Crankcase Breather Mods

Crankcase Breather Mods

I have a roughly GTS equivalent breather setup on my GT. Louie [Ott] has a much more elegant system to actually separate the oil mist from the crankcase gases before they are disposed of. Actually the standard setup burns the crankcase gas by venting into the throttle body, but Louie found a negative pressure point in his exhaust setup and dumps them straight into the exhaust pipe. He also has a drain down from the separator into the crankcase which was good since he found evidence of enough oil there to make draining the separator manually a regular chore. I think I remember Don Hanson had a modified setup too with a separator, but I think he did just manually drain his when needed.

Back to my setup, it really only requires buying one more valve cover fitting and the long valve cover to valve cover hose standard on the GTS. The fitting is on the order of $20 to $30 and the hose is probably the same, I was being cheap and didn't want to wait for the hose so I fabbed up a copper pipe with half of the GT hose on each end. This would actually cost more than the correct hose if you hadn't already ordered the GT version and waited too long to return it. The diagram in the manual page 24-218 tells what the change was. I did not create a new connection high on the filler neck as in the real GTS but otherwise I just copied the GTS plumbing. I have a write up and some pics on my web site at under the Land Shark link.

Ralph S. Smith

I was away at the track and did not see the original post, but my updated breather system does work really well, now. I think it is similar to the GTS set-up. The original modification was done by Deveks, who did a really tidy job of locating a catch tank behind the wheel inside the left front fender. They installed a plastic catch tank (from one of the race cats, I forget which) with a drain valve and a short hose (to catch the fluid when you open the valve to drain) I think they followed the Porsche routing fairly closely.

My original GT set-up, that routed the breather oil back to burn in the throttle body found me using 1.5 quarts of oil, per track session, both with my stock GT motor, and my Devek big motor. With the new setup, which was essentially a loop from front to rear of each cam cover, connected to each other then taken to the catch tank, I found I was still squirting 1.5 quarts of oil into the tank each track session, or almost 3 quarts during a Nevada highway run! I started using a couple of Amsoil bottles, and just draining the tank after each session and pouring the oil right back into the top of the motor. Right, a hassle!

But to cut to the chase: If you take the vent hose off a high section of the cross over, cam cover to cam cover hose, I find almost no oil collecting in the catch tank now. I surmise the GT/GTS motor does not drain the oil back down quite quickly enough to keep up at sustained high revs. After a period of running hard, the oil level in the vent system fills the vent hoses and the outlet hose becomes a Drain hose, rather than a vent hose. So, taking the outlet hose up high over the engine before going into a catch system(or the throttle body, or an oil separator) prevents the vent system from becoming a siphon. I was totally surprised when I discovered this (by trial and error).

I now drain my catch tank about once a week, and just get a small bit of oil and water(condensation from the motor) each time. I would be interested to have some other GT owner try this, to see if the fairly wide-spread "Oil thirst" of the GT is really just a plumbing mistake by Porsche engineers in the breather system design.

Don Hanson

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