North American Emissions Plumbing - Twin SUs without Anti-Runon Valve

Hover over a number for the key, click on the menu items below to show the vapour/vacuum routings.

Fuel Flow     Tank Expansion/Contraction     Carb Expansion     Crankcase Breathing    

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.