internals in the intake are being caused by my valve cover breather setup.

Ive got non baffled covers, one with just a breather and the other a breather that has a vacuum line running to the intake manifold. No pcv valve at all.

So my options are:

Buy new higher rocker covers with baffles (as there's bugger all clearance above the rockers now).

Squeeze in a baffled gommet ( just disovered those from Moroso)

Put a catch can in the vac line between the breather and intake.

Your thoughts on whats gone work best or any other ideas....do i need a pcv
valve in there somewhere?

Do you need the vacuum the draw out the blowby or just ditch that and let the catch can vent to atmosphere?

Thanks

Greg PCV's have been mandatory since Noah started in the 1st XI.
They are a good thing and they work. Give one a shot it'll help

Had the same problem on my 289 ( with standard size valve covers), especially when I did sprints and regularity track days. Had catch can with lines from both valve covers (both with pcv) going into it, still had blowback , then fixed the problem with running both lines into one then into catch can inlet and a vacuum line from outlet on the can to either manifold or carby vacuum. After a hard workout on the track I empty catch can which usually has about 100ml oil.
Never had the problem when just doing normal driving on the road.

Thanks, I'll try the pcv then vac lines to manifold via catch can...........then I've got it all covered:)

I am supprised that there is such little response, I would have thought that there would have been a variety of set ups to share.

Does that mean that you can't just run a breather from the rocker cover to the aircleaner?
JD

That would be a Yes-----you can't !

that's what I thought......maybe nobody likes me:CRY:

Here's what I did on my old car...

A couple of sealed breathers on the covers,with braided hose running up to a collection tank,with a good breather fitted on the top of it.

The tank had a tap to drain it,but it never got much in it,the oil mostly just blew up the braided hose,and ran back into the engine when racing.

The tank was also stuffed with steel wool to stop any slosh of oil if it collected any.

It worked really well, and it gave me something extra to polish !!

Then I stuck my "cobra nationals badges" on it.......FANCY !

Cheers,
Warren
http://www.clubcobra.com/photopost/d...m/100_4766.JPG

So, Wazza yours did not have a vacuum hose.

What i'm trying to determine is, do the vapors need to be drawn into the tank using manifold vacuum or do they find there own way there?

It's not the vapors that are the issue, it's crank case pressurization that you are trying to avoid.

Your engine is a pump with it's pistons going up and down. There is air being displaced from one cylinder to another inside the crank case. Your combustion pressure on the top of the piston is held in there by the seal of your valves and the seal of the rings. Your piston rings are designed with a taper in the back that lets the combustion pressure help push them out against the cylinder walls for a better seal.

That seal is never perfect so some of that combustion pressure leaks past and into the crank case. This is commonly know as blow by. It's not a problem but needs to be managed. If that leaked pressure from your combustion cant get out of the crank case you will build up positive pressure and start pushing the oil out of every gap it can find. The other bad thing crank case pressure does is act against that combustion pressure doing it's job pushing the rings against the cylinder walls for a better seal.

The PCV (Positive Crankcase Ventilation) valve was invented to combat that. By using engine vacuum any excess crank case pressure is drawn off into the intake. Ideally it will run with some negative pressure in the crank case helping the ring seal. It was also an early emissions device as it draws off any oil vapor and combustion gasses to be burned in the motor rather than venting to atmosphere.

The downside of this is that depending on how efficient the oil separator is you could be burning oil vapor in your combustion chamber which lowers the effective octane rating of the fuel.

I prefer venting to atmosphere but the important thing here is flow. There is no engine vacuum to help draw off that pressure so breathers or hoses to breather tanks /catch cans need to be be a good size.

My setup currently has a large catch can oil separator that is baffled internally. This is vented to atmosphere by a filter breather. The can is connected to the crank case via the valley plate via 2x AN#10. I chose the valley rather than the rocker covers as I figured there may be less oil vapor washing around in there than the valve covers. The bottom of the tank has another fitting with a 1 way check valve to allow collected oil to drain back to the sump on it's own.

Not saying it's ideal but it's the way I thought I'd try.

http://www.clubcobra.com/photopost/d...iller_cap2.jpg

Cheers

I run an LS1, so no oil breather issues, its only those boat anchors that give problems.

:confused:

OK, I have a dumb question. I am running fuel injection with no place to hook a line for vacuum to pull vapors and pressure out of the oil pan. I was thinking of getting two of the oil caps that plug into the valve covers and running hoses from them to a small catch can. But would that relieve the pressure?

Also second really dumb question. On a PCV Valve does it require a vacuum to open it or will the pressure push it open. I thought that it required a vacuum to open it and pull the vapors through.

Thanks,

Ron

Thanks for that detailed explanation Mike, I've read many online and that's the clearest:)

I'm off the fleabay to get a few goodies.

Hey Boxy, thanks for your input:p, BTW isn't Mikes' an LS1 %/

Early LS motors like mine did have a few oil problems. I believe they run quite low tension on the rings so had a bit more blow by till well broken in. This made for a lot of oil vapor being pumped into the intake. When I pulled the manifold the ports were quite wet.

You may remember some complaints early on from Holden owners about their oil consumption.

The LS has gone through several generations of breather setup to combat the oil going into the intake. When I built this I just figured I'd eliminate it all together.

Cheers

Just dry sump it Greg... Stops all your problems....

The PCV does need vacuum to pull it open or some positive pressure on the underside to push it open. They are a 1 way check valve that usually has a light weight spring to keep them closed or are oriented so that gravity keeps it closed.

Cheers

would you STOP encouraging me to spend more bluddy money Ash.......I only just bolted on a new Moroso high cap sump and swinging pickup