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Revision as of 05:22, 7 June 2010

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).

1 Cylinder Head Identification
2 Head Types
3 Distinguishing Features
4 Early A Engine
- 4.1 Round Port
- 4.2 Large Oval Port
  - 4.2.1 A12GX Head
  - 4.2.2 Early A12T Head
5 Late A Engine
6 Competition Head
7 Other heads
8 High Roof Heads
9 Measuring Combustion Chamber Volume
10 Which Cylinder Head is "Best"?
- 10.1 So which is better for a street engine?
11 Modifying a Head
12 Part Numbers
13 DOHC Heads for A-series
14 AY12 Racing Head

Cylinder Head Identification

Most A-engine heads do not have unique casting numbers. For a process of identification see Cylinder Head Identification. This article will discuss various features of cylinder head.

Head Types

Early

A10: (180/H01) Round port, dry manifold, early B10 fittings
KB10: (257/H03) larger chamber size???
A12: (H10) Round Port, late A10, A12, A12S Van, Early Truck
A12: (H39) Round Port, Open Chamber USA B110
GX: (H23) Extra-large Oval Port, wet manifold A12GX
A12T: (M08) Same as GX, but for Datsun Cherry

Late - for A Engine Redesign

A12S: (H50/H30) new Round Port, dry manifold A12S Van, Late Truck
A12T: (H57) Extra Large oval with new oiling passage
A12S: (H74) new Round Port, dry manifold A12S Van, new pattern
A12S: (H85) new Round Port, wet manifold A12S, A13S
G25: A12S 7910-, B120, B310 Van
G32: A14S 7910- van
G61: Late A12 8910-
H62: A13 (1974), Medium Oval Port, A14-type large valves
A14T: (M24) regular oval with dual springs
A14: (H75) Round Port, dry manifold, large valve A14S Van
A14: (H78) new Round Port, wet manifold, large valve A14S Van, FU Engine
A14: (M49, H77) Oval Port, dry manifold, A14
H85: A12S 7910- round, wet, new except Van
H89: Oval Port, wet manifold A14S, A15S, A14T
H92: Medium Oval, wet manifold A14E, A15E
H95: swirl port oval (A12A, A14, A15) 1981-1982 USA

"New" means the updated intake manifold bolt pattern (see Bolt Pattern section below).

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

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 swirl port head)?

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

Comparo - Closed Chamber vs. Open Chamber

Comparo

Chamber Size

A12:
A12 GX: 29.1 cc (as per FIA papers)

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
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

Intake Manifolds

All A-series heads will interchange with either type of intake with the following caveats:

If the intake doesn't have coolant passages, tap the head's coolant ports and install plugs
<li>If the intake does, but the head doesn't, cold-weather starting and cold-idle may suffer due to insufficient heat. However, warm-engine operation should be OK.

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.

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
A12T
A14T
A14E
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.

Valve sizes

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

Coolant Passages

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

A12GX has Four Large coolant holes, one beneath each inlet

Other heads have either no coolant holes, small ones, or a mix:

Standard Datsun 1200 heads have no coolant holes on the intake side.

Early A Engine

The 1967-1973 heads provide oil to the rocker armshafts in different locations than 1974-up, so when swapping 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

A12 H10 Head

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

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 therefore reducing NOx (nitrogen oxides) emissions.

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

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

11041-H2302 A12 GX cylinder head (to 6/73)
11041-H5703 GX cylinder head (from 7/73) same specs, but for newer engine style
- Nissan Competition called the newer head a "GX" head. But this appears to be the A12T head (11041-H5702).

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

Early A12T Head

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

 11041-M0800

Late A Engine

1974-up A Engine Redesign

Round Port

Round ports heads were used by all A12s & some A14s.

Comparision: bolt pattern
Top: New bolt pattern

Bottom: Original bolt pattern

H74

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

A12 M30 Head

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

11041-M3000 HEAD ASSY-CYLINDER B210 Van -7612, B120 7510-7803
Dry manifold
Lowered ports
Closed Chamber
Original bolt pattern

A12 G25 Head

* 11041-G2560 HEAD ASSY-CYLINDER 7908-8109
* 11041-G2561 HEAD ASSY-CYLINDER 8110-8910
G25 cast number
Dry manifold 
Closed Chamber 
New bolt pattern

G32

* Round Port A14
* Intake valve: 37mm 13201-H6200
* Exhaust valve: 30mm 13202-H6200, replaced by 13202-H8900 7907-
* 11044-H7201 GASKET-CYLINDER HEAD
* 14035-H7400 GASKET-MANIFOLD TO CYLINDER HEAD A14S.V 7906-
11041-G3202 HEAD ASSY-CYLINDER A14S.V JDM A10 7907-

A12 G61 Head

11041-G6100 HEAD ASSY-CYLINDER B120 8910-
Wet manifold 
Closed Chamber 
New bolt pattern

A14 FU Round Port head

For the FU Engine 1976-1977
Intake: 37mm
Exhaust: 30mm

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 "GFU" and "MPG" cars (USA-market B210 and B310 fuel economy champion models).

