Spark Plug Cross Reference Guide
for the DOHC 6G72 Engine in the
Mitsubishi 3000GT and Dodge Stealth

by Jeff Lucius

Part Numbers and Cross Reference Guide

NGK logo The NGK, Denso, Bosch, and Champion part numbers are partially explained below. For complete part number keys refer to:
Autolite: misc/autolite_sparkplugnumberingsystem.pdf
Bosch: misc/bosch_sparkplugs_designationcodes.gif
Bosch: misc/bosch_sparkplugs_designationcodes.jpg
Champion: misc/champion_sparkplugs_designationcodes.jpg
Denso: http://www.densoiridium.com/identifyplugs.php
NGK: misc/ngk-partnumberkey.pdf

Note: The SOHC 6G72 engine uses 13/16" hex-shell spark plugs. The recommended spark plug is the NGK BPR5ES-11 or the Denso W16EPR11.

My Spark Plug Tech web page is at 2-sparkplugtech.htm.

NGK PFR6J-11
  P   Platinum tips
  F   14-mm thread, 19-mm reach, 5/8" hex shell
  R   Resistor type
  6   Heat range (6 is medium, 5 is hotter, 7 is colder)
  J   ISO projected insulator nose
-11  1.1-mm (0.043") spark gap (missing number means not pre-gapped)

NGK BCPR6ES-11
  B   14-mm thread
  C   5/8" hex shell
  P   JIS Projected insulator nose
  R   Resistor type
  6   Heat range (6 is medium, 5 is hotter, 7 is colder)
  E   19-mm reach
  S   Standard 2.5-mm diameter center electrode with copper core
-11  1.1-mm (0.043") spark gap (missing number means not pre-gapped)

Denso IK24ER-U11
   I   Iridium power plug
  K   14-mm thread, 5/8" hex shell
24   Heat range (24 is medium like NGK 6, 22 is hotter, 27 is colder)
  E   ISO projected insulator nose
  R   Resistor type
 -U   U-groove center electrode
11   1.1-mm (0.044") spark gap

Denso PK20PR-P11
PK   14-mm thread, 5/8" hex shell, 19-mm reach, platinum tips
20   Heat range (20 is medium like NGK 6, 16 is hotter, 22 is colder)
  P   ISO projected insulator nose
  R   Resistor type
 -P   Platinum tipped plug for DIS
11   1.1-mm (0.043") spark gap (missing number means not pre-gapped)

Bosch FR7DCX
  F   14-mm thread, 5/8" hex shell
  R   Resistor type
  7   Heat range (7 and 6 are medium, 8 is hotter, 5 is colder)
  D   3/4" reach, 3-mm projected insulator nose
  C   copper-core center electrode (P is for platinum-core)
  X   1.1-mm (0.043") spark gap (missing letter means not pre-gapped)

Champion RC8YC4
  R   Resistor type
  C   14-mm thread, 5/8" hex shell, 3/4" reach
  8   Heat range (8 and 9 are medium, 10 is hotter, 7 is colder)
  Y   standard projected core nose
  C   copper-core center electrode
  4   wide spark gap required for Federal and California standards (missing number means not pre-gapped)

The stock spark plug for the turbocharged, DOHC, 6G72 engine is NGK PFR6J-11 or Denso PK20PR-P11, which have platinum-tipped electrodes. 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. NGK and Denso spark plugs are available online at the stores listed below.

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). The greenish colored areas in the table show the available replacements in the same heat range as the factory plugs. The reddish colored areas show one heat range hotter, and the bluish colored areas show one heat range colder. 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. 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. 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. 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.

A higher voltage spark can cause more-complete combustion and therefore increase cylinder pressure and produce more power. The electrode tip diameter is much smaller for platinum and iridium plugs, which requires less voltage than wider conventional plugs to generate a spark at a given gap. Consequently, the spark gap is widened for precious metal plugs to return the required voltage to conventional-plug levels. When switching from a platinum-tipped electrode spark plug to a conventional nickel-alloy electrode spark plug, the spark gap should be reduced from the typical platinum-plug gap of about 0.043" to the more typical conventional plug gap of 0.032" to 0.034", only if the ignition system cannot support the wider gap. I am presently (August 2003) using NGK BCPR6ES plugs at 0.040" gap with MSD 8.5mm Super Conductor ignition wires and new factory coils and power transistor without getting spark blowout at 15.5 psi boost to redline.

