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[Datsun 1200 encyclopedia]

A-series Cylinder Heads

From Datsun 1200 Club

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Categories: Engine Mechanical | Cylinder Heads

Nissan A-series Engine cylinder heads are of one type: inline valves, pushrod valve system (non-overhead cam), two-valves per cylinder. The head is non-crossflow meaning that exhaust and intake ports are on the same side (left side). An exception to the above is the work AY12 head. It is cast in aluminum and unlike the BMC A-series bathtub chamber design, the Datsun A-series uses a more modern wedge-shaped chamber with inclined valves.

Contents

Application

For application by Datsun model, see Cylinder Head Part Numbers.

Cylinder Head Identification

Most A-engine heads do not have unique casting numbers. For a process of identification see Cylinder Head Identification. The article also discusses various distinguishing features of the various cylinder heads and includes many photos.

Early A Engine

The 1967-1973 heads provide oil to the rocker arm shafts in different locations than 1974-up, so when fitting a newer head you may need to redrill the oil passage.

Round Port

All early (pre-1974) A-series round-port engines uses the following
* 35 mm Intake valves 13201-H1000 
* 29 mm Exhaust valves 13202-18000 
* Dry type manifold 
* 14035-18000 GASKET-manifold to head
* Original manifold bolt pattern

A10 head

The 1970 B10 is 9.0:1, same as the B110 ratio. Yet they use the exact same head. This indicates the B10 piston dish is 20% larger.

* (optional) Rally Springs (dual valve springs) 
* Early heads have non-A12 fittings
* Late A10 heads are same as A12

B10 Coupe Head

B10 Coupe with A10 engine had different part number. It is unknown how it differs from the regular Datsun 1000 cylinder head.

It is fitted with flattops pistons (same as the Hi-Gas A12GX pistons), and a dual-outlet exhaust manifold.

A10 M01 Head

11041-M0100 HEAD ASSY-cylinder E10 JDM
11041-M0101 HEAD ASSY-cylinder E10 JDM (from '72-1)
11041-M0102 HEAD ASSY-CYLINDER E10 JDM
11041-M0105 HEAD ASSY-CYLINDER N10 EUR 0878-0781 
11041-M0104 HEAD ASSY-CYLINDER N10 EUR 0878-0781

A12 H10 Head

H10 head has no casting numbers
* JDM B110
* USA B110 Early 1971 model (until April 1971) 
* Closed Chamber

15690.jpgAlbum click to view

Known in SCCA racing circles as the "H Production" head, legal alternative for H39 head.

See discussion: Are these A series GX or comp heads? Experts needed!

Some say a ported and polished standard A12 head with larger valves fitted flows about the same as a standard GX head. See head trivia.

A12 H15 Head

From Nissan Cherry E10

A12 H39 Head

* USA B110, from April 1971
head has no casting numbers
* Same as H10 head, but with open chambers
* Compression ratio 9.0:1 with dished pistons

Open Chamber heads are most common in USA. They were fitted mid-1971 to remove the temperature-spiking "quench" area thereby reducing NOx (nitrogen oxides) emissions.

4587.jpgAlbum click to view 4588.jpgAlbum click to view

Large Oval Port

All Large Oval-port engines use the following:
* 35 mm Intake valves 13201-H2300 
* 29 mm Exhaust valves 13202-H2300 
* Wet type manifold 
* 14035-H2300 GASKET-manifold to head
* Original manifold bolt pattern

A12GX Head

Cast "JAPAN" and "NISSAN"
* Large Oval Ports (30 x 36 mm)
* Same size valves as A10 & A12 engine
  22116.jpgAlbum click to view

The A12GX Engine uses a cylinder head with dual-valve springs for 6800 rpm operation
(compare to stock A12 6400 rpm operation). It used an intake manifold with dual Hitachi HJE38W side-draft carburetors. Compression ratio of 10.0 and combustion chamber of 29.1 cm3 with flat-top pistons.

