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Some Datsuns were fitted with sidedraft carburetors right from the factory. Usually fitted with twin Hitachi variable venturi carburetors which are very similar to S.U. Skinners_Unionᵂ) carburettors from Britain. The Datsun 1200 GX models were fitted with twin Hitachi HJE38W 38 mm carburetors. Some Japan-market B210s were fitted with A12T or A14T engines which also used twin-Hitachi carbs. Many Datsun fans refer to the Hitachis sidedraughts as "SUs", so keep that in mind when you read information. It may be about the factory Hitachi sidedrafts, or it may be about the (non-Datsun) British SU sidedrafts.
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Overview
ヒタチ ツイン キャブレター
Reportedly, Hitachi licensed the SU design, but I have yet to see a reference for that (Nissan manual, etc).
Datsun twin-carb setups used two basic Hitachi sizes:
- 38 mm (1-1/2 inch bore) on most cars
- #46 mm (1-7/8 inch bore) on Z-cars 2000 Roadsters. These are too big for Nissan A engines (even if you use one) and reportedly the late model (1974) flat top 46s are not an optimum design.
Identification
Hitachi Twin Carbs can be broadly broken down by:
* Dome-tops (1973 and older cars) * Flat-tops (1974 and newer cars) * Triangular-inlet Choked-carbs (A14.B210 & 260Z)
And by two sizes:
* 38mm bore size * 46mm bore size (six-cylinder Datsuns)
A12 GX carbs are dome-tops
A12T have flat-top carbs with IMS hoses connecting them
Nissan Competition carbs are flat-top carbs without IMS
A14T carbs can be identified by the triangular bolt pattern and 38mm bore.
NOTE: 260Z carbs also look like this but are 46mm bore.
Unfortunately Hitachi ID markings are inked (not stamped) onto the float bowl housing.
Other identifying features include shape of tops, type of fittings, etc.
Three Different Designs
Factory Hitachi setups for A-series engine include the A12GX, A12T and A14T types. These were fitted to JDM B110, B210 and Datsun Cherry vehicles. South Africa also sold many Twin-Carb B110s.
- A12GX for B110 (1971-1973) - Extra Large Oval Ports (30 x 34.5 mm)
- A12T for B210 (1974-1975) - Extra Large Oval Ports
- A14T for B210 (1976-1978) - Standard Oval Ports (28 x 34 mm)
A12 twin carb manifold on A15 engine causes a port-mismatch due to small A15 ports, but even so runs OK
A12 GX Engine
The Datsun 1200 GX (Grand Luxe Twin-carb) models were always fitted with the A12 GX Engine. This engine featured a matched pair of left- and right- hand Hitachi HJE38W sidedraft carbs. These are the true "dome-top" Hitachis, already setup for performance. They can use standard SU needles so tuning it quite easy.
Float chambers have a banjo type fitting for the overflow/breather.
11041-H2300 HEAD ASSY-CYLINDER A12 GX B110
Note: A12GX was not fitted with flat-top carburetors (except 1973-1975 in South Africa).
A12T Engine
JDM 1973-1975 B210 GX models came with A12S single-carb engine OR A12T twin-carb engine. While very similar to the A12 GX Engine, the A12T engine used flat-top Hitachis and a slightly different intake manifold with a few more fittings. These are decent carburetors and (contrary to talk) are not watered-down "emission carbs".
Float chambers used a pressed in brass hose barb for the overflow/breather hoses.
Flat-tops from A12T
NOTE: B210 "GX" (Grand Luxury) refers to the car. B210 GX does not mean the car included a twin-carb engine as the B110 GX did. While some 1973-1975 Japan-market B210 GX models did include the A12T engine, most were fitted with a single-carb (A12S) engine.
JDM Datsun Cherry (E10) models also used the A12T engine, including the famous Cherry X1-R vehicle.
A14T Engine
Starting in July 1976, the B210's A12T was replaced by the A14T. This corresponded with the B211 model change (B210 minor facelift).
These carburetors can readily be identified because they have round automatic chokes on the sides, just like a downdraft carburetor.
A14T engines used flat-top carbs, heavily modified from the A12 type Hitachis apparently to manage emission control.
Some (but not all) GX models used the Twin-carb engine; even in Japan other 1976-1978 GX models used a single carb engine. Unlike the A12GX and A12T engines with their monster intake ports, the A14T used standard A14 oval ports (28x34 mm), which are smaller than A12GX ports (30x35mm).
- A14T Manifold matches standard A14 gasket
- One improvement over the A12GX engine is that the A14T uses a small thermostat where the water goes into the manifold
Nissan B211 Parts catalog showing some GX models were fitted with single-carb (A14S) engine:
A14T Features:
- Normal oval-ports (instead of the large GX size)
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- A lot of emission controls
- EGR port on top of manifold
- Throttle servo
- Flat-top triangular-bell Hitachis
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- Automatic chokes (electric)
- Vacuum ports on each end, top of manifold
- No PCV valve fitting
Carb side:
- 4-bolt pattern on 3.5 in. circle
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- 1.5 inch bore
- Carb spacing approx 7-1/8 inch
- Water ports at bottom
Electric Choke
- the electric choke makes the engine easy to operate & improves emissions compared to drivers who leave a manual choke on too long
- The small vacuum motor on each carb is the choke pull-off. Otherwise A14T carburetors have the same number of fittings as the 1973-1975 A12T twin carbs
SU manifold | A14T manifold
There are British SU carbs which will bolt to the A14T manifold using 2 of the bolt holes on the diagonal of each flange. Maximum parts availability and tunability.
