From Datsun 1200 Wiki

The A12 engine in the Datsun 1200 uses traditional coil springs for each valve. The A12GX Engine uses dual springs on each valve.

Specs and Testing

 (http://datsun1200.com/modules/myalbum/photo.php?lid=15332)

• Free Length: 46.5 mm (1.831 in)
• Valve Closed: 38.7 mm at 23.9 kg (1.524 in at 52.7 lb)
• Valve Open: 30.2 mm at 58.5 kg (1.19 in at 129 lb)

1. Measure the free length and the tension of each spring. If the measured value exceeds the specified limit, replace the spring.
2. Check each spring for deformation with a square. Any springs with a deflection of 1.6 mm (0.0630 in) or more must be replaced.

Part Numbers

Nissan Part Numbers

• 13203-H1000 SPRING-valve, outer ALL except GX
• 13205-18000 SEAT-valve spring ALL except GX
• 13209-H2301 RETAINER-valve spring ALL
• 13210-73400 COLLET-valve
• 13210-H1000 COLLET-valve (from 72-2)
• 13210-U0100 COLLET-valve (from 71-10)
  • All three collet PNs interchange
• 13219-H1000 SHROUD-valve, inner ALL except GX

GX-specific

• 13203-H2300 SPRING-valve, outer GX
• 13203-H2301 SPRING-valve, inner GX
• 13205-H2300 SEAT-valve spring GX
• 13207-H2300 SEAL-oil, valve GX superceded
• 13207-H2301 SEAL-oil, valve GX (from 72-7)
• 13207-H2310 SEAL-oil, valve GX (from 72-10)