Dual valve springs, GX cylinder head and intake
504.jpgAlbum click to view 1002.jpgAlbum click to view

  • 11041-H2302 A12 GX cylinder head (to 6/73)
  • 11041-H5703 GX cylinder head (from 7/73) same specs, but for newer engine style


NOTE: Dual valve springs alone is not an indication of the GX head. N10 A14E engines also used dual-springs, but were not large-port heads. Also over the years many heads have had dual springs added. For ID, check the intake port sizes.

For more details, see Main Article: A12GX Engine

head1-1.jpg head1-2.jpg head1-3.jpg

Early A12T Head

Cherry E10 model has a head same or very similar to the A12GX head (11041-H2300):

 11041-M0800

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Late A Engine

1974-up A Engine Redesign heads provide oil to the rocker armshafts in different locations than earlier heads. The new heads do not have the oil passage on their face, so when swapping into earlier blocks you need to drill the oil passage.

Round Port

Round ports heads were used by all A12s & some A14/A15.

  • Some A12s use the original bolt pattern while other A12s have the new-type bolt pattern
  • Valve sizes vary

728

A14 Round Port head, high swirl type, for the FU Engine 1977-1979.

11041-H7281, 11041-H7282, 11041-H7283
Round Port, Large Valves
Dry manifold
Closed chambers
Intake: 37mm
Exhaust: 30mm
14035-H7400 GASKET-MANIFOLD TO CYLINDER HEAD

728-402
13913.jpgAlbum click to view 13914.jpgAlbum click to view

Lowered-port high-swirl design for the FU Engine. 728 heads were also used on 1978-1982 Canada models (B210 & B310).

9058.jpgAlbum click to view 23745.jpgAlbum click to view

These have quench chambers (closed chambers) but instead of being used in high-compression engines, they are designed for high swirl (for better fuel economy and improved emissions). They are used with dished pistons for 8.5:1 in 1977 and 9.0:1 in 1978 FU (4mm dish or 5mm dish). Unlike the swirl-port heads, these have unobstructed ports. The ports are lowered so that the charge is forced to swirl as it enters the chamber.

23744.jpgAlbum click to view

G22

Casting mark unknown. Nissan part number G2201

11041-G2201
11041-G2201.jpg 11041-G2201_.jpg 11041-G2201-.jpg 11041-G2201-1.jpg

G25

A12 G25 head used by B120.

Both bolt patterns, Dry manifold (G16 also has both patterns, but uses wet type manifold)

11041-G2560 HEAD ASSY-CYLINDER 7908-8109 <> 11041-G2561
11041-G2561 HEAD ASSY-CYLINDER 8110-8910
* G25 cast number
* Dry manifold (G16 is wet)
* Closed Chamber  
* Both bolt patterns (like G16 8910-)
* Longer next-to-last top stud compared to G16
* 2 or 3 bosses? on face with 2-bolt Thermostat Housing
* Intake valve: H10/H23
* Exhaust valve: 180/H74
58 hp
* uses 25080-H89900 through Jan 1982, then 25080-89912 from Feb 1982
  early
  th_25080-89900.jpg
  late
  25080-89912.jpg

h1.jpg h2.jpg h3.jpg h4.jpg 15727.jpgAlbum click to view 15726.jpgAlbum click to view 1233.jpgAlbum click to view

G32

11041-G3202 HEAD ASSY-CYLINDER A14S.V JDM A10 7907-
* 14035-H7400 GASKET-MANIFOLD TO CYLINDER HEAD A14S.V 7906-
* Round Port A14
* Intake valve: 37mm 13201-H6200
* Exhaust valve: 30mm 13202-H6200
  replaced by 13202-H8900 7907-
* 14035-H7201 GASKET-MANIFOLD to CYLINDER HEAD

G61

A12 G61 head.

