If switching from the stock platinum spark plug to either a resistor or non-resistor plug, then attention needs to be paid to the spark gap.Ī higher voltage spark can cause more-complete combustion and therefore increase cylinder pressure and produce more power. If you can use a non-resistor spark plug, then the 'racing' plugs listed in the gray area of the table below are also an option. Because the standard 13/16' socket does not fit in the spark plug well in the cylinder head, we cannot use spark plugs with a 13/16' (20.6-mm) hex size made by NGK (such as BPR6ES, BPR7ES, BPR8ES, etc.) and the other manufacturers. At this time, there are no heat range 8 or colder resistor-type plugs available in a 5/8' hex, 14-mm thread, and 19-mm reach. The reddish colored areas show one heat range hotter, and the bluish colored areas show one heat range colder. The greenish colored areas in the table show the available replacements in the same heat range as the factory plugs. The selection of replacement spark plugs is somewhat limited from the other major manufacturers, which include AC Delco, Autolite, Bosch, Champion, and Motorcraft (the problem is either the hex size or lack of a resistor). NGK and Denso spark plugs are available online at the stores listed below. While NGK plugs are probably the easier of the two to obtain, they both can be hard to find at the corner auto parts store.

The stock spark plug for the turbocharged, DOHC, 6G72 engine is NGK PFR6J-11 or Denso PK20PR-P11, which have platinum-tipped electrodes. X 1.1-mm (0.043') spark gap (missing letter means not pre-gapped)Ĭ 14-mm thread, 5/8' hex shell, 3/4' reachĨ Heat range (8 and 9 are medium, 10 is hotter, 7 is colder)Ĥ wide spark gap required for Federal and California standards (missing number means not pre-gapped) PK 14-mm thread, 5/8' hex shell, 19-mm reach, platinum tipsĢ0 Heat range (20 is medium like NGK 6, 16 is hotter, 22 is colder)ġ1 1.1-mm (0.043') spark gap (missing number means not pre-gapped)ħ Heat range (7 and 6 are medium, 8 is hotter, 5 is colder)ĭ 3/4' reach, 3-mm projected insulator noseĬ copper-core center electrode (P is for platinum-core) S Standard 2.5-mm diameter center electrode with copper coreĢ4 Heat range (24 is medium like NGK 6, 22 is hotter, 27 is colder) 11 1.1-mm (0.043') spark gap (missing number means not pre-gapped) My Spark Plug Tech web page is at 2-sparkplugtech.htm.į 14-mm thread, 19-mm reach, 5/8' hex shellĦ Heat range (6 is medium, 5 is hotter, 7 is colder) The recommended spark plug is the NGK BPR5ES-11 or the Denso W16EPR11.

Note: The SOHC 6G72 engine uses 13/16' hex-shell spark plugs. For complete part number keys refer to:Īutolite: misc/autolite_sparkplugnumberingsystem.pdfīosch: misc/bosch_sparkplugs_designationcodes.gifīosch: misc/bosch_sparkplugs_designationcodes.jpgĬhampion: misc/champion_sparkplugs_designationcodes.jpg The NGK, Denso, Bosch, and Champion part numbers are partially explained below. Stealth 316 - 3S Spark Plug Cross Reference Guide Spark Plug Cross Reference Guide

Bosch spark plug cross reference