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The A12 engine of the Datsun 1200 features a modern lightweight cast-iron cylinder block.
Also see Block Comparison
Contents |
Identification
A12 Engine ID Mark
Ventilation
Under the block breather pipe, this steel mesh separates out the oil vapor from crankcase ventilation air.
Block Height
A10 Deck Height: 179.1mm A12/A12A Deck Height: 189.1mm A14/A15 Deck Height: A12 height 204.1mm
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.
Also see: 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
Part Numbers
USA
B110 RAW LIST
12100-H1000 ASSY-CONNECTING ROD
12109-H1001 BOLT-CONNECTING ROD (TOKYO RASI) 12109-H1011 BOLT-CONNECTING ROD (TOKAI SEIAT 12112-18000 NUT-HEX CONNECTING ROD 12111-20906 BUSHING-CONNECTING ROD UNDERSIZE 100 12111-20910 BEARING-CONNECTING ROD STD 12111-20900 BEARING-CONNECTING ROD STD 12111-20901 BUSHING-CONNECTING ROD UNDERSIZE 8 12111-20902 BUSHING-CONNECTING ROD UNDERSIZE 12 12111-20903 BUSHING-CONNECTING ROD UNDERSIZE 25 12111-20905 BUSHING-CONNECTING ROD UNDERSIZE 75 12111-20904 BUSHING-CONNECTING ROD UNDERSIZE 50