11041-G6100 HEAD ASSY-CYLINDER B120 8910-
Wet manifold 
Closed Chamber, deep shroud
Both bolt patterns (like 11041-G2560/11041-G2561 7908-8910)
Shorter next-to-last top stud compared to G25
3 bosses on face with 2-bolt Thermostat Housing
Intake valve: H23
Exhaust valve: H74
58 hp
* uses 25080-89912 exclusively 
  25080-89912.jpg

16014.jpgAlbum click to view 16015.jpgAlbum click to view 16430.jpgAlbum click to view 16431.jpgAlbum click to view 16432.jpgAlbum click to view

H50

The new-style A12 head (without oil passage on face of head).

11041-H5002 B210 A12 -7509

H81

Sweden emissions head.

* Intake valves: 35mm 13201-H1000
* Exhaust valves: 29mm 13202-H1000
Gasket 14035-18000
* Dry type
* Original bolt pattern
* round ports

H74

H74 Head was fitted to late JDM B210 Van (from October 1975)
* Intake valves: 35mm 13201-H2300
* Exhaust valves: 29mm 13202-H7400
* Round Port
* Dry Intake
* New intake bolt pattern
* 14035-H7400 Gasket-head to manifold
11041-H7401 HEAD ASSY-CYLINDER A12S S,K -7612
11041-H7403 HEAD ASSY-CYLINDER A12S S,K 7701-

H78

A14 H78 Round Port Head

A14: (H78) Round Port, dry manifold, large valve A14S Van
* 14035-H7400 GASKET-MANIFOLD TO CYLINDER HEAD
11041-H7863 HEAD ASSY-CYLINDER A14S V A10 7807-7906

H85

A12A, A13 cylinder head

* Intake valves: 35mm 13201-H2300
* Exhaust valves: 13202-H7400
* Round Port
* Intake Water Ports
* New intake bolt pattern
* 11035-H8501 GASKET-MANIFOLD TO CYLINDER HEAD A12S.S,K
11041-H8500 HEAD ASSY-CYLINDER A12S.S,K B310 JDM N-7909 11041-H8501
11041-H8501 HEAD ASSY-CYLINDER S,K.A12S B310 JDM 7910-8010 
* 14035-H8660 GASKET-MANIFOLD TO CYLINDER HEAD A13S, A15 JDM 8011-
11041-H8503 HEAD ASSY-CYLINDER A13S 8011-

tmatpit103-img600x450-12358090555nlzem31964.jpg tmatpit103-img600x450-12358090561dtnhk31964.jpg tmatpit103-img600x450-12358090562y4nwi31964.jpg


H990

For 1980, wet intake replaced dry intake. USA FED A12/A14/A15 round port, wet intake, new bolt pattern.

Has round intake ports (like the A12 head). Casting numbers are under the valve cover area: "990" towards the rear and "454" towards the front. These cannot be ported out to match the oval port heads (you'll hit a water jacket). It has two small coolant holes below the intake ports, to provide heat for the intake manifold. These came on the "FU" and "MPG" cars (USA-market B310 fuel economy champion models).

Has "990" cast near #4 cylinder and "415" at the #1 end
18153.jpgAlbum click to view

H991

USA A12A 
CAL A14/A15

H916

CAL A14/A15

M30

A12 M30 head Low-po Van/Truck engine. Also used in Europe cars except Sweden emissions.

* 14035-18000 Manifold gasket
* 11041-M3000 -7803
  B120 Sunny Truck 7510-7907
* 11041-M3001 7804-7907
  B210 JDM Late A12 Van
  B310 JDM A12S Van -7909
  F10 JDM A12S Van
  N10 JDM A12S Van
  EUR N10 A12S except SWE
* Intake valves: 35mm 13201-H1000
* Exhaust valves: 29mm 13202-18000
* Dry manifold
* Closed Chamber
* Cast "M30" 
* Original bolt pattern

21405.jpgAlbum click to view 21406.jpgAlbum click to view 21407.jpgAlbum click to view

M30-060
21408.jpgAlbum click to view 21409.jpgAlbum click to view

M30-064
12726.jpgAlbum click to view

Small Oval Port

A13 H62 Head

The 1974 A13 engine for North America featured small 28 x 30 mm oval ports.

