# Piston diameter by size (NA8)

Canonical URL: https://miatatorque.com/spec/piston-diameter-na8/

Applicability: NA 1994–1997 (BP) — Other years inferred from 1994 factory evidence.

Confidence: fsm

Piston diameter
mm {in}
Standard 82.954—82.974 {3.2660—3.2666}
0.25 {0.010} oversize 83.211—83.217 {3.2761—3.2762}
0.50 {0.020} oversize 83.461—83.467 {3.2859—3.2861}

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": "piston-diameter-na8",
  "name": "Piston diameter by size (NA8)",
  "aliases": [],
  "applies_to": [
    {
      "gen": "NA",
      "years": [
        1994,
        1997
      ],
      "engines": [
        "BP"
      ],
      "note": "Other years inferred from 1994 factory evidence."
    }
  ],
  "kind": "non-torque",
  "value_text": "Piston diameter\nmm {in}\nStandard 82.954—82.974 {3.2660—3.2666}\n0.25 {0.010} oversize 83.211—83.217 {3.2761—3.2762}\n0.50 {0.020} oversize 83.461—83.467 {3.2859—3.2861}",
  "procedure": {
    "notes": "Measure at right angle to piston pin, 16.5 mm {0.650 in} below lower edge of oil-ring groove. Replace rings when replacing piston."
  },
  "confidence": "fsm",
  "sources": [
    {
      "source": "fsm-1994",
      "page": "B–55 (PDF p. 92)",
      "as_printed": "Piston diameter\nmm {in}\nStandard 82.954—82.974 {3.2660—3.2666}\n0.25 {0.010} oversize 83.211—83.217 {3.2761—3.2762}\n0.50 {0.020} oversize 83.461—83.467 {3.2859—3.2861}",
      "verified_years": [
        1994,
        1994
      ],
      "document": {
        "id": "fsm-1994",
        "tier": 1,
        "title": "1994 Mazda MX-5 Miata Workshop Manual",
        "covers": [
          {
            "gen": "NA",
            "years": [
              1994,
              1997
            ],
            "engines": [
              "BP"
            ]
          }
        ],
        "note": "Mazda's base manual for 1994–97; later model years got supplements, which we haven't checked yet."
      }
    }
  ],
  "jobs": [],
  "system": "engine",
  "component": "inventory-pass-2026-10",
  "componentName": "Service measurements and fasteners",
  "sequence_diagrams": [],
  "url": "https://miatatorque.com/spec/piston-diameter-na8/"
}
```