# How to read a Magneti Marelli spark plug reference

> A Magneti Marelli short code encodes the range, the electrode type, the thread & hex size, the heat grade and the gap. Here is how to decode it.

A Marelli code such as **SNB7001-9** reads: **S** (range) · **N/I/P** (type) · **A/B/D/E** (thread × hex) · **heat grade** · progressive number · **-gap**.

## 1. Type of electrode

- **N** — nickel
- **I** — iridium
- **P** — platinum

## 2. Thread size × hexagon

LetterThreadHex
A14 mm20.8 mmB14 mm16 mm
D12 mm16 mmE12 mm14 mm

## 3. Heat grade

The heat grade tells how well the plug sheds heat: **low numbers = hot** (low-power engines), **high numbers = cold** (high-power engines). Marelli grade vs others (approx.): Marelli 2 ≈ NGK 2 / Bosch 10 / Denso 9; Marelli 6 ≈ NGK 6 / Bosch 7 / Denso 20; Marelli 10 ≈ NGK 10 / Bosch 2 / Denso 31.

## 4. Progressive number

A sequential number identifying the specific type within the range.

## 5. Gap

The number after the dash is the pre-set **gap** in tenths of a millimetre (**-9** = 0.9 mm, **-11** = 1.1 mm).

## 6. Tightening torque

Torque depends on the seat, thread diameter and cylinder-head material. Flat seat (with gasket): 12 mm 15–25 N·m (iron) / 15–20 (alu), 14 mm 25–35 / 25–30. Always follow the value printed on the box.

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*Source : [How to read a Magneti Marelli spark plug reference](https://www.thesparktwin.com/en/guide/nomenclature-marelli/) — TheSparkTwin*