H62 more info
* Open chambers
* Small Oval Port (28 x 30 mm)
  14035-H6200 GASKET-MANIFOLD TO CYLINDER HEAD
* Dry manifold
* Large Valves (A14 size)
* New bolt pattern (also drilled/tapped for old bolt pattern)
USA B210 1974
11041-H6200 ASSY-HEAD CYLINDER A13
11041-H6201 ASSY-HEAD CYLINDER A13
11041-H6202 ASSY-HEAD CYLINDER A13

26747.jpgAlbum click to view 26748.jpgAlbum click to view 26749.jpgAlbum click to view

H95 Small-Oval Shrouded-port Head

Also see: H95 Engine

* Used on all USA engines 1981-1982 (A12A, A14 and A15)
* Intake: 37mm, 100.0 mm
* Exhaust: 30mm, , 100.0 mm
NOTE: All other A-series valves are 103.8 mm long
* peanut-shaped combustion chambers
* Small-oval ports, guide is shrouded
* wet intake
* 14035-H8901 manifold gasket (same as Large Size ports)

Has an H95 cast into it, under the valve cover area, has what some call a "swirl" port has an obstruction cast into the port to cause the flow to swirl but it reduces total flow. If you look into the port, from the manifold side, you'll see a heavily shrouded port, almost half of the size it would normally be on an A14 head.

4444.jpgAlbum click to view

If you try to grind out this obstruction, you will hit a water jacket and render the head useless. It too, has the coolant holes in it.

They also have a small but deep combustion chamber, hence a different dish in the piston.

15779.jpgAlbum click to view 11041-H9500-.jpg 11041-H9500.jpg 11041-H9500_.jpg

Regular Oval Port

The A14/A15 Oval-port Heads include large 37 mm intake valves and 30 mm exhaust valves.
  • There are many part numbers, which differ for year, emission control, accessory fittings, coolant passages, etc.
  • These heads first appeared with the 1975 A14 engine.
  • Open Chamber versions can can be milled .080" or more to raise compression.


Oval-Port heads include:

  • H72: Dry, Large Oval, Open Chamber. The original A14 head, designed for USA market. With Air Pump passage
  • H77: Same as H72 but drilled for more emission controls
  • H75: Same as H72 but for non-USA market w/o Air Pump
  • H89: Closed Chamber Wet manifold use in B310
  • M24: For twin-carb A14T, similar to H89 but with dual-valve springs

G51

Late model Vanette large-bore head (A14/A15)

14035-H8901 Gasket-manifold to head
* Wet Type 
* 14035-05H01
* Intake valves: 37mm 13201-H6200
* Exhaust valves: 30mm 13202-H6200 
11041-G5100 HEAD ASSY-CYLINDER GC22 EUR.LHD A15 0986-1190
11041-G5100 HEAD ASSY-CYLINDER C22 JDM
11041-G5101 HEAD ASSY-CYLINDER C22 JDM
11041-G5200 HEAD ASSY-CYLINDER GC22 EUR.LHD A15 1190-

H72

The original A14 head. Designed for north america, it has open combustion chambers and is drilled for AIS air injection passages.

B210 USA '75-0777
* Cast "H72" and "108"
* Cast "H72" and "104" is #H77
* Open chamber
* Dry Type
* Oval Ports
* Air-exhaust passage
14035-H7200 Gasket-manifold to head

5254.jpgAlbum click to view

Sometimes erroneously called the "low compression GX head", it has a casting number "H72". Has a larger 360-degree "open" combustion chamber for reduced emissions. It does not have the coolant holes below the intake ports, so uses a 'dry' type inlet manifold. It has the nice straight big oval intake ports. It is better than the A14 oval "swirl port" (H95) head, and certainly better for high RPM use than the round intake port A14 heads. Air pump galley drilled from front face all the way back through, intersecting all the exhaust ports.