Retro-fitting
For true bolt on experience, you will need a complete setup:
- Intake manifold
- Exhaust manifold (twin down-pipe cast headers). The clearance differently than regular manifolds
- Two carbs
- Fuel lines
- Accelerator cable & linkage
- Choke cables
- Hitachi Twin Carb Air Cleaners
In general on a given manifold you can use SU, Zenith-Stromberg (ZS) or Hitachi sidedrafts, but note that the linkage, hose locations and air cleaner attachment will vary.
NOTE: The Hitachi sidedraught carbs are on the left side of the A-series engine. On a RHD car there is clearance aplenty, but on a LHD car fitting an air cleaner it a bit tricky. But this is more easily fitted to LHD than a twin-Weber setup.
Variations
For a list of Part Numbers, see Hitachi Twin Carb Part Numbers
Parts Donors
* A-series import engines from Japan * Datsun Competition setups * Datsun 411 SSS (circa 1966) * Datsun 510 (1600) SSS * Datsun 610 (180B) SSS * Datsun 710 (160J) SSS * Datsun Roadsters
Reportedly, all Roadsters were fitted with Hitachis except the 2000 Roadster (2-liter engine) which came with Mikuni/Solex carbs.
Damper Oil
The damper (aka dashpot) is oil-filled. Nissan recommended 20W or 10W30 Elephant Oil, but any brand of motor oil will work. Others have reported success with ATF (automatic transmission fluid), sewing machine oil (generally 10W), or motorcyle oil. The lighter oils tend to run the carb on the lean side.
Tuning
See main article: Hitachi Twin Carb Adjustment
Troubleshooting
Go here for lots of information: The Hitachi-SU Tech Pages - Troubleshooting.
References
* Nissan Motorsports catalog (#99996-CAT98 and other years) * Nissan Schematic catalog (#99996-M8015) * Nissan Datsun 1200 Model B110 parts catalogs
Parts Suppliers
- Nissan sells quite a few parts for the Hitachis
- Z-Therapy sells parts and complete setups http://www.ztherapy.com
- Get the 510 SSS carb setup. The jetting is slightly different but otherwise they are the same
- craigslist and other local sources (from time to time)
- eBay from time to time
The parts although not common, are not rare in USA. Quite a few twin setups were found on import engines in the 1980s, and quite a few were purchased from Datsun Competition, so they can be found.
ZTherapy is in the USA, and always has them on hand.
Part Numbers
See:
Nissan Competition
Datsun Competition (Nissan Competition) sold a open-vented, non-IMS, system. From the 1984 Nissan Competition catalog.
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GX/SU INDUCTION SYSTEM
The GX/SU induction system was a production line option on non-USA versions of the 1200 and B210. Requires use of GX cylinder head. The GX system can be adapted to virtually any A-series engine.
16010-H2336 38MM SU CARB (FRONT) 16010-H2337 38MM SU CARB (REAR) 14003-H2330 GX INTAKE MANIFOLD 11826-H2300 BLOCK TO MANIFOLD HOSE 14035-H2300 MANIFOLD GASKET 14330-H2303 GX HEAT SHIELD (1) 16031-H2300 OVERFLOW TUBE/FRONT 16031-H2301 OVERFLOW TUBE/REAR 16174-H2300 INSULATOR (2) 16175-A5100 INSULATOR GASKET (2) 16361-H2300 THROTTLE SHAFT ASSY 16376-H2300 ACCELERATOR CABLE BRACKET 17523-H2302 FUEL TUBE (1) 18410-H2302 CHOKE CABLE (1)
Supplied with simple vent tubes (production A12T vents the carburetors to the air cleaner)
With custom-painted black air cleaner & mini heat-shield
PB110
PB110/PB210
46 mm
46 mm (1-7/8 inch bore) twin Hitachis were used on Z-cars and 2000 Roadsters. These are too big for Nissan A engines (even if you use one) and reportedly the late model (1974 260Z) flat-top 46s are not an optimum design.
2-liter U20 engine manifold from Datsun 2000 Roadster (SRL311)
Links
- The Hitachi-SU Tech Pages
- Datsun Service Manual for Hitachi
- buy SU/ZS carbs
- SU tech info from 311s.org
- discussion: NWDE
- http://www.mydatsunroadster.com/2005_07_01_archive.html
- http://www.efn.org/~msayer/zcm/SUTUNE.html
- http://www.ztherapy.com
- http://www.mydatsunroadster.com/2005_08_01_archive.html