![[Datsun 1200 encyclopedia]](/wiki/upload/wiki.png)
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 have a new idle speed and idle mixture system. They can be easily distinguished by their flat tops.
|  |
Contents |
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. The 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 X-1R vehicle.
Sources
The A12T twin carb engine was fitted to Datsun Sunny B210 and Nissan Cherry PE10.
1973-1977 Sunny B210 GX option engine (normal B210 GX was fitted with a single-carb engine)
Cherry X-1R
Manifolds
Like the A12 GX engine, the A12T in the B210 used a dual-outlet divorced exhaust manifold.
However, the #Inlet Manifold was updated with two additional connection ports.
Inlet Manifold
A12GX vs A12T: Manifolds are nearly identical, but A12T has two extra fittings
A12GX
Center fitting (yellow arrow) is for IMS speed screw assembly.
Far left fitting (no arrow) is for power brake booster. NOTE: Early Nissan Cherry A12T may be missing this fitting
A12T/A12GX versus A14T Port Sizes
* A12T: 30x35 mm
* A14T: 28x34 mm
A14T identification
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 are for 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. This is a better system than the older style GX carbs, but requires a new way of adjustment.
- First of all, check the ignition timing and set it correctly
- Next, check the float levels. Nothing will work correctly if this is off
- Check oil damper level, and top off with 10W-30 if needed
- Loosen balance adjusting screw completely
- Set idle speed to 750 rpm by turning idle speed screw
- Clockwise: speed decreases
- Anti-clockwise: speed increase
- Synchronize the twin carbs by turning Balance screw
- Turn Mixture screw back and forth until best lean idle is achieved
- Reset idle speed to 750 rpm
- Lean out Mixture until speed drops to 725 rpm
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)Competition Flat-Tops
Datsun Competition (Nissan Competition) sold a open-vented, non-IMS, twin carb system.
NOTE: Competition versions of flat-tops do not have IMS. They are simply the old style carbs with the new tops.
Competition flat-tops are Similar (or the same) as the Datsun 810 SSS twin carbs (200B or Euro 810 carbs).