Has "990" cast near #4 cylinder and "415" at the #1 end

A14 FU High-Swirl head

1977 & 1978 lowered-port high-swirl design for the FU Engine.

These have quench chambers (not open 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. 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.

H85

* 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

* 11044-H8660 GASKET-MANIFOLD TO CYLINDER HEAD A13S, A15 JDM 8011-
11041-H8503 HEAD ASSY-CYLINDER A13S 8011-

A14 H78 Round Port Head

A14: (H78) Round Port, dry manifold, large valve A14S Van
* 11044-H7400 GASKET-MANIFOLD TO CYLINDER HEAD
11041-H7863 HEAD ASSY-CYLINDER A14S V A10 7807-7906

Small Oval Port

A13 H62 Head

The 1974 A13 engine for north america featured small oval ports.

H95 Small-Oval Shrouded-port Head

Used on all USA engines 1981-1982 (A12A, A14 and A15)
Intake: 37mm
Exhaust: 30mm
peanut-shaped combustion chambers
Small-oval ports, guide is shrouded
wet intake
14035-H8901 manifold gasket (same as Larg 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.

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.

Regular Oval Port

The A14/A15 Oval-port Heads include
* Intake: 37mm
* Exhaust: 30mm

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
H77: Same as H72 but drilled for more emission controls
H75: Same as H72 but for non-USA market
H89: Closed Chamber Wet manifold use in B310
M24: For twin-carb A14T, similar to H89 but with dual-valve springs

H72

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

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. The H72 head was common around 1977-1978. 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. EGR port in the exhaust ports.

Open Chamber design

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 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?

H75

A14: (H75) Oval Port, dry manifold, large valve A14S Sedan Coupe
* 11041-H7500 HEAD ASSY-CYLINDER A14S S,K B210
* 11041-H7502 HEAD ASSY-CYLINDER A14S V A10 Sedan Coupe -7803
** 11044-H7200 GASKET-MANIFOLD TO CYLINDER HEAD

Intake valves: 37mm 13201-H6200
Exhaust valves: 30mm 13202-H6200
Oval Ports
Intake-to-Head gasket 11044-H7200
Dry Intake
Open Chamber design, 31cc

H77

A14 H78 Oval Port Head

A14: (H78) Oval Port, dry manifold, large valve A14S Van
* 11044-H7860 GASKET-MANIFOLD TO CYLINDER HEAD
11041-H7860 HEAD ASSY-CYLINDER A14S V B210
11041-H7861 HEAD ASSY-CYLINDER A14S V A10 -7806

H89

A14 Oval-port "High Compression" was fitted to B310 Coupe and Sedan in the JDM market (but not to Van (wagon).

Closed Chamber
Oval Port
Intake Water Ports
New intake bolt pattern

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 11044-H7200
11041-M2460 HEAD ASSY-CYLINDER A14T B210 JDM

M49

Medium Oval Port

28x32 intake ports were used by A14E and A15E EFI heads.

H92

* Intake valves: 37mm 13201-H6200
* Exhaust valves: 30mm 13202-H6200 replaced by 13202-H8900 7910-
* Dual valve springs
* Medium Oval Ports with notch for injector
* Intake Water Ports
* B310 Asia markets
11041-H9200 HEAD ASSY-CYLINDER A14E N-7810 11041-H9201
11041-H9201 HEAD ASSY-CYLINDER A14E 7811-7903 11041-H9202
11041-H9202 HEAD ASSY-CYLINDER A14E 7904-7907 11041-H9204
11041-H9204 HEAD ASSY-CYLINDER A14E 7908-8010 
11041-H9204 HEAD ASSY-CYLINDER A15E 8011-
All of these are replacement-equivalents

Large Oval Port

H57

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

Competition Head

Intake: 35mm (optional 37mm)
Exhaust: 29mm (optional 30mm)

The Competition Head has the large oval ports and a small heart-shaped 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 has the A14 size valves, but is more accurately described as a ported and polished version of the standard A14 high-compression head.

