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Revision as of 01:54, 4 January 2013

At first glance, all A-series cylinder heads look alike. But by careful notice of specific features you can identify the model.

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.
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.
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:

Head Thickness

Virgin cylinder head thickness is ~74 mm

Buying Used

When inspecting a used head, carry a water bottle. Place the head upside down and fill the combustion chamber with water. If it holds for 5 minutes, the valves are sealing good. Next, check for play on a valve stem. Use a small compressor (I paid $10 for one at a flea market) and see if the valve is tight side-to-side. If it's not, go on to the next head. If it is tight, check a few more (or all of them). Visually inspect for gauges in the head face and manifold faces. Clean-looking heads are best. Pass on slightly rusty heads.

Self-serve wrecking yards have a warranty if you want to do the checking at home.

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

Distinguishing Features

Any A-type cylinder head will bolt onto any A-type engine. However compression and intake ports are big consideration, as are the manifold bolt patterns. For best results, match port types (e.g. round-port manifold on round-port head). The most critical difference is the rocker shaft oil passage. It is in a different place between early and late engines.

Oil passage in the head

An extra oil passage in the head is needed for some engines. For early engines, make sure your head gasket has the hole! You can punch or drill a corresponding hole in the gasket if needed.

Top: 1974, no passage. Bottom: 1973, has passage.

The old 1967-1973 head has the oil passage:

Boss on outside identifies the head

Compare to newer head: no passage:

The newer engine has the passage in the block instead. The solution for Old engine block, Newer head: drill the passage in the head.

Interchanging

Pre-1974 heads fit on all engines.

1974-up block works with any head.

But for newer head on older block, an oil passage must be drilled:

Method 1:

I took off the head, marked it with the old head gasket, and drilled it on a 45 angle. junior

Method 2:

I have seen a crude system where a 1200 head gasket was placed on the head to determine the position of the oil feed hole in the block. This was centerpunched & a very shallow hole was drilled. [about 1 to 1.5mm] then an angle grinder was used to grind a small trench across the gasket face to provide an oil passage froom this shallow hole to the nearest head bolt hole.
Crude as hell, but it worked. A very steady hand would be a prerequisite.
Personally, I would suggest a milling machine if this method is used.
question about oil blockage

Combustion Chamber

All Datsun A-series production heads use a wedge-shaped combustion chamber. However most USA model are open-chambered for lower NOx emissions. The 'heart-shaped' combustion chambers have superior power due to their closed-chamber design with large quench area.

A,B: Heart-shaped high-compression chamber is good for high-octane gasoline
a.k.a: closed chamber, peanut-shaped, butterfly-shaped or kidney-shaped
C: 360 degree open chamber for reduced emissions
D: Bathtub chamber (from 1982 Sunny Truck G61 head)

Any combustion chamber design can fit on any A-series engine.

Comparo - Closed Chamber vs. Open Chamber

Comparo

Chamber Size

A12 closed chamber: 27-29cc
A12T: (M08 head) 32 +/- .5 per 1981 Nissan Racing book
- for 11:1 with GX flattop pistons, GX headgasket,
- mill head 0.9mm (0.035 inch) for 25.6 cc
A12 GX: 29.1 cc (as per FIA papers)
H75: 31cc
H89: 29-31cc
H92: 31cc (A14E head) 29.1 +/- .5 per 1981 Nissan Racing book
H95: 35cc (A15 dish: 6cc)

See CCing Combustion Chamber

Intake Ports

Round: These are best for low-RPM operation

All A12, new A13s, some A14s, and (reportedly) Vanette A15s

Small oval (28 mm x 30 mm). The 1974 A13 has this design.

Small oval with swirl obstruction. These are good for emissions and fuel economy (H95 head, 1981-1982 USA all engines)

Regular oval (28 mm x 34 mm). These std A14/A15 ports are best for high-RPM operation, or for the bigger engines

NOTE: the top of the port comes up to the centerline of the top bolts

Large oval (GX and A12T, 30 mm x 36 mm). From A12GX Engine and B210 or E10 A12T engines.

