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At first glance, all A-series cylinder heads look alike. But by careful notice of specific features you can identify the model.
Contents |
Overview
For the cylinder head, the best way to tell which head you have is to check the casting number in the valve train area (remove the rocker cover to look for this number).
If the head you are looking at does not have a casting number, see the next section: Distinguishing Features.
Once you have the casting number, see Nissan Part Number Prefixes for a table of the different model to part numbers. For example, H23 means the part was originally designed for B110 GX models.
- A10 may have "180", "H01", "257", "H03" or no markings at all
- 1971-1973 A12 may have "180", "H10" or "H39". Some have no markings at all.
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- A12 GX may have "H23" or "230"
- 76 Sunny trucks (A12) may have M30, G25, G61
- 1974 A13 may have "H62" or "620"
- A14 could have several different ones, such as G32, H72 (or 728), H74, H75, H77, H78, H85, H92 or H98 depending upon year, country, and emission control design.
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- M24 or 246 is A14T (Hitachi Twin Carb engine)
- H85 is A12 or A13 (newer engines)
The casting number will be the first 3 digits of the last half of the part number, as all cylinder head part numbers begin with the same 5 digits (11041). For example:
11041-H2300 or 11041-H2301 HEAD ASSY-CYLINDER A12 GX
- 11041 is the base part number for all cylinder heads
- "H23" means the part was first used on the B110 GX vehicle.
- "728" is short for H728x, indicating a B210 "H72" part
references:
- Nissan Part Number Prefixes
- Discussion: Various cylinder heads
- Discussion: A14 head--728-402
Early or Late?
To determine if the head is for an early (pre-1974) or late (1974-up) engine, check for existence of an oil passage here:
Only early engine have the passage in the head here. Of course, one can have the passage drilled on a newer head, but it is a good sign.
To double-check it is an original early head, look at the outside:
Early head: oil passage boss
Late head: no oil passage boss
A12GX Head Identification
One way to identify a GX, when the head is still installed: Look for the oil passage boss (indicating an early head), and for seven studs on the top of the inlet/exhaust manifold gasket. This combination is a good indicator of an GX (or A12T) head. Regular early heads have only five studs along the top of the gasket.
Port Shape
Early head with oval ports is either an A12GX head, or its twin, the early A12T head from the Nissan Cherry (E10). These are the high-revving heads for the factory Hitachi Twin Carb engines.
Exhaust Ports
All heads have nearly square exhaust ports.
Sizes:
- ?
Intake Ports
- Round port 28mm: A12
- Round port 28mm lowered: A14 GFU
- Small Oval port 28x30mm: A13, A12A
- Medium Oval port 28x34mm: A14
- Large Oval port 30x34.5mm: A12GX engine
Head Front Face
- 3-bolt
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- 4-bolt, adds high alt mount
- 4-bolt, adds high alt mount, with air passage
- 5-bolt, adds low alt mount
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A14T 
H72 head
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Spark-side Bosses
Look at the accessory/bracket mounting holes.
No bosses
One boss (undrilled, 1973?):
One boss (drilled, 1973?):
Three boss (late 1970s):
Manifold-side Bosses
- Without boss, early B110
-
- With boss, not drilled, later B110
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- With boss, drilled
-
X++
- Without boss
- 5-bolt face:
- With boss, not drilled, front boss drilled
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- With boss, drilled, front boss undrilled
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- With boss, drilled, no front boss
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Alternator Mounting
Left Side: early A-series engine (front distributor)
- B10,B110,E10: on left side of engine, down low
- Upper bracket bolts to front face of head
-
-
Right Side: late A-series engine (mid-distributor)
- B210, some B310: up high.
- Upper bracket bolts to Upper bolt hole on head
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- Some B310: up low.
- Upper bracket bolts to lower bolt hole on head
-
Rear Face
11041-M0800 early A12T
This head has a factory plug in the heater hose outlet.
One big welch plug
1994 A12S
A12GX Identification
A true A12GX cylinder head has all these features:
- Dual valve springs
- No casting numbers
- Large Oval port 30x34.5mm
- Ports are raised, and extend above upper intake bolts
- 27x29 mm exhaust ports
- closed combustion chamber - heart shaped
- Large size combustion chamber of 29.1 cm3
- large water holes (one under each intake port). Each hole is about the diameter of a pencil (newer heads have small holes)
- Seven upper intake face bolts, nine bolt holes (vs only 5 for other pre-74 heads)
- As with all pre-74 heads, Oil passage on head face (spark plug side)
- Boss on side, between plugs 2 & 3
- SAME valve sizes as standard A12: 29mm exhaust, 35mm intake
- NO bosses on side between plugs 1&2 and 3&4 (that indicates a newer head)