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

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.

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

Reference: 1984 Nissan Competition Catalog

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?

Also see: Cylinder Head Modifications Raised-Ports.

Measuring Combustion Chamber Volume

Here's what you need:

A large syringe marked in CCs (without the needle, or remove the needle).
a piece of plexiglas, big enough to cover one cylinder. Drill a small hole about 6mm from edge of the plexiglas
some grease

Syringes are available from animal feed stores or your local chemist. Get a couple of syringes one thats about 20mls and one that has 0.1 increments which is normally about 3mls. That will cost $1-$2.

Here's how to measure:

place the head upside down as level as possible
put a small ring of grease around one of the combusion chambers
place the plexiglas over it and press it flat
Fill the syringe with water, and measure how many CCs it takes to fill the chamber

This is also a good way to tell if the valves are sealing well. It should hold water for several hours with no visible leak. If the water leaks out, it's time to lap the valves!

Dished pistons (factory A15)

Note that pistons came with different dishes according to year, country, etc.

Which Cylinder Head is "Best"?

The two main factors for peak horsepower:

combustion chamber design: closed chamber "heart-shaped" is more efficient than open chamber
port flow: oval is better than round for high-rpm use, and larger valves can be useful

NOTE: Don't confuse "open chamber" for a hemi-style chamber. Yes, both are 360-degree 'open', but the term "hemi" refers to valves at 45-degrees to each other (all A-type engines use valves parallel to each other). The "open" chamber is not inherently better flowing, but is used to reduce compression for lower NOx emissions.

Some say to start with the A12GX Engine head due to its high-compression chamber. Adding bigger valves is good for high-rpm power. Others say a ported standard A12 head will flow as much as the A12GX, but this doesn't increase the compression.

GX heads are not always easy to find, though they pop up for sale every year.

"The best head of the easily available variety, IMO is the H89 head from the A15." - A14Force.

Or you could use the H72 head, and shave/mill it to increase compression.

The A14GX (high-compression) head is probably the best all-around head: big valves, big ports and an efficient chamber design. But you probably cannot find this Competition head ... unless you already have one.

Aftermarket piston styles vary (flat-top or dished, and aftermarket popup/domed pistons). With dished pistons, the pistons can be shaved and the block milled (up to 0.090 inch) to make high compression "flat-top pistons".

On the other hand, for a supercharged motor low compression is best, because you can use more boost and gain more power than is lost due to the low compression.

closed chamber head with a half-dished piston is probably best due to the efficient "quench" combustion

For a low-rpm 'grunt' engine, or for maximum fuel economy, you'll want:

Small ports<
large valves with an A14 or A15, small stock-size valves with an A10 or A12 (anyone have another opinion?)
closed chamber or swirl-port head

So which is better for a street engine?

High compression engine: pay 15% premium for high-test fuel but get better mpg
Low compresion engine: buy the inexpensive petrol, but get worse mpg

Modifying a Head

See main article: Cylinder Head Modifications

See: Head Porting (Port and Polish)

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:

Retrieved from "http://datsun1200.com/modules/mediawiki/index.php?title=A-series_Cylinder_Heads"

A-series Cylinder Heads

Revision as of 05:22, 7 June 2010

Contents

Cylinder Head Identification

Head Types

Distinguishing Features

Oil passage in the head

Interchanging

Combustion Chamber

Chamber Size

Intake Ports

Port Sizes

Intake Manifolds

Intake/Exhaust manifold bolt pattern

Valve Springs

Valve sizes

Nissan Competition

Coolant Passages

Early A Engine

Round Port

A10 head

B10 Coupe Head

A10 M01 Head

A12 H10 Head

A12 H15 Head

A12 H39 Head

Large Oval Port

A12GX Head

Early A12T Head

Late A Engine

Round Port

H74

A12 M30 Head

A12 G25 Head

G32

A12 G61 Head

A14 FU Round Port head

A14 FU High-Swirl head

H85

A14 H78 Round Port Head

Small Oval Port

A13 H62 Head

H95 Small-Oval Shrouded-port Head

Regular Oval Port

H72

H75

H77

A14 H78 Oval Port Head

H89

M24

M49

Medium Oval Port

H92

Large Oval Port

H57

Competition Head

Other heads

High Roof Heads

Measuring Combustion Chamber Volume

Which Cylinder Head is "Best"?

So which is better for a street engine?

Modifying a Head

Part Numbers

DOHC Heads for A-series

AY12 Racing Head