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Revision as of 05:32, 26 December 2008

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.

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.

1 Three Different Designs
2 Retro-fitting
3 Variations
4 Parts Donors
5 Damper Oil
6 Tuning
7 Troubleshooting
8 References
9 Parts Suppliers
10 Links
11 Photo Index

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 GX Engine

Also see: A12GX Part Numbers

 See main article A12GX Engine

The Datsun 1200 GX (Grand Luxe Twin-carb) models were fitted with the A12 GX Engine. This 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.

A12T Engine

JDM 1974-1975 B210 GX models had the A12T twin-carb engine (also known as GX-T). While very similar to the A12 GX Engine, the A12T engine used different flattop Hitachis and a slightly different intake manifold with a few more fittings. Reportedly, these are decent carburetors that only need a few simple modifications.

11041-H5702 HEAD ASS'Y-cylinder A12T

NOTE: B210 "GX" refers to the car only and does not necessarily mean the car included a twin-carb engine as the B110 GX did. While Japan-market B210 GX did include the A12T engine, however outside Japan most B210 GX models were fitted with a single-carb (A12S) engine.

JDM Datsun Cherry (E10) models also used the A12T engine, especially notable was the Cherry X1-R vehicle.

11041-M0801 HEAD ASSY-CYLINDER A12T

This head looks like the A12GX head. Most likely the fittings and accessory bolts are slightly different from the A12GX version.

A14T Engine

Starting around 1976, the B120's A12T was phased out and the A14T started. 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 used a single tube exhaust manifold (A12 twin-carb engines used twin-outlet exhaust manifold).

11041-M2460 HEAD ASSY-CYLINDER A14T

Datsun Cherry (F10) models with A14T engine also used the very same cylinder head.

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 (see: A14T Part Numbers.

A14T engines use flat-top carbs, probably the same as L18SSS engines, heavily modified from the A12 type Hitachis, apparently to manage emission control.

LOOK! A14T manifold photo gallery
*

A14T Features:

EGR port
Flat-top triangular-bell Hitachis
Vacuum ports on each end, top of manifold
No PCV valve fitting

Carb side:

4-bolt pattern on 3.5 in. circle
1.5 inch bore
Carb spacing approx 7-1/8 inch
Water ports at bottom

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

Dome Tops vs Flat tops:

Dome Tops are early models
Flat Tops are 1974-up with emission controls

38 mm

HJB38W: Roadster R engine (SPL311-1600)
HJB38W-3: Roadster with G engine, also 1968 R engine)
HJE38W: B110
HJL38W6: 510 L16 & L18

46 mm

HJG46W: Roadster U20 (SRL311-2000)

Parts Donors

A12 GX import engines
Datsun Competition setups
Datsun Roadsters: Reportedly, all Roadsters were fitted with Hitachis except the 2000 Roadster (2-liter engine) which came with Solex carbs.
Datsun 411 SSS (circa 1966)
Datsun 510 SSS
Datsun 610/710 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

Go here for lots of information: The Hitachi-SU Tech Pages.

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)

Parts Suppliers

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.