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Revision as of 16:37, 14 March 2009
A12 Engine ID Mark
Contents |
Cylinder Blocks
- 11010-H2300 A12 BARE BLOCK 73mm/2.87" bore size
- 11010-H9960 A12A BARE BLOCK 75mm/2.95" bore size
- 11010-H6200 [1974] A13 BARE BLOCK 73mm/2.87" bore size
- 11010-H9700 A14/A15 BARE BLOCK 76mm/2.99" bore size
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-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
ROD BOLT
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
- 12112-H1000 CONNECTING ROD NUT
CONNECTING ROD 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"
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