Crankcase Breathing System - Late SIII

[jac04]

OK, Tim & Kevin were over last night picking up some parts and they were checking out my Lightweight. Kevin noted that the breather system seemed a bit odd. Now that I'm thinking about it, it seems a little strange to me as well. I figured that I would open this topic up for discussion.

The vehicle is a late Series 3, and when I purchased it, it had the same exact breather set-up that it has now. I have no oil fill tube on the side of the block - oil is added through the top of the valve cover. There is only one breather in the valve cover. This breather is connected with a "T" to both the intake elbow and the carburetor base adapter. At idle (high manifold vacuum) I would think that this would allow air to bypass the carburetor - creating essentially a vacuum leak. Now, the hose going to the carb adapter is quite small compared to the others and the opening in the carb adapter is very small as well. Maybe this is acting as an orifice and restricting flow. I don't know. Comments?

However, the factory manual clearly shows my arrangement for late vehicles. Refer to Figure 3 in the pictures below. So, the factory obviously designed this system and it should be OK.

Has anyone else used this breather arrangement? Is there any reason I should consider going back to the 'older' style breather system as shown in Figure 2?

http://i79.photobucket.com/albums/j126/jac04/000_1815.jpg

My set-up:
http://i79.photobucket.com/albums/j126/jac04/000_1817.jpg

http://i79.photobucket.com/albums/j126/jac04/000_1820.jpg

[jac04]

Hmm...seems that this is what's called a fixed orifice pcv system:

http://i79.photobucket.com/albums/j126/jac04/PCVSystem-fixedorifice.jpg

[jac04]

Well, I guess I'm answering my own questions, but maybe this will be of interest....

The system does use an orifice adapter in the carb adapter, shown as ERC2875 in the attached picture. I have verified that this adapter is fitted. So, this is definitely a fixed orifice system and it appears to be in correct order.

http://i79.photobucket.com/albums/j126/jac04/PCVSysyem.jpg

[Moose]

The engine in my Series 3 88 for the past 12 years or so came out of a 1982 Ex-Mil 109 and has exactly the same set up as yours, including the fixed orifice. It's always been set up like this and I have never had any drivability issues with it. Brett

[jac04]

Thanks for the feedback. It's nice to confirm all this.

[ybt502r]

My SIII looks exactly the same. I bought it years ago in the UK from a solid outfit that works on and rebuilds Rovers, especially Series trucks. I assume they knew what they were doing when it was updated. Other than replace the breather at one point, I've never messed with it. Seems to run quite sweetly (at least as far as the crankcase ventilation system has anything to do with it).