LS1 Breather setup

[Aussie Mike]

Hi All,

I had an enjoyable weekend in the shed getting the car ready for the AROCC 6 hour in 2 weeks.

I pulled my LS6 manifold to put the 4 barrel setup back on and was greeted by the usual oil around the intake ports. I'd been thinking about building a better breather setup for a while and this fired me up.

I built a combination catch tank and engine breather. I'm not using the PCV system at all now. I figure it wasn't that environmentally friendly to burn all that oil when you could just drain it every now and then and pour it back in the motor.

The catch tank breather holds 3.5 Litres so it doubles as an oveflow for the engine in case of some catastrophic failure. I don't fancy having oil dumped on the track.

Phil Mizzi gave me the idea for the breather tank but I figured I'd make it out of tube rather than a box as it was easier to fabricate.





I'm pretty happy with how it's turned out. I'm even more happy because I'm finally starting to get some good results welding aluminium with my TIG. I'd been struggling to get the setup and technique right. I'd been getting good results with steel and stainless but aluminium had been a real pain. I think the turning point might have been the new automatic welding helment I bought. It's a really good professional one with a very clear lense and good controls for different shades and response time etc. It makes it so much better being able to see what your doing. Aluminium doesn't change colour when it's molten so you have to watch the weld pool closely to see it go shiny when it's molten. I just couldn't see that clearly with my old helmet.

Hope you all had fun weekends.

Cheers

[LoBelly]

neat


(how does the oil know where to go?)

LoBelly

[boxhead]

The prettiest part of all those pictures Mike is seeing that VIN number.

[Plums]

Very nice Mike... Some great work there

Are you going to fit a tap/valve to the bottom with a line back to the engine or just empty it manually???

[Aussie Mike]

The bottom of the tank is cut on an angle and an AN#6 fitting welded on at the lowest point. This will have a cap on it. It's positioned so you can just put a pan under the car and it will drain straight into it (no chassis parts in the way). I thought about plumbing it back into the motor but figured a drain was a lot easier. If it was a daily driver car I'd probably plumb it back in.

Where does the oil go? Well the two pipes on the top of the valey plate take air from the crank case and rout it to the breather tank. There's a baffle setup inside the breather tank that helps to seperate the oil mist out of the vented air. The seperated oil collects in the bottom of the tank. You would check the level from time to time by removing the filter on the top and having a look inside and draining when nescecary. Phil N reckoned he collected about 300-400Mls over the nationals in his setup.

Normally this venting would be ducted back to the air intake of engine. Oil vapor would be burned along with the fuel and air. One of the side effects of burning this oil is that it drops the octane rating of you fuel air mix. That oil also cokes up the inside of your engine over time.

Cheers

[Rebel1]

Mike, I too wonder how the oil vapor knows where to do.

I understand that usually a catch can would plumb the crank case pressure to a vacuum source. ie intake manifold.

What causes your crankcase pressure to vent thru your catch can?.

Maybe I'm thinking wrong which is highly probable.

[Plums]

When the engine is under load there is generally positive crankcase pressure, (even the best built engine will experience a small amount of blowby). This pressure will escape anywhere it can, valve stems, engine seals etc. but preferably into your fancy new catch can set-up.

[Rebel1]

Yeppers, I understand that Plums.

But it seems that Mikes catch can is plumbed so that both the inlet and outlet is receiving the came crankcase pressure.

I notice on the holden forums that many use a catch can to collect oil vapor to prevent contamination of the inlet manifold but usually the feed is from the crankcase/tappet cover (same pressure) to a catch can, then to the inlet manifold.

The object being to collect most of the oil vapor before it can contaminate the inlet.

Maybe there is some weird science going on that I don't know about. (highly likely)

Ahhh edit......the pressure is venting out the gauze/breather....got it. No recirculation...just venting and catching ).

[Aussie Mike]

The 2 vents off the valley cover are as close as you can get to the crank case without drilling a hole in the side of the block. All the venting on the rocker covers will be sealed. There's no where else for the crank case pressure to go but into the breather tank.

As Bobby was saying there is usually positive pressure in the crank case because of leak down from the combustion process. It needs to be vented freely out of the engine. Any build up in crank case pressure will affect ring seal and also try and pump your engine oil out of the front and rear main seals

It's usually achieved in most motors using engine vaccume and a 3/8" hose connected to a rocker cover. Without vaccum giving it a helping hand you need some larger pipes to ensure no restriction hence the 2x 5/8" hoses. Both of those pipes are outlets. The system vents to atmosphere via the air filter on the top of the tank.

Cheers

[Aussie Mike]

Originally Posted by boxhead

The prettiest part of all those pictures Mike is seeing that VIN number.

It makes me smile too.