The 1275cc crankcase breather system varies by carburettor specification, and the correct components must be matched to the carburettor variant fitted to the car. Three distinct configurations were used across the 1275cc range.
Non-Ventilated Breather (12CC)
Cars fitted with the earliest AUD136 carburettors (non-ventilated, on 12CC engines) used a simpler breather arrangement. These carburettors have no breather hose union on the body, and crankcase gases are vented through the oil filler cap and a road draught tube. An emission control valve assembly on the inlet manifold (the earlier manifold with tapped boss, part number 12G583) regulated the gas flow.
1275cc Breather System Identification
From the introduction of ventilated carburettors, AUD327 on 12CE, 12V586F, and 12V588F engines, and AUD662 on 12V778F engines, the breather system was revised to route gases from a separator canister on the timing cover through a Y-piece and individual hoses to each carburettor body. The gases enter through unions on the carburettor bodies and are drawn into the inlet air stream by manifold vacuum. The hose sizes, connector types, and routing differ between the AUD327 and AUD662 configurations, so the carburettor tag number should be quoted when ordering breather components.