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Revision as of 02:48, 10 July 2010

The A12 engine of the Datsun 1200 features a modern lightweight cast-iron cylinder block.

Also see Block Comparison

1 Identification

Identification

A12 Engine ID Mark

Block Height

A10 Deck Height: 179.1mm (?) 
A12/A12A Deck Height: +10mm 
A14/A15 Deck Height: A12 height +15mm

Cylinder Blocks

A12 Deck Height: 189.1mm (?)

~2.5 liter coolant capacity

The A10 block is 10mm shorter than A12 block, while A14/A15 block is 15mm taller than A12 block. Length is the same for a A-series engine blocks.

Block Comparison

Original Block

H10 or M08 block castings

* 11010-H2300 A12 BARE BLOCK 73mm/2.87" bore size

Redesigned Block

11010-H5000 A12 73mm bore size
11010-G1600 A12 From June 1975 (?)
11010-G1618 A12 B120 7908-8503
11010-G1619 A12 B120 8504-
M79 casting
11010-H9960 A12A BARE BLOCK B310 75mm/2.95" bore size
11010-H8500 Sedan, Coupe B310 -8010
11010-H9463 Van B310 8011-8109, 8110-

M79 casting, from late 1200 Sunny Truck

Tall Block

Deck height: 204.1mm (?), or 15mm taller than an A12/A12A block. Length is the same.

11010-H6200 [1974] A13 BARE BLOCK 73mm/2.87" bore size
A14 cast "A14" above fuel pump
- H72 or G30
11010-H9700 A14/A15 BARE BLOCK 76mm/2.99" bore size
- G34

Overbore

The 1971-1973 A12, the one with the front distributor, can usually be bored to 76mm. This is the same as a stock A14. There are probably some dud blocks around, but generally 76mm is fine. Pistons of 76.5 mm size and larger were offered through the Datsun competition department and others back in the 70's, so it's a factory approved bore size.

A14 pistons use a 19mm wrist pin while the A12 rods have a 17.5mm hole, so you have choices:

Bore the original rod to 19mm. This is most commonly done
Find a set of late A12 rods. There seems to have been a change in the later rods and these forgings look like they are the ones that were used for the A12A & A13 engines. [more on this later]. These rods have more 'meat' around the pin hole & would be stronger than a 1200 rod after the pin hole was bored to 19mm.
Find a set of A12A or 1980's A13 rods as these have the right length and the correct wrist pin hole for the A14 pins

73mm bore piston used the 17.5mm piston pin diameter:

A10
1971-1973 A12 (1200)
1974-up A12
1974 A13 (tall block engine)

A series pistons for engines with 75mm bore used a 19mm pin:

A12A - USA & Japan only

76mm bore size also used the 19mm pin:

A14
A15
1979-'81 (Asia only)

A12A and late A13s were just bored out A12s, so they had the shorter A12 length rods, but with the bigger pin size. The crankshaft is interchangeable between early A12, late A12, late A13 and A12A.

Crankshafts

Stroke:

70mm (2.76 in.) stroke: A12/A12A/A13(1980)
77mm (3.03 in.) stroke: A13(1974)/A14
82mm (3.23 in.) stroke: A15

For more details and part numbers, see Crankshaft

Connecting Rods

4 of each required:

12100-18000 A10 ASS'Y-ROD, connecting 117.5mm
12100-H1000 A12 CONNECTING ROD 121.5mm/4.78" center-to-center
12100-18500 A12A CONNECTING ROD 121.5mm/4.78" center-to-center
12100-16200 [1974] A13 CONNECTING ROD 133mm/5.24" center-to-center
12100-17200 A14/A15 CONNECTING ROD 133mm/5.24" center-to-center

The weights of the 4 stock A15 rods with ARP rod bolts and nuts installed, no bearings is: 514.00 to 511.81 grams.

Bearings

The -25720/-H2310 bearing shell produces the most desirable bearing clearance for racing purposes when applied to a standard size crankshaft. The other shells exist in order to obtain proper clearance when compensating for the variations in the crankshaft or connecting rod journals.

8 each required:

12111-25720 .0590"
12111-25721 .0588"
12111-25722 .0585"
12111-25723 .0592"
12111-25724 .0583"

Rod Studs

The same rod studs are used by all A-series engines, from A12 to A15.

The Datsun rod bolt is a true stretch bolt and should be torqued only once. New bolts should be installed at every disassembly. 8 each required:

12109-H1001 CONNECTING ROD BOLT TOKYO RASI $3.63 USD
- superceded 12109-18000 BOLT-connecting rod
12109-H1011 CONNECTING ROD BOLT TOKYO SEATI
- alternate supplier
12112-H1000 NUT-HEX CONNECTING ROD $1.47 USD
- superceeded 12112-18000 or 89-11238

ARP Brand connecting rod stud set

102-6002 about $60 USD [compared to about $32 from Nissan]

Weight

For maximum performance, use the lightest rod that will hold up to the intended usage. Stock A-series rods are forged, and will last a lifetime in a stock or moderately upgraded performance engine. There is no need to use a heavier duty rod unless you are using a high boost turbo or supercharger, or revving higher than 8500 RPM.

For road racing engines with sustained high-RPM loads, a heavier duty rod may be required.

The weight of a stock A15 rod with ARP rod bolts and nuts installed, no bearings is:

Approximately 514 grams

Pistons

A12 engine came with dished pistons for approximately 9.0:1 compression ration. Standard bore size for the A12 or A13 block is 73mm/2.874". Pistons are cast. Nissan Competition does not recommend forged pistons for street use.

See main article: Piston

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Engine block