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The crankshaft is interchangeable between early A12, A12GX, late A12, late A13 and A12A. Only the flywheel bolts differ, using metric bolts starting with the A-engine Redesign.

1 Overview
2 Flywheel Bolts
3 Misc
4 Identification
- 4.1 H10
- 4.2 H85
5 Crankshaft Pulley
6 Lightened Crankshaft
7 Counterweighted Cranks
8 Seals
9 Oil Thrower
10 Specs
11 Part Numbers
12 Damage
- 12.1 Flywheel Loosening
- 12.2 Cracked Crank

[edit]

Overview

Album 17133

All Datsun A-series crankshafts are forged, and stroke comes in four sizes:

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

Crankshaft Stroke:

Bare crank
Album 30408

Timing Chain sprocket fits over the snout
Album 30409

[edit]

Flywheel Bolts

The flywheel bolts are special washerless bolts, do not use generic bolts.

Buy at Bprojects
Album 26245

* 3/8 inch bolts: 1966-1973 crank uses Imperial system 3/8" x 24 UNF bolts
* 10mm bolts: 1974-up crank uses Metric M10 1.25 bolts (from '73-7)

12315-H1001 BOLT-FLY WHEEL 6 B110 MANUAL $4.38 
12315-H1000 BOLT-FLY WHEEL 6 B110 AUTOMATIC $3.51 
12330-20300 PILOT-CONVERTER B110 AUTOMATIC $18.66 
12333-20300 PLATE-CRANK CONVERTER B110 AUTOMATIC $9.44

Hex head: 14 mm
Thread length: 20mm
Head bottom length: 22mm
Whole length: 29mm

1966-1973: crank uses english-system 3/8" x 24 UNF bolts 
* 12315-18001 BOLT-flywheel & drive plate 6 A10 (requires washers)
** 12314-18001 WASHER-flywheel for A10 only
** 12314-18002 WASHER-flywheel (from engine # A10-87871)
* 12315-H1001 BOLT-FLYWHEEL 6 MANUAL (3/8", uses no washers)
* ARP bolts - buy at Bprojects
* Will ARP 206-2802 work? For BMC A-series engines
  (UHL Under Head Length 0.900") $18 USD/set of 6
* Pitroad-ARP bolts

1974-up: crank uses Metric M10 x 1.25 bolts (from '73-7)
* A12,A13,A14,A12A,A15
* 12315-H6900 BOLT-FLYWHEEL 6 (10mm) $4.83 USD > 12315-H6200
* Will ARP 203-2802 work? For 4AGE engines 
  (UHL Under Head Length 1.050") $22 USD/set of 8

26 Washer for A10 flywheel bolts only (6 needed)
Album 26242

Imperial flywheel bolts - heads unmarked
Album 26244

'62' bolts for metric cranks
Album 26243 Album 23498

[edit]

Misc

Also see: Bored And Stroked for crankshaft modifications you can perform at home.

Twin-carb engine (A12GX, A12T and A14T) crankshafts are the same as a standard engines.

1974-up cranks use metric flywheel bolts. Early engines used British threads. See A Engine Redesign

Apparently there are two forgings of crankshaft:

Heavy duty
Album 18244

Light weight: thinner counterweights that also have small scallops out of them. Late model factory crank (from B310 Sunny)
Album 17135

Front bolt, that holds the front pulley on, is: 
* Part Number: 12309-78200 ($4.58) 
* M16 x 1.50 (fine) pitch 
* 15mm diameter 
* 27mm long 
* The head is ?mm hex and about 15 mm thick. 
* Torque specification: 15-16 kg/m (108-116 ft. lb.)

[edit]

Identification

A12: 70mm H50 & H10 straight crank throws
Album 18244

A12/A13 H85 70mm scalloped crank throws
Album 17135

A14 77mm H62 1973-1978 straight crank throws

Main: A14 Crankshaft

A14 77mm H89 scalloped crank throws 1979-
Album 14241

A15 12200-G3400 MT, 12200-H9700 AT

[edit]

H10

A12 70mm H50 & H10

12200-H1000/12200-H1001 -7909
12200-H5000/12200-H5001

Album 18244

[edit]

H85

A12/A13 70mm scalloped crank throws (9.51 kg) lightweight but strong

12200-H8560/12200-H8500 7910- > (can replace) 12200-H5001

Album 17135

Album 18243 Album 17136

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Crankshaft Pulley

Main: Crankshaft Pulley

[edit]

Lightened Crankshaft

Discussion: ^POST JTS Cranks

Race-prepped cranks are often:

Relieved/polished to reduce chance of cracking
Lightened for quicker acceleration
Knife-edge for reduced windage friction

Race-prepped A-series crank:
Album 7306 Album 19814 Album 5538 Album 8478 Album 8479 Album 8617 Album 9665

A12 crank lightened & edged

A14 knife-edged

[edit]

Counterweighted Cranks

All A-series crankshafts are counterweighted and will rev smoothly to 8500+ RPM.

