# Valve length — standard and minimum (NA6)

Canonical URL: https://miatatorque.com/spec/valve-length-na6/

Applicability: NA 1990–1993 (B6) — Other years inferred from 1990 factory evidence.

Confidence: fsm

Length
Standard
IN: 105.29 mm (4.1452 in)
EX: 105.39 mm (4.1492 in)
Minimum
IN: 104.79 mm (4.1256 in)
EX: 104.89 mm (4.1295 in)

Always confirm against your factory manual. Match every restriction and follow all stages and procedure notes. Disputed claims must not be automatically resolved. The complete record below preserves every printed unit, source claim and procedure.

```json
{
  "id": "valve-length-na6",
  "name": "Valve length — standard and minimum (NA6)",
  "aliases": [],
  "applies_to": [
    {
      "gen": "NA",
      "years": [
        1990,
        1993
      ],
      "engines": [
        "B6"
      ],
      "note": "Other years inferred from 1990 factory evidence."
    }
  ],
  "kind": "non-torque",
  "value_text": "Length\nStandard\nIN: 105.29 mm (4.1452 in)\nEX: 105.39 mm (4.1492 in)\nMinimum\nIN: 104.79 mm (4.1256 in)\nEX: 104.89 mm (4.1295 in)",
  "procedure": {
    "notes": "IN means intake; EX means exhaust. Measure overall valve length."
  },
  "confidence": "fsm",
  "sources": [
    {
      "source": "fsm-1990",
      "page": "B–49 (PDF p. 76)",
      "as_printed": "Length\nStandard\nIN: 105.29mm (4.1452 in)\nEX: 105.39mm (4.1492 in)\nMinimum\nIN: 104.79mm (4.1256 in)\nEX: 104.89mm (4.1295 in)",
      "verified_years": [
        1990,
        1990
      ],
      "document": {
        "id": "fsm-1990",
        "tier": 1,
        "title": "1990 Mazda MX-5 Miata Workshop Manual",
        "part_number": "1193-10-89C",
        "covers": [
          {
            "gen": "NA",
            "years": [
              1990,
              1990
            ],
            "engines": [
              "B6"
            ]
          }
        ],
        "url": "https://archive.org/details/1990-mazda-mx-5-miata-workshop-manual_202411"
      }
    }
  ],
  "jobs": [],
  "system": "engine",
  "component": "inventory-pass-2026-10",
  "componentName": "Service measurements and fasteners",
  "sequence_diagrams": [],
  "url": "https://miatatorque.com/spec/valve-length-na6/"
}
```