Self-Circulating catch can.

here is my design for a Self-Circulating catch can. this was designed with my friends LS1 in mind, but it could work on any engine, including SBC...

the only downside to using this is the loss of your low oil sensor. (or in the case of 3rdgens, tapping a second hole in the oil pan.)

basicly, the air/oil mist is seperated by a stainess steel mesh, much like other catch cans. the diff is, the bottom of this can actually has a one way valve, that allows the oil to drain back into the pan once the engine is off.



im open to comments and suggestions on the idea.. im building the first prototype right now in my spare time.

 

Why bother with the valve?

 

the valve is needed so that oil from the pan isnt sucked back up into the can, and so that when the bottom part going to the pan sees air, the PCV only sucks air from the intended source.

 

I'm still not entirely convinced it's necessary, but I don't feel like devoting the brain cells to explaining why right now. Maybe later tonight.

 

It makes sense to me that you'd need the valve. Since full manifold vacuum will be applied to the top of the can, you need to seal the drain so that the engine doesn't just suck up whatever's there (whether it be oil or air.) Unhook your brake booster and stick the hose in a bottle of oil and see how she runs.

LS1 cars are known for sucking down as much as 1/2 quart of oil between changes. The inside of the intake gets nasty and it carbons up the valves. This is a mod that I've been meaning to do to my fiance's 2000 but I just haven't gotten around to it yet.


MrDude....why return it to the oilpan? I can see it with an LS1 because the hole is already there, but for an old SBC why not drill a hole in the top of the valve cover and use a bulkhead fitting? It would mean less plumbing and you wouldn't have to worry about keeping the pipe/tube/hose off the exhaust.

 

Thanks for explaining that.........MrDude the design looks good but I was sorta lost at why...... makes sense now

 

The only thing I see that would be a problem with that is it would limit you to mounting it higher than the valve cover

 

Your example isn't valid. Sure if you stick a vacuum line in a bottle of oil you'll suck up oil, but put a hole in that vacuum line and you won't get anything but air.

Even if the return line is below the oil level, the vacuum will draw in air through the PCV line. The only way you'll draw oil is if the PCV line is blocked.

 

You will if it's a small enough hole.

The PCV is a controlled orifice, not just a pass-through fitting. It will only allow a small amount of air through, which means there is still a large amount of suction present on the vacuum side of the valve. The PCV won't even come close to matching the flow capacity of the 3/8" hose going to it, so you will still get some oil being sucked up through the can.

Try it this way: Put a T fitting on the suction side of your PCV valve and stick a hose from THAT into a bottle of oil. It'll smoke like a freight train.

And what happens if the PCV clogs? I personally don't want to suck all but one quart of my engine oil down the intake.



flrtin1 - The PCV valve is on top of the valve cover anyway, and the hose goes from there up to the intake. There's no reason to mount it any lower.

 

Oil is considerably more dense than air. You're not going to suck up any oil unless the PCV clogs, which it won't if you maintain it properly. If you put the drain into the fuel pump block-off, or somewhere else well above the level of the oil in the pan, you're not going to suck up any oil at all, even if the PCV is entirely clogged.

 

True, but then you have a vacuum leak the size of the return hose.

Like I said, the PCV is a controlled orifice. Even if it's functioning perfectly you still have full manifold vacuum at the catch can. Nothing in the world will change that, except eliminating the can altogether. If you don't put a check valve on the return it will suck SOMETHING up. Whether it's oil or unmetered air doesn't matter, it's still not something you want in the intake.

 

That's why you put the catch can before the PCV valve.

 

So this catch can is to "filter" out oil vapor/oil from the PVC vacuum line?