Stock crank is counterweighted: there are four counterweights, one for each crank throw:
Album 17133

A12 "fully" counterweighted billet Pitroad A12 Crankshaft☁
☁

Fully counterweighted means each journal has two counterweights. Theoretically it means better torsional vibration control. A regular counterweighted crank accelerates faster and has less friction, so a heavier fully counterweighted crank should only be used where torsion vibration is a known problem.

Here is the difference between counterweighted and "fully counterweighted" (L/Z cranks shown): ^POST Lseries Power Time

Either way, both types of Datsun cranks are precision balanced from the factory.

Smaller counterweights == smaller crankcase

The E16 crank has a much larger stroke, so it uses two counterweights per crank throw, which helps reduce the overall diameter of the crank.

Of full counter crank benefits advantageous to the vibration reduction high-speed and high output, disadvantage weight increase and manufacturing cost. Crankshaft for race for achieving both the lightweight and stiffness UP is

[downside] 800 g weight increase

Album 23985 Album 23984

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Seals

Main: Crankshaft Seal

[edit]

Oil Thrower

The thrower (oil slinger) goes over the front snout of the crank, after the Timing Chain set is placed, and before the Timing Cover is installed/

The slinger's job is to keep oil away from the crankshaft oil seal. The cupped side faces the timing chain to "throw" oil back towards the chain.

12302-18000ᴳ THROWER-OIL CRANKSHAFT 1 A12 - $1.57
Album 28574 Album 28575

timing chain sprocket and OIL THROWER. The curved side goes toward the block, flat side toward the front.
Album 30407

[edit]

Specs

from 1973 Datsun 1200 Service Manual Figure EM-58 Crankshaft
Main journal diameter  49.951-49.964 mm
Main journal width     27.00-27.05 mm
crankpin diameter      44.961-44.974 mm

[edit]

Part Numbers

12200-H5000 CRANKSHAFT A12
12200-H8500 CRANKSHAFT ASSY B310 A12S, A13S 
12200-H8515 A12/A12A CRANKSHAFT 70mm/2.76" stroke
12200-H5720 A12 COMPETITION CRANKSHAFT 70mm/2.76" stroke
12200-H8915 A13/A14 CRANKSHAFT 77mm/3.03" stroke
* Weight 26.2 lbs
12200-G3400 A15 CRANKSHAFT 82mm/3.23" stroke

Old Numbers:
12200-H1000 ASSY-CRANKSHAFT 1 A12 MANUAL - $624.02 
12200-H1001 CRANKSHAFT 1 A12 -671 12 12200-H1000 superceded 
12200-H1000 CRANKSHAFT 1 A12 0671- 2 12200-H1001 superceded 
12200-H5000 CRANKSHAFT 1 A12 0572- 2 12200-H1000 $624.02

BEARINGS

Main: Bearings

SEAL, Front

Main: Crankshaft Seal

SEAL, Rear

Main: Crankshaft Seal

PILOT BUSHING

Main: Pilot Bushing

OIL SLINGER: see #Oil Thrower

FLYWHEEL BOLTS: see #Flywheel Bolts

[edit]

Damage

[edit]

Flywheel Loosening

The Datsun factory balanced every engine. But when parts are changed, it will get out of balance. In worst case scenario, this leads to shaking and eventual loosening of the flywheel bolts.

I started to hear a hell of a noise and shaking under acceleration and reving ... the flywheel bolts have given up the ghost.

For best practices, see #Flywheel Bolts.

[^POST Flywheel bolts failure\fix\questions
Album 24122 Album 24123 Album 24124

[edit]

Cracked Crank

All A-series crankshafts are forged, but can still crack if abused.

Causes:

Dropping the crank during or before engine assembly
Unbalanced engine. After replacing a piston, a rod or the crank, have the engine re-balanced
Pinging (detonation) can put massive stresses on the engine

The thick forging line can be seen in this photo
Album 19917 Album 19916

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Crankshaft

Current revision

Contents

Overview

Flywheel Bolts

Misc

Identification

H10

H85

Crankshaft Pulley

Lightened Crankshaft

Counterweighted Cranks

Seals

Oil Thrower

Specs

Part Numbers

Damage

Flywheel Loosening

Cracked Crank