Hover over a number for the key, click on the menu items below to show the vapour/vacuum routings.
Image from the British Leyland Workshop Manual
When the engine is running carb vacuum is applied via the crankcase breather pipe (14) and oil separator (15) to the crankcase and hence the rocker cover, which has a non-vented oil filler cap (16). A restrictor (10) in the rocker cover vent limits how much air can flow to avoid weakening the mixture excessively. Air is drawn through the purge line (9) via the charcoal adsorption canister (8), vent pipe (11) from the atmosphere. As air is drawn through the charcoal canister previously adsorbed fuel fumes (see Tank Expansion and
Carb Expansion) are given up to be burnt in the engine.