Hitachi Twin Carb A12T

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A12T is the twin carb engine fitted to Datsun Sunny B210 and Nissan Cherry PE10. It uses the Hitachi Twin Carb system, dual 38mm Hitachi sidedrafts. These mainly differ from the A12GX Engine Hitachis in that they are have a new idle speed and idle mixture system. They can be easily distinguished by their flat tops.

Overview

JDM 1973-1975 B210 GX models had either an A12S (single-carb) or optional A12T (twin-carb) engine. While the A12T is very similar to the A12 GX Engine, it used different flattop Hitachis and a slightly different intake manifold with a few more fittings. These are good carburetors that are not jetted leaner, but instead have a closed fuel bowl vent system. They are almost identical to the dome-top carburetors except for the IMS fittings on the top of the carbs. They total system (inlet manifold and hoses) is more complicated to allow idle mixture and speed adjustments and capture all the gasoline fumes into the air cleaner.

JDM Datsun Cherry (E10) models also used the A12T engine, including the famous Cherry X1-R vehicle.

= Competition Flat-Tops

NOTE: Competition versions of flat-tops do not have IMS. 
They are simply the old style carbs with the new tops.

Datsun Competition (Nissan Competition) sold a open-vented, non-IMS, system:

Supplied with simple vent tubes. Production A12T vents the carburetors to the air cleaner.

Idle Mixture System

Ummm... smells good, and works good too. JDM non-competition (stock) Hitachi sidedraft flat-top carburetors come with an advanced Idle Mixture System (IMS), for fine tuning of the idle mixture.

Thick hoses: Idle Mixture System (IMS)

Idle Mixture System

IMS body with Mixture Screw

Adjustments

Idle mixture (IMS) is possible with the new flat-top Hitachi design.

Green: Hoses to air cleaner (including the curved IMS hose)

Blue: Fuel lines to fuel bowls
Red: Idle speed system (air bypass system), connects to IMS body vents

Blue: Fuel bowl vent lines
Green: IMS inner vent line (to Air Cleaner)

Red: IMS (Idle Mixture)

Hitachi Twin Carb Twin Carb Overview A12GX Engine : A12T (B210) : A14T Hitachi Twin Carb Adjustment/Tuning Engine Photos A12GX : A12T : A14T : Unsorted Carburetor Part Numbers A12GX parts : A12T parts : A14T parts