NOTE: the top of the port comes up as high as the top of the top bolt holes (port comes up past the bolt hole centerline)

GX Oval vs. A14 Oval Comparo

Top: GX ports go much higher than A14/A15 ovals.

Port Sizes

Ports	Size (mm)	Exhaust	Raised	Note
round	28	27x26	no	1971 A12
round	28	?	lowered	1977 GFU
Oval - Small	28x30	?	no	1973 A13
Oval - Medium	28x32	28x26	no	A14E, A15E
Oval - Regular	28x34	28x26	no	Many A14s
Oval - Large (GX)	30x35 - 36	27x29 or 28x26	Yes	A12GX (1971-1973)

GX extra-large oval ports (36 mm tall)

Port Comparison

Wet, Dry Intake Manifolds

Coolant passages are below the intake ports (present or not). If present, they can be large holes or small holes.

See main article: Water Ports

Intake/Exhaust manifold bolt pattern

The 1971-1973 A12 differs from the A13/A14/A15 and some A12s after 1973. A12 Wagons and Trucks continue to use the old pattern for some time

Top: New bolt pattern

Bottom: Original bolt pattern

The bolt pattern on the cylinder heads also differ. early A10/A12 heads are only drilled for the older pattern. Newer A12 (1980s/1990s) are drilled for newer pattern. Some newer heads are drilled for both.

Bolt pattern

Valve Springs

The following A-series heads had dual valve springs. There is a small-diameter spring inside the main spring.

A12GX
early A12T
late A12T
A14T
A14E, A15E
Heads retro-fitted with dual springs

So dual springs are a good indication of a special head, but not conclusive. You will need to check the intake port sizes and other features to make a final determination.

Valves

Valves	Intake PN (13201)	In. Size	Exhaust PN (13202)	Ex. Size	Length
A10, early A12, late A12 Van	13201-H1000	35mm	13202-18000	29mm	103.8
A12GX/A12T	13201-H2300	35mm	13202-H2300	29mm	103.8
Late A12, A13, A12AS	13201-H2300	35mm	13202-H7400	29mm	103.8
A13(1974),A14 & A15	13201-H6200	37mm	13202-H6200, H8900	30mm	103.8
A12A, A14, A15 1981-82 USA	13201-H9500	35mm	13202-H9500	30mm	100.0
A12A, A14, A15 1981-82 canada	13201-H6200	37mm	13202-H6200	30mm	103.8

Nissan Competition

VALVES (A-SERIES)
4 of each required

13201-H2300 35MM/1.38" INTAKE VALVE A12, A12GX
13201-H6200 37MM/1.46" INTAKE VALVE A14, A15
99996-H1100 COMPETITION 37MM/1.46" INTAKE VALVE
13202-H2300 29MM/1.14" EXHAUST VALVE A12, A12GX
13202-H6200 30MM/1.18" EXHAUST VALVE A14, A15
99996-H1110 COMPETITION 30MM/ 1.18" EXHAUST VALVE

Competition Valves are "Polished and 
tuliped for improved flow characteristics".

Reference: 1984 Nissan Competition Catalog

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 original type for left-mount alternator
4-bolt, adds high right-side high alt mount
5-bolt, adds right-side low alt mount
5-bolt with Air Pump air passage

A14T

H72 head

Adapter

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
With boss, drilled

X++

Without boss
- 5-bolt face:
With boss, not drilled, front boss drilled
With boss, drilled, front boss undrilled
With boss, drilled, no front boss

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
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)

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Cylinder Head Identification

Revision as of 01:54, 4 January 2013

Contents

Overview

Head Thickness

Buying Used

Early or Late?

Distinguishing Features

Oil passage in the head

Interchanging

Combustion Chamber

Chamber Size

Intake Ports

Port Sizes

Wet, Dry Intake Manifolds

Intake/Exhaust manifold bolt pattern

Valve Springs

Valves

Nissan Competition

A12GX Head Identification

Port Shape

Exhaust Ports

Intake Ports

Head Front Face

Spark-side Bosses

Manifold-side Bosses

Alternator Mounting

Rear Face

A12GX Identification