Passenger side valve cover should have a breather at the front. It has a large black hose that leeds to a Y and then into the sides of the carbs. The drivers side should have the oil fill and riser at the front. At the rear, there is a breather nipple. It has a small bore because it is attached to a vacuum port on the drivers side carb. It first travels thru a one way check and the charcoal canister mounted where the TR7 battery tray is. The small nipple requires a vacuum in order to do it's job. The other breather has a larger bore and doesn't require much vaccum at all. The Rover V8 develops alot of crankcase pressure. A simple breather that is not hooked to a vacuum may not be enough if the motor sees sustained high RPMs.
One time I was caravaning with Woody and a couple of other TR8s up to Stowe. We stopped at a rest area just inside Vt. The fella who was with me(he is a police officer) could not find his wallet when we got back to our cars. Everybody took off and left my friend and I to look for the wallet. 15 minutes later, we found it between the seat and the rocker. It was 6 AM on a Sunday morn. The other guys had a 15 minute head start and they drive fast. We had some serious catching up to do. I don't want to say how fast we were traveling, but we caught up to them in less than 20 minutes. Let's just say even the early speedo's don't go that high. Well long story short, when we got to Stowe, my engine had oil all over it because of the breather set up I had. My car happened to be for sale that weekend, and the police officer I was with, wrote me a check for the car the following Monday. His brother still owns that TR8. So, if you ever decide to unleash the car's potential, you better have a breather hooked up to a vacuum port.