Crank
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.
Overview
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:
http://i297.photobucket.com/albums/mm219/ddgonzal/Datsun%201200/wiki/14241.jpg
Flywheel Bolts
The flywheel bolts are special washerless bolts, do not use generic bolts.
Buy at Bprojects
* 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)
Imperial flywheel bolts - heads unmarked
'62' bolts for metric cranks
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
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.)
Identification
A12: 12200-H5000/12200-H5001 < 12200-H1000/12200-H1001 -7909
http://i297.photobucket.com/albums/mm219/ddgonzal/Datsun%201200/wiki/th_crank.jpg http://i237.photobucket.com/albums/ff245/chrislyons8/th_Crankshaft1.jpg http://i237.photobucket.com/albums/ff245/chrislyons8/th_Crankshaft2.jpg http://i237.photobucket.com/albums/ff245/chrislyons8/th_Crankshaft3.jpg
A12/A13 70mm 9.51 kg scalloped crank throws, 12200-H8560/12200-H8500 7910- <2,0> 12200-H5001
A14 H62 12200-H6200 starting 1973 -7909
http://i297.photobucket.com/albums/mm219/ddgonzal/Datsun%201200/wiki/th_A14CrankshaftH6240.jpg http://i297.photobucket.com/albums/mm219/ddgonzal/Datsun%201200/wiki/th_A14Crankshaft1.jpg 
A14 H89, scalloped crank throws, 12200-H8900 starting 0879 <> 12200-H6200
http://i297.photobucket.com/albums/mm219/ddgonzal/Datsun%201200/wiki/th_G34.jpg http://i297.photobucket.com/albums/mm219/ddgonzal/Datsun%201200/wiki/th_a14-crank.jpg http://i297.photobucket.com/albums/mm219/ddgonzal/Datsun%201200/wiki/th_H89-crank.jpg
G34 block with scalloped crankshaft
A15 12200-G3400 MT, 12200-H9700 AT
http://i297.photobucket.com/albums/mm219/ddgonzal/Datsun%201200/wiki/A15crank-1.jpg http://i297.photobucket.com/albums/mm219/ddgonzal/Datsun%201200/wiki/A15crank-2.jpg
A14 M23 F10 M49 F10
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:
A12 crank lightened & edged
http://img.photobucket.com/albums/ff245/chrislyons8/Red%20B10/3.jpg
A14 knife-edged
http://i297.photobucket.com/albums/mm219/ddgonzal/Datsun%201200/wiki/A14_crank-1.jpg http://i297.photobucket.com/albums/mm219/ddgonzal/Datsun%201200/wiki/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):
http://i85.photobucket.com/albums/k45/b120dat/Picture175.jpg
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
Seals
Main: Crankshaft Seal
Oil Thrower
The thrower goes over the front snout of the crank, before the Timing Cover and Crankshaft Pulley are installed
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
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 * See main article: Bearings
SEAL, Front See main article: Crankshaft Seal
SEAL, Rear See main article: Crankshaft Seal
PILOT BUSHING * see Pilot Bushing
SLINGER 12302-18000 THROWER-OIL CRANKSHAFT 1 A12 - $1.57
FLYWHEEL BOLTS - see Crankshaft#Flywheel Bolts
Damage
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
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
- Detonation (pinking) can put massive stresses on the engine
The thick forging line can be seen in this photo
