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[Datsun 1200 encyclopedia]

Hitachi Twin Carb

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Categories: Fuel System | Hitachi Twin Carb

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 Union) 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.

Contents

Overview

ヒタチ ツイン キャブレター

13428.jpg 18247.jpg 19100.jpg

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. These are too big for Nissan A engines (even if you use one) and reportedly the late model flat top 46s are a bad design.

Identification

Hitachi Twin Carbs can be broadly broken down by:

  • Dome-tops (B110 and older cars)
  • Flat-tops (B210 and newer cars)
  • Triangular-inlet Choked-carbs (A14.B210 & 260Z)
  • 38mm bore size
  • 46mm bore size (six-cylinder Datsuns)

A12 GX carbs are dome-tops

full-size photo

A12T have flat-top carbs with IMS hoses connecting them
1132.jpg

Nissan Competition carbs are flat-top carbs without IMS

full-size pic

A14T carbs can be identified by the triangular bolt pattern and 38mm bore.
NOTE: 260Z carbs also look like this but are 46mm bore.

full-size photo

Hitachi ID markings are inked (not stamped) onto the float bowl housing.
20159.jpg

Other identifying features include shape of tops, type of fittings, etc.

Flat-Top Hitachi Twin Carbs
th_twin-carb-3.jpg th_twin-carb-1.jpg th_twin-carb-2.jpg th_01.jpg th_02.jpg th_03.jpg th_04.jpg th_05.jpg th_06.jpg th_07.jpg th_08.jpg th_09.jpg th_10.jpg

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.

13415.jpg

  • 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 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.

11041-H2300 HEAD ASSY-CYLINDER A12 GX B110

See main article A12GX Engine

8355.jpg 1973.jpg


Note: A12GX was not fitted with flat-top carburetors.

A12T Engine

See main article: Hitachi Twin Carb A12T

JDM 1973-1975 B210 GX models cam with A12S single-carb engines or the 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".

Flat-tops from A12T.
776.jpg

NOTE: B210 "GX" (Grand Luxury) refers to the car and does not necessarily 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 B120'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.

th_DSC00137.jpg

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).

th_DSC00135.jpg

  • A14T Manifold matches standard A14 gasket

1933.jpg 13406.jpg11824.jpg

  • 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:

  • 18272.jpg


A14T Features:

  • Normal oval-ports (instead of the large GX size)
    18268.jpg
  • A lot of emission controls
  • EGR port on top of manifold
  • Throttle servo
  • Flat-top triangular-bell Hitachis
    13674.jpg
  • 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
    5761.jpg
  • 1.5 inch bore
  • Carb spacing approx 7-1/8 inch
  • Water ports at bottom

SU manifold is different:

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
  • 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 Roadsters: Reportedly, all Roadsters were fitted with Hitachis except the 2000 Roadster (2-liter engine) which came with Solex/Mikuni carbs.
  • Datsun 411 SSS (circa 1966)
  • Datsun 510 (1600) SSS
  • Datsun 610 (180B) SSS
  • Datsun 710 (160J) SSS

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

  1. Nissan Motorsports catalog (#99996-CAT98 and other years)
  2. Nissan Schematic catalog (#99996-M8015)


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

From the 1984 Nissan Competition catalog.

7554.jpg 23782.jpg

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)

7553.jpg

Links

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

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