Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Workshop Note - GDI Oil Breather

This modification was done by SteveT a long time ago, and has been done in one form or another by other GDI owners. The purpose is to intercept crankcase vapours before they hit the inlet valves, where deposits can build up over time.

I always try to do these mods so that they can be reversed, and that they look like a factory fitted item.

For now I'm keeping the closed crankcase system, but with a catch tank, and I'll see how this goes.

Catch tanks are available from performance specialists, and there's a decent choice. I went for an aluminium one to fit into the 'underbonnet scheme'.

The inlets on the tank are 13mm, but the outlet from the cam cover is about 15mm, so a bit of sleeving is needed to get a good seal.

I got the rubber pipe from e-bay and played safe by getting half a metre of both bore sizes.



I made up an aluminium bracket which fastens to the two bolts which also fix my heat shield and the two engine cover stays. The back is lined with Reflect-a-Cool.



This is how it fits.......





Here the original breather hose goes to the left hand connection. It's unmodified so can be put back if required.
The hose on the right hand connection with two red stripes curls under like a pigs tail, and I managed to fit this to the breather on the cam cover. This is 13mm inside diameter and is a tight fit!

thanks for that dave...

I like the heatshield over the manifold and the heat shield on the air inlet pipe. What you have done with the rocker breather is just fine, looks neat, and will do no harm. Sadly it is not the main cause of inlet valve/ inlet tract fouling. Mr Ford in his infinite wisdom also runs second breather pipe to the underside of the inlet manifold from the crankcase. For some reason I cannot put a pic of the pipe in this post (I keep getting a massage saying it's over one meg but it's only 300k)so I'll put it in the Morgan Gallery. To stop the crankcase vapours properly (which is a VERY good idea) you need to trace this pipe and remove it from the crankcase. Remove the "anti-backfire" one way pcv valve if fitted (which is actually just a ball bearing and a spring in a tube) and replace the tube in the crankcase, running it to atmosphere or a catch tank as is your want. Then do not forget to plug the inlet in the manifold. Hope this helps.

Useful info Griffo. If you use the TM image server instead of the uploader, you can put pictures up to 8MB into threads.

See http://www.tm-img.com/ifu

Thanks Griffo, I'll take a look at that next!

Interesting to see how it goes Dave.. I removed my set up when I sold my Gdi. I fitted a one way valve with a filter as well as a catch can. After several thousand miles it had nothing in the trap and the filter element was still white and clean. I put it back to standard.

I suspect you won't find a lot in yours..

This is a very timely post for me as I am contemplating fitting an oil catch can to my GDI when I eventually pluck up the courage.
Regarding Griffo's post, would the answer be to buy a 3 port catch can? Presumably there are 2 inlet (dirty)and 1 outlet (clean)on said can.
An alternative perhaps is to squirt a can of CRC GDI intake valve cleaner into the throttle body every so often.

I've yet to inspect the inlet manifold side John. The cam cover oil trap which I just did is an easy mod and is reversible. The thing is, there isn't much space for the can on the nearside. So mine has a shortish pipe from the cam cover into the catch can, with the long original pipe which runs behind the engine and tees into the air feed pipe just ahead of the throttle body.

So with the can on the offside it would be untidy to route the crankcase pipe all the way across. So a three port catch tank is best mounted nesr the throttle body on the nearside.

I may just vent the crank to atmosphere and block the inlet manifold but I would like it to look factory. I'm going in tomorrow for a recce

I agree Dave, I can find nowhere to mount it on the offside. I have read that the lower the better and cooler the better so I am thinking of mounting on a strip of L shaped alloy mounted through one of the many holes in the chassis in front of the washer bottle.

I think all these are good ideas but, just a few thoughts:
- The only people who benefit from catch cans are people who sell catch cans.
- You can make one up yourself from any type of container -- just vent the can to atmosphere. Do not run it back into the inlet manifold because even the most expensive catch can will only reduce inlet fouling -- not eliminate it.
- The most important thing is that the crankcase has unimpeded ventilation. The older and more worn an engine becomes the more important this is since "blowby" is likely to increase.
- With dry sump engines and racing clearances crankcase venting sometimes has to reverse and allow atmosphere to be sucked into the crankcase to allow scavenge pumps to work properly. This latter observation is I admit something of a disabling dichotomy for those of us who play around with Morgans.