Open Chamber design
5250.jpgAlbum click to view

So is Oval-port "H72" a good head or not? [Naukkis] says the "high-compression" (closed chamber) head is a better design, and not just because of the compression (see POST New A series oval port head). The quench design of the combustion chamber is more efficient. The best combo for low compression would undoubtedly be a high-compression head used with half-dished pistons (half-flat-top, half dish), but are these available for the A-type engines?

19874.jpgAlbum click to view 19875.jpgAlbum click to view 13804.jpgAlbum click to view

Note AIS air passage for Thermostat_Housing#4-bolt_Type
22082.jpgAlbum click to view 25820.jpgAlbum click to view

22084.jpgAlbum click to view

Note the "extra water port" at the rear, plugged in 1975, but fitted with a sensor/switch in others:
22085.jpgAlbum click to view

The original A14 head (H72) has the oil boss casting like early A12 heads, only it is not drilled & plugged:
22086.jpgAlbum click to view

H75

A14: marked 'H75' and '309'
* H75
* #H78_2 (machined chamber)
11041-H7500 HEAD ASSY-CYLINDER JDM Late B210 A14S Van
11041-H7502 HEAD ASSY-CYLINDER F10 JDM A14S
11041-H7502 HEAD ASSY-CYLINDER A10 JDM A14S.S,K -7803
* 14035-H7200 GASKET-MANIFOLD TO CYLINDER HEAD
* Intake valves: 37mm 13201-H6200 
* Exhaust valves: 30mm 13202-H6200 
* Oval Ports 
* Dry Intake
* Open Chamber design, 31cc

H78
6290.jpgAlbum click to view 6291.jpgAlbum click to view 6292.jpgAlbum click to view 7952_4c03634ca8e3d.jpgPost click for topic 7952_4c03632216a8a.jpgPost click for topic 7952_4c036332be99a.jpgPost click for topic 7952_4c03633bc135a.jpgPost click for topic 7952_4c03635892a13.jpgPost click for topic

Polished
21769.jpgAlbum click to view 21771.jpgAlbum click to view 21770.jpgAlbum click to view

H77

Same as H72 but with different emission provision
* Cast "H72" and "104"
* rear port face boss (for water sensor) is undrilled
* B210 USA A14S 0877- non-5speed models
* B310 USA FED 1980 model year
* N10 USA A14S Federal 0878-0779
* Open chamber
* Dry Type
* Oval Ports
* Air-exhaust passage
14035-H7200 Gasket-manifold to head

22080.jpgAlbum click to view 22081.jpgAlbum click to view 22082.jpgAlbum click to view

H78

A14 H78 Oval Port Head

  • Uses #H75 casting
  • Also see #H78 round-port head
A14: (H78) Oval Port, dry manifold, large valve A14S Van
* 14035-H7860 GASKET-MANIFOLD TO CYLINDER HEAD
11041-H7860 HEAD ASSY-CYLINDER A14S V B210
11041-H7861 HEAD ASSY-CYLINDER A14S V A10 -7806

H89

Oval-port Closed-Chamber was fitted to A14-powered B310 Coupe and Sedan in the JDM market. C120 came with A15 engine and H89 head. Closed-chamber is a non-emissions controlled head (no EGR). It is sometimes called "High Compression", but the chambers are about the same size as the open chamber (H72) head -- the compression is controlled by the piston dish, not the head.

