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[Datsun 1200 encyclopedia]


From Datsun 1200 Club

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Category: Engine Mechanical

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.



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:


Flywheel Bolts

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

Buy at Bprojects
26245.jpgAlbum 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 
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)
26242.jpgAlbum 26242

Imperial flywheel bolts - heads unmarked
26244.jpgAlbum 26244

'62' bolts for metric cranks
23498.jpgAlbum 23498 26243.jpgAlbum 26243


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

  • 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

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

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.)


A12: 12200-H5000/12200-H5001 < 12200-H1000/12200-H1001 -7909
18244.jpg th_crank.jpg th_Crankshaft1.jpg th_Crankshaft2.jpg th_Crankshaft3.jpg

A12/A13 70mm 9.51 kg scalloped crank throws, 12200-H8560/12200-H8500 7910- <2,0> 12200-H5001
17135.jpg 17136.jpg 18243.jpg

A14 H62 12200-H6200 starting 1973 -7909
th_A14CrankshaftH6240.jpg th_A14Crankshaft1.jpg 8966.jpg 8967.jpg 11418.jpg

A14 H89, scalloped crank throws, 12200-H8900 starting 0879 <> 12200-H6200
25674.jpg 25673.jpg 3949.jpg 3950.jpg 14241.jpg 14535.jpg 17137.jpg th_G34.jpg th_a14-crank.jpg th_H89-crank.jpg

G34 block with scalloped crankshaft


A15 12200-G3400 MT, 12200-H9700 AT
A15crank-1.jpg A15crank-2.jpg

M23 F10
M49 F10

Crankshaft Pulley

See Crankshaft Pulley

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:
19814.jpgAlbum 19814 5538.jpgAlbum 5538 7306.jpgAlbum 7306 8478.jpgAlbum 8478 8479.jpgAlbum 8479 8617.jpgAlbum 8617 9665.jpgAlbum 9665

A12 crank lightened & edged

A14 knife-edged
A14_crank-1.jpg A14_crank-2.jpg

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:

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):

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

23985.jpgAlbum 23985 23984.jpgAlbum 23984


Oil Thrower

The thrower goes over the front snout of the crank, before the Timing Cover and Crankshaft Pulley are installed
28574.jpgAlbum 28574 28575.jpgAlbum 28575


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

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 
* See main article: Bearings
SEAL, Front
See main article: Crankshaft Seal
SEAL, Rear
See main article: Crankshaft Seal
* see Pilot Bushing
12302-18000 THROWER-OIL CRANKSHAFT 1 A12 - $1.57 
FLYWHEEL BOLTS - see Crankshaft#Flywheel Bolts


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.

Flywheel bolts failure - crank now needs repair
24122.jpg 24123.jpg 24124.jpg

Cracked Crank

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


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

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

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