Spark Plug Cross Reference Guide for the Mitsubishi DOHC 6G72
NGK NGK
Heat
Range		 Resistor
Type		 NGK
Iridium IX		 Denso Denso
Iridium
Power		 Denso
Iridium
Tough		 AC Delco Bosch Champion
BCPR5ES
BCPR5ES-11		 5 Yes BCPR5EIX-11 Q16R-U
Q16R-U11		 IQ22 VQ22 CFR3CLS
-		 FR8DC
FR8DCX		 RC10YC
RC10YC4
BKR5ES
BKR5ES-11		 5 Yes BKR5EIX
BKR5EIX-11		 K16PR-U
K16PR-U11		 IK22 VK22 - FR8DPX*
PFR6J-11* 6 Yes BKR6EIX-11 PK20PR-P11* IK24 VK24 - FR7DPX*
FR6DPX*		 -
BCPR6ES
BCPR6ES-11		 6 Yes BCPR6EIX-11 Q20R-U
Q20R-U11		 IQ24 VQ24 CFR2CLS
-		 FR7DC,FR6DC
FR7DCX,FR6DCX		 RC9YC
RC8YC
RC9YC4
RC8YC4
BKR6ES
BKR6ES-11		 6 Yes BKR6EIX
BKR6EIX-11		 K20PR-U
K20PR-U11		 IK24 VK24 -
FR2LS		 FR7DP*,FR6DP*
FR7DPX*
FR6DPX*
BCPR7ES
BCPR7ES-11		 7 Yes - Q22PR-U
Q22PR-U11		 IQ27 VQ27 CFR1CLS
-		 FR5DC RC7YC
RC7YC4
BKR7ES-11 7 Yes - K22PR-U11 IK27 VK27 - FR5DP*
BCP6ES
BCP6ES-11		 6 No - Q20-U11 IQ24 VQ24 - F6DCX -
BCP7ES 7 No - Q22P-U IQ27 VQ27 - F5DC -
R5672A-8 8 No - - IQ29 - - - C63YC
R5672A-9 9 No - - IQ31 - - - C59YC
* Indicates platinum tips on electrodes (platinum core for Bosch).
- All listed plugs have a 14-mm thread diameter (1.25-mm pitch), 19-mm (3/4") reach, and 16-mm (5/8") hex size.
- NGK R5672A are a "V-power" projected tip type BK-ES plug with nickel alloy electrodes available in heat ranges 8, 9, and 10.
- Denso lists the following heat range equivalence with NGK: (NGK=Denso) 5=16, 6=20, 7=22, 8=24, 9=27. Nevertheless, many
   3S owners report that Denso heat range 24 acts similar to NGK heat range 6 in 3S cars and so that is presented above.
- Bosch Platinum 2-, 3-, and 4-electrode plugs are not listed because many owners report problems with these in our engines.
- Autolite offers the "52" replacement for the R5672A-8 and the "51" replacement for the R5672A-9.
- Motorcraft offers the "AGSP32C" replacement for the BCPR5ES-11 and the "AGPR12C" replacement for the BCPR7ES.
- Some Champion plug type=stock number: RC10YC4=346, RC9YC=344, RC9YC4=430, RC8YC4=345, RC7YC=340, C63YC=796, C59YC=792.
- Information taken from various sources on the internet.

Online Stores

http://www.clubplug.net/
http://www.sparkplugs.com/
http://www.jagworks.com/

Online References

http://www.clubplug.net
http://www.ngkspark.com.au/
http://home.att.net/~ngkaz/wsb/html/view.cgi-home.html-.html
http://home.att.net/~ngkaz/wsb/Master_Cross_Reference_Charts4.xls
http://home.att.net/~ngkaz/wsb/Racing_Plugs.xls
http://www.denso.co.jp/PLUG/cross_ref/index.html
http://www.users.globalnet.co.uk/~pbegley/crossref.htm
http://www.denso.co.jp/PLUG/iridium-e/q16.html
http://www.denso.co.jp/PLUG/iridium-e/q23.html
http://www.edelbrock.com/automotive/sparkplugs.html

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Except for the small gif and jpg images, the content, images, photographs, text, and multimedia displayed are Copyright ©2000-2006 by Jeff Lucius and K2 Software. All rights reserved. No part, section, image, photo, article, or whole of this site may be reposted or redisplayed without permission of the authors.
Page last updated January 25, 2006.