* Closed Chamber
* Oval Port 
* Intake Water Ports 
* New intake bolt pattern

Small water holes beneath intake ports
14886.jpgAlbum click to view
174_5cdbb23c4a79f.jpgPost click for topic

Vanette A15 version with dual bolt-pattern
12967.jpgAlbum click to view

Standard large valve set (35mm intake/30mm exhaust)
7629.jpgAlbum click to view

5-bolt front face
H892.jpg 174_5cdbb01c8680b.jpgPost click for topic

'H89' primary casting ID (front of head) reads 98H upside-down
174_5cdbad0e3023a.jpgPost click for topic

various secondary casting ID (rear of head) including '610' 'G51' '801'
174_5cdbad160c3ec.jpgPost click for topic

Closed combustion chambers
174_5cdbab58e0dad.jpgPost click for topic 174_5cdbab3523af8.jpgPost click for topic 174_5cdbab4fc73a0.jpgPost click for topic

1234.jpgAlbum click to view 15189.jpgAlbum click to view 16021.jpgAlbum click to view

Secondary 908/809 ID mark
Photo0724_zps5d384311.jpg Photo0725_zpsbae7c1cd.jpg Photo0728_zps61907b06.jpg Photo0716_zpsa4433d3d.jpg

'H891' and 'G15' cast marks
G15a.jpg G15b.jpg G15c.jpg

H99

* USA N10 A14S 0879-0780
* Similar to FU Engine and late model G61 A12
* Round Port for A14
* Closed chamber
* Wet type

22075.jpgAlbum click to view 22076.jpgAlbum click to view 22077.jpgAlbum click to view 22078.jpgAlbum click to view 22079.jpgAlbum click to view

11041-H9902-1.jpg 11041-H9902-2.jpg 11041-H9902-3.jpg

M24

M24 Head from A14T engine
* Intake valves: 37mm 13201-H6200
* Exhaust valves: 30mm 13202-H6200
* Dual valve springs
* Oval Ports (smaller than GX, same size as standard A14)
** Intake-to-Head gasket 14035-H7200
11041-M2460 HEAD ASSY-CYLINDER A14T B210 JDM

M66

A15S new type combustion 
* USA N10 (Pulsar) "Datsun 210" 0880-0781
* Wet type
* Oval Port
* INTAKE 35mm: 13201-H9500
* EXHAUST 30mm: 13202-H9500
* 14035-H8901 Gasket-manifold to head
** interchangeable with 14035-05H01
11041-M6600 HEAD ASSY-CYLINDER

M49

EFI Oval Port

Unknown size intake ports in the cylinder heads used by A14E and A15E EFI, but 28x32 intake manifold ports.

H92

The EGI heads. Fitted to A14E and A15E in Asia-market B310s and N10s.

N10 JDM A14E
 11041-H9200 -7908
 11041-H9202 7909-8004
 11041-H9204 8005-8102 [8103- used E15 engine]
B310 JDM A14E
 11041-H9200 -7810
 11041-H9201 7811-7903
 11041-H9202 7904-7907
 11041-H9204 7908-8010
A15E B310 JDM
 11041-H9204 8011- [same as A14E]
* Intake valves: 37mm 13201-H6200
* Exhaust valves: 30mm 13202-H6200 replaced by 13202-H8900 7910-
* Dual valve springs
14035-H9201 Manifold gasket
* Wet manifold
* Oval Ports with ?notch for injector
* Intake: 28x32 mm oval with injection cutout of extending up to 40mm 
* compare to standard A14: 28x34 
  22088.jpgAlbum click to view

EGI Intake Manifold Comparo
21834.jpgAlbum click to view

Compared to regular gasket:
21848.jpgAlbum click to view

Large Oval Port

H57

Late A12T from B210 Sunny and E10 Cherry. Appears to be the same as the #Early A12T Head, except the head has no oil passage on the face of the head.

