STANDARDISATION OF M14, 16 mm HEXAGON SIZE SPARK PLUGS TO ISO STANDARD

Until recently, there was no restriction on spark plug design relating to the dimension from the gasket seat to the terminal nut.

At the ISO Conference in 1988, this dimension was standardised for M14, 16 mm smaller from the top of the terminal nut to the gasket position.

1. Appearence and Size

As shown in the following figure, the ISO design is 2.5 mm smaller from the top of the terminal nut to the gasket position.

2. INDICATION of ISO Type Spark Plugs

NGK Spark Plug Co. LTD. use a horizontal line, located under the product number on the insulator, to identify an ISO spark plug.

                        

In addition, several design symbols are employed.

           Old Type                       I.S.O.

     BCPR ---- Series         BKR ----Series
     ZFR    -  A Series         ZFR   - F Series
     PFR    -  A Series         PFR  - B Series

I.S.O type plugs are shown in the NGK catalogue.

3. Interchangeability Between ISO and Old Type

    The table below also applies to ZFR and PFR type.