X/F: Why does oil blow out of my catch tank breather?

[virden]

I have a wet sump 1700 X/F  which I upgraded by adding a catch tank to the front of the passenger foot well, it has two inlets at the top of the cylinder and a breather on top end, from which a pipe leads down  to within a couple inches of the road.  At first fitting I had a mini air filter instead of the pipe, but suffered from fumes in the cockpit.   Input to the tank is from the lower crankcase and the cap on the rocker cover, both inlets have a small internal pipe ending just above the tank bottom. Very little oil collects in the tank with most spraying the underside of the car or leaving a pool when the car is parked.  Oil consumption is relatively light and appears the same as before the upgrade.

Q1.  Have I misfitted something?

Q2. If I stuff course wire wool or kitchen scourers in the tank will this help retain the oil?

[randybugger]

Are you sure oil isn’t coming out from somewhere else?

are you using the original fitting in the crank case? Have a wipe around and see if it’s venting there where the pipe pushes in rather than into the tank.

[virden]

 Yes I am sure, that is she does leak a little, but its just a light coating at front of the sump.   The crankcase elbow is a Burton unit and leak free. The catch tank has very little oil in it, but the breather pipe leaves  a small pool each timeethe car stops

[randybugger]

Oil must be misting in the pipe, collecting and then leaks out as you’ve got it lower than the tank. I guess you could try wire wool in the top of the tank to try and collect the oil droplets.

 

was the fumes really that bad? Mine vents in the engine bay and I hardly notice it 

[pugwash]

Try shortening the two pipes that go into the catch tank so they are half way down the tank.  On my sigma engined car with catch tank I led the input pipes right to the bottom of the catch tank and had the same problem of misting going everywhere from the exit pipe.  I found that as soon as I had anything in the catch tank I was then “blowing bubbles” through the contents of the catch tank and creating a mist that exited through the vent pipe.  As soon as I shortened them the problem went away.

[Nick T]

All cross flows (in my humble opinion) "breathe" more than the modern engines (well mine did). If you are getting very little oil carry over to the catch tank then everything should be fine. It might be worth carrying out a compression test just to be sure.

 

 

cheers

 

Nick

[DaveMorris]

The recommended (Roger King) routing for breather pipes for X-flow was, I believe, from crankcase breather to rocker cover somewhere between the two carbs, and then outlet pipe to catch tank coming from rear of rocker cover. 

This might be for a dry-sumped engine, though I can't se why it would not apply to a wet sumped engine.

Dave.

[Roger King]

That is indeed for a wet sump engine. A dry sump engine has no need of the crankcase breather because the scavenge pump removes any excess pressure from the bottom of the engine.

[virden]

 I half filled the catch tank with wire wool, shortened the internal pipes and changed the outlet from a pipe that led down to near the road surface for  an air filter. This has stopped the leakage onto the road, and there are no detectable fumes, but the tank is filling at a rate of about 60ml per 100 miles. Is this acceptable?

As to  following Roger's recommendation of feeding the crankcase outlet into the rocker cover, I  believe this is supposed to be introduced between cylinders 2&3, but I cannot see how this can be done on my car as the accelerator spring, cast alloy rocker box and heater pipe leave little room for an elbow, or does the pipe run another way?

[Roger King]

It doesn't really matter where the pipe is introduced into the rocker cover so long as it isn't close to the rear breather outlet leading to the catch tank.