Nissan Competition Catalog

From 1984 Nissan Competition Catalog

th_Competition198438.jpg
* 11041-H2302 GX CYLINDER CYLINDER HEAD (TO 6/73)
* 11041-H5703 GX CYLINDER HEAD (FROM 7/73)
* 99996-H1167 COMPETITION CYLINDER HEAD (TO 6/73)
* 99996-H1165 COMPETITION CYLINDER HEAD (FROM 7/73)

CYLINDER HEADS & COMPONENTS (A-SERIES)

  • 11041-H2302 GX CYLINDER HEAD (TO 6/73) For use with any A-series engine built up to 6/73. It has a 29cc combustion chamber and, due to its large intake port size, must be used with either the GX or Mikuni/Solex intake manifold. Valve size is 35mm/1.38" (intake) and 29mm/1.14" (exhaust)
  • 11041-H5703 GX CYLINDER HEAD (FROM 7/73) Specifications are the same as 11041-H2302. For A-series engines built from 7/73
  • 99996-H1167 COMPETITION CYLINDER HEAD (TO 6/73) This cylinder head is recommended for racing purposes only. Must be used with either the GX or Mikuni/Solex intake manifold. Completely ported, polished and fitted with competition intake (37mm/1.46") and exhaust (30mm/1.18") valves. For A-series engines built up to 6/73
  • 99996-H1165 COMPETITION CYLINDER HEAD (FROM 7/73) Specifications are the same as 99996-H1167. For A-series engines built from 7/73
  • 11056-H2301 GX HEAD BOLT Torque spec = 58 ft/lbs (9 needed)
  • 11057-H2301 GX HEAD BOLT (TO 6/73) Torque spec = 58 ft/lbs (1 needed)
  • 11057-H5700 GX HEAD BOLT (FROM 7/73) Torque spec = 58 ft/lbs (1 needed)
  • 14035-M0821 COMPETITION HEAD GASKET Gasket has a bore diameter of 79mm/3.11", an uncrushed thickness of 0.8mm/ 0.032" and displaces 3.9cc's

Competition Head

99996-H1165 pictured
22117.jpg
* Intake: 35mm (optional 37mm)
* Exhaust: 29mm (optional 30mm)

This cylinder head is recommended for racing purposes only. Must be used with either the GX or Mikuni/Solex intake manifold. Completely ported, polished and fitted with competition intake (37mm/1.46") and exhaust (30mm/1.18") valves.

The Competition Head has the large oval ports and a small heart-shaped chamber (Closed Chamber) and was available from Datsun Competition, later called Nissan Competition and then Nismo. The part is unforunately now NLA (No Longer Available). This race cylinder head reported has the same 29 cc chamber volume as the A12GX head.

Sometimes the Competition Head is erroneously called the A14 "GX" head because it is similar to the GX casting but fitted with the A14 size valves.

  • 99996-H1167 Competition Cylinder Head (to 6/73)
  • 99996-H1165 Competition Cylinder Head (from 6/74)

Presumably the difference in the two Competition Head part numbers only differ in the oil passage and fittings/bolt holes.

The Competition heads are "recommended for racing purposes only ... ported, polished ... competition intake (37 mm)... competition exhaust (30 mm)" -- in other words, the same valve sizes as regular A14 heads. However, the valves are tulip-machined for better flow.

99996-H1165
th_99996-H1165a.jpg th_99996-H1165b.jpg th_99996-H1165c.jpg th_99996-H1165d.jpg th_99996-H1165e.jpg th_99996-H1165f.jpg th_99996-H1165g.jpg th_99996-H1165h.jpg th_99996-H1165i.jpg

99996-H1131 retainers
full

Other heads

Anyone have more information on these?

  • There is apparently an A14 Oval Port "GX" head which flows more than the A12GX head. reference: GX Head or A15
  • An A15 "GX" head was used by Nissan for racing. There are several different chamber shapes and sizes but just the improved flow though the oval ports is better than the stock round ones. The valve sizes should be larger and some were fitted with dual valve springs.

High Roof Heads

  • High-port heads. Are these the Competition Heads? Or some other kind of racing-only head?
    1245.gif
    4413.jpg

18946.jpg 18947.jpg

Also see: Cylinder Head Modifications Raised-Ports.

Part Numbers

See Cylinder Head Part Numbers

DOHC Heads for A-series

See DOHC Heads

AY12 Racing Head

There was one exception: The race-only AY12 cylinder head:
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