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The distributor on the Datsun 1200's A12 engine is of the traditional "points" type. Contacts points, rather than an electronic control module, are used to switch the coil on and off thus generating a spark. GX models with the A12GX Engine used a dual-point setup for better spark at high RPMs.
Also see: Ignition Timing
Contents |
Warning
Most old distributors have a bad vacuum advance unit. This goes for wrecking yards, and probably the one in your 1200 too, if you haven't checked it recently. On a recent trip to the wrecking yard, 9 out of 10 circa 1980 Datsun distributors had a bad advance.
See Vacuum Gun
If your advance is bad, plug the vacuum hose until you get a new unit. It will drive fine plugged, but fuel economy will suffer.
Advance Characteristics
For a factory stock USA-specification engine, including 1.5" exhaust, here is the curve. These are for emission-controlled engines.
Centrifugal Advance - part D412-80 for manual transmission
- 0° at 600 rpm
- 12° at 2,100 rpm
Vacuum Advance - part D412-80 for manual transmission
- 0° at 6 inHg (inches of mercury)
- 6.5° at 9.5 inHg
- Mechanical (Centrifugal) advance is all in by 2100 distributor RPM = 4200 crankshaft RPM.
- This is distributor angle. Multiply by two to measure at the crankshaft pulley.
All A-series distributors have similar curves, but vary a little by year and model. Check your Factory Service Manual for your specific model and year to find the curve for your distributor. NOTE: on the side of the distributor is the model number. Mine is D412-63.
The stock design is a nice performance curve. But due to factory tolerances could be several degrees too low for best performance and economy. Blueprint your distributor to ensure it is right.
Total advance is:
5° initial + (13.5 x 2) 27° mechanical = 32° total
Removal & Installation
Interchange
In general you can swap any A-series distributor into any other A-series. Technically, few are a strict interchange do to variations in advance curves used for various years and markets.
When interchanging distributors between 1966-1973 (early A-series) and 1974-2007 (late A-series) engines, minor modification to the mount plate is needed. See Using Newer Distributor.
Part Numbers
All these distributors are physically the same (will bolt right in and connect electrically). The difference is:
- Mechanical advance curve
- Vacuum advance curve
They differ due to differences in requirements for automatic transmission vs manual tranmission, and for emission control requirements.
USA Models
- 22100-H1901 DISTRIBUTOR(HITACHI) EVAPO AT to 1171
- 22100-H1902 DISTRIBUTOR (HITACHI D412-63A) Dec 71-72 AT (Hollander 152)
- 22100-H7100 DISTRIBUTOR 73 AT (Hollander 1060)
- 22100-H3901 DISTRIBUTOR (HITACHI D412-80A) Dec 71-73 MT (Hollander 1059)
- 22100-H1001 ASSY-DISTRIBUTOR(HITACHI) non-EVAPO
- 22136-H2300 ASSY-BRAKER (breaker plate)
- 22136-E4600 ASSY-BRAKER PLATE from 1271
- 22145-18005 SET-CONTACT
- 22157-H1000 ROTOR-HEAD, formerly 22157-78500
- 22162-21007 CAP
- 22165-30101 POINT-CARBON
- 22102-00801 CONDENSOR
- 22100-25720 (no vacuum advance)
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Vacuum Advance
ASS'Y-VACUUM CONTROL
- 22301-H1000 non-EVAPO superseded by part number 22301-M1500 $27.25
- 22301-B3000 EVAPO
- 22301-B3001 EVAPO (formerly 22301-B3000) $35.07
- 22301-H3900 EVAPO from 0671 $35.92
- 22301-H3901 EVAPO from 1271 (formerly 22301-H3900) $32.22
- 22301-H1900 EVAPO AUTO from 1271 (formerly 22301-B0300) $30.13
- 22301-E4603 EVAPO AUTO from 0772 (formerly 22301-H1900) $39.13
Orange:
- 4mm travel adjustment
- Inside needle height: 21.5 mm (from spring seat)
- Spring 33.5 mm free height
- Diaphragm diameter approx 52mm
The needle/screw height adjust max travel. The spring sets the starting point.
- diameter: 63 mm (cut gasket larger)
Possible Fit:
Electronic Distributor Upgrades
For converting your A12 to electronic ignition, see: