HarrisSpeedWorks

Hey guys, been working on this for a little while and finally have it ready to post. Maybe someone can sticky it to the top so that people can easily reference it? It's fairly hard to compare each manufacturers heat range since there are so many factors involved but this is, in my opinion, the closest match for NGK's heat range system, which was used in the chart. If you guys would like to see certain plug manufacturers added, let me know.



Spark Plug Info

**Note: Heat ranges are determined by NGK standards. Not all plug manufacturers follow the same guidelines.

***Note: List is intended for reference only. Please consult with head mfg. and ignition mfg. for proper gap.

****Note: NGK IX and Denso plugs are Iridium.

LT1
Thread – 14mm
Reach - .708”
Socket – 5/8 hex
Seat - Taper
Stock Heat Range: 5
Gap: .050
Plug: NGK TR55 (stock number 3951); NGK TR55IX (stock number 7164); Autolite 764; Champion RS14YC6 (stock number 13); Denso IT-16 (stock number 5325)

Nitrous (one step colder)
Heat range: 6
Gap: .035 - .038
Plug: NGK TR6 (stock number 4177); NGK TR6IX (stock number 3689); Autolite 103; Denso IT-20 (stock number 5326)

Nitrous (two steps colder)
Heat Range: 7
Gap: Consult
Plug: NGK BR7EF (stock number 3346); NGK TR7IX (stock number 3690); Autolite AR94; Denso IT22 (stock number 5327)


LT1 w/ AFR heads
Thread – 14mm
Reach – 3/4”
Socket – 5/8 hex
Seat – Gasket
Stock – MFG Recommendations
Heat Range: 9
Gap: Consult ignition mfg.
Plug: NGK 5672A-9 (stock number 7405); Autolite AR3910; Champion C59YC (stock number 792); Denso IQ27 (stock number 5315); Denso IQ01-27 (stock number 5708)(diagonal platinum ground); Denso IQ02-27 (stock number 5711)(horizontal platinum ground)

Nitrous (one step colder)
Heat Range: 10
Gap: Consult ignition mfg.
Plug: NGK 5672A-10 (stock number 7942); Autolite AR50; Denso IQ31 (stock number 5323)

Nitrous (two steps colder)
Heat Range: 11
Gap: Consult ignition mfg.
Plug: Denso IQ34 (stock number 5324)


LT1 w/ Trick Flow & Edelbrock Heads
Thread – 14mm
Reach – 3/4”
Socket – 5/8 hex
Seat – Gasket

Stock – MFG Recommendations: approx under 9:1 compression
Heat Range: 4
Gap: Consult ignition mfg.
Plug: NGK FR4 (stock number 5155); NGK BKR5EIX (stock number 6341); Autolite 3926; Champion RC12YC (stock number 71); Denso IK16 (stock number 5303)

MFG Recommendations: approx 10.5:1 compression
Heat Range: 5
Gap: Consult ignition mfg.
Plug: NGK FR5 (stock number 7373); Autolite AR3924 (Racing Plug); Autolite 3924; Champion RC9YC (stock number 2075); Denso K20PR-U (stock number 3145); Denso IK20 (stock number 5304)

MFG Recommendations: approx 11:1 compression
Heat Range: 8
Gap: Consult ignition mfg.
Plug: NGK R5672A-8 (stock number 7173); Autolite AR3911; Champion C63YC (stock number 796); Denso IQ24 (stock number 5314)

MFG Recommendations: approx 12:1 compression
Heat Range: 9
Gap: Consult ignition mfg.
Plug: NGK R5672A-9 (stock number 7405); Autolite AR3910; Champion C61YC (stock number 785); Denso IQ27 (stock number 5315)

MFG Recommendations: approx 13:1 compression
Heat Range: 9 - 10
Gap: Consult ignition mfg.
Plug: NGK R5671A-9 (stock number 5238); Autolite AR3933; Champion C59CX (stock number 296); Denso IK27 (stock number 5312)

MFG Recommendations: approx 14:1 compression
Heat Range: 10
Gap: Consult ignition mfg.
Plug: NGK R5671A-10 (stock number 5820); Autolite AR3932; Champion C57CX (stock number 295); Denso IK-31 (stock number 5321)

**NOTE: Use chart for static compression and adjust heat range for nitrous use accordingly.



LS1 Stock and AFR
Thread – 14mm
Reach - .708”
Socket – 5/8 hex
Seat - Taper
Stock Heat Range: 5
Gap: .060
Plug: NGK TR55 (stock number 3951); NGK TR55IX (stock number 7164); Autolite 764; Denso IT-16 (stock number 5325)

Nitrous (one step colder)
Heat Range: 6
Gap: .035 - .038
Plug: NGK TR6 (stock number 4177); NGK TR6IX (stock number 3689); Autolite 103; Denso IT-20 (stock number 5326)

Nitrous (two steps colder)
Heat Range: 7
Gap: Consult
Plug: NGK BR7EF (stock number 3346); NGK TR7IX (stock number 3690); Autolite AR94; Denso IT22 (stock number 5327)

Nitrous (two and a half steps colder)
Heat Range: 8
Gap: Consult
Plug: NGK R5724-8 (stock number 7317); NGK TR8IX (part number 3691); Denso IT-24 (stock number 5328)

Nitrous (three steps colder)
Heat Range: 9
Gap: Consult
Plug: NGK R5724-9 (stock number 7891); Autolite AR93; Denso IT-27

Nitrous (four steps colder)
Heat Range: 10
Gap: Consult
Plug: NGK R5724-10 (stock number 7993); Autolite AR92


LS1 w/ Edelbrock and Dart Heads
Thread – 14mm
Reach – 3/4”
Socket – 5/8 hex
Seat – Gasket

Stock – MFG Recommendations: approx under 9:1 compression
Heat Range: 4
Gap: Consult ignition mfg.
Plug: NGK FR4 (stock number 5155); NGK BKR5EIX (stock number 6341); Autolite 3926; Champion RC12YC (stock number 71); Denso IK16 (stock number 5303)

MFG Recommendations: approx 10.5:1 compression
Heat Range: 5
Gap: Consult ignition mfg.
Plug: NGK FR5 (stock number 7373); Autolite AR3924 (Racing Plug); Autolite 3924; Champion RC9YC (stock number 2075); Denso K20PR-U (stock number 3145); Denso IK20 (stock number 5304)

MFG Recommendations: approx 11:1 compression
Heat Range: 8
Gap: Consult ignition mfg.
Plug: NGK R5672A-8 (stock number 7173); Autolite AR3911; Champion C63YC (stock number 796); Denso IQ24 (stock number 5314)

MFG Recommendations: approx 12:1 compression
Heat Range: 9
Gap: Consult ignition mfg.
Plug: NGK R5672A-9 (stock number 7405); Autolite AR3910; Champion C61YC (stock number 785); Denso IQ27 (stock number 5315)

MFG Recommendations: approx 13:1 compression
Heat Range: 9 - 10
Gap: Consult ignition mfg.
Plug: NGK R5671A-9 (stock number 5238); Autolite AR3933; Champion C59CX (stock number 296); Denso IK27 (stock number 5312)

MFG Recommendations: approx 14:1 compression
Heat Range: 10
Gap: Consult ignition mfg.
Plug: NGK R5671A-10 (stock number 5820); Autolite AR3932; Champion C57CX (stock number 295); Denso IK-31 (stock number 5321)

**NOTE: Use chart for static compression and adjust heat range for nitrous use accordingly.



4.6 Mustang GT
Thread – 14mm
Reach - .708”
Socket – 5/8 hex
Seat - Taper
Stock Heat Range: 5
Gap: .054
Plug: NGK TR55 (stock number 3951); NGK TR55IX (stock number 7164); Motorcraft AWSF-32C (copper); Autolite 764; Denso IT-16 (stock number 5325)

Nitrous (one step colder)
Heat Range: 6
Gap: .035 - .038
Plug: NGK TR6 (stock number 4177); NGK TR6IX (stock number 3689); Motorcraft AWSF-22C (copper); Autolite 103; Denso IT-20 (stock number 5326)

Nitrous (two steps colder)
Heat Range: 7
Gap: Consult
Plug: NGK BR7EF (stock number 3346); NGK TR7IX (stock number 3690); Motorcraft AWSFA-12C (copper); Autolite AR94; Denso IT-22 (stock number 5327)

Nitrous (two and a half steps colder)
Heat Range: 8
Gap: Consult
Plug: NGK R5724-8 (stock number 7317); NGK TR8IX (part number 3691); Denso IT-24 (stock number 5328)

Nitrous (three steps colder)
Heat Range: 9
Gap: Consult
Plug: NGK R5724-9 (stock number 7891); Autolite AR93; Denso IT-27

Nitrous (four steps colder)
Heat Range: 10
Gap: Consult
Plug: NGK R5724-10 (stock number 7993); Autolite AR92



4.6 Mustang Cobra (96-01)
Thread – 14mm
Reach - .708”
Socket – 5/8 hex
Seat - Taper
Stock Heat Range: 5
Gap: .054
Plug: NGK TR55 (stock number 3951); NGK TR55IX (stock number 7164); Autolite 764; Denso IT-16 (stock number 5325)

Nitrous (one step colder)
Heat Range: 6
Gap: .035 - .038
Plug: NGK TR6 (stock number 4177); NGK TR6IX (stock number 3689); Motorcraft AWSF-22C (copper); Autolite 103; Denso IT-20 (stock number 5326)

Nitrous (two steps colder)
Heat Range: 7
Gap: Consult
Plug: NGK BR7EF (stock number 3346); NGK TR7IX (stock number 3690); Motorcraft AWSFA-12C (copper); Autolite AR94; Denso IT22 (stock number 5327)

Nitrous (two and a half steps colder)
Heat Range: 8
Gap: Consult
Plug: NGK R5724-8 (stock number 7317); NGK TR8IX (part number 3691); Denso IT-24 (stock number 5328)

Nitrous (three steps colder)
Heat Range: 9
Gap: Consult
Plug: NGK R5724-9 (stock number 7891); Autolite AR93; Denso IT-27

Nitrous (four steps colder)
Heat Range: 10
Gap: Consult
Plug: NGK R5724-10 (stock number 7993); Autolite AR92



4.6 Mustang Cobra (03-04)
Thread – 14mm
Reach - .708”
Socket – 5/8 hex
Seat - Taper
Stock Heat Range: 6
Gap: .049 - .052 (have had better results with tighter gap)
Plug: NGK TR6 (stock number 4177); NGK TR6IX (stock number 3689); Motorcraft AWSF-22C (copper); Autolite 103; Denso IT-20 (stock number 5326)

Nitrous (one step colder)
Heat Range: 7
Gap: .035 - .038
Plug: NGK BR7EF (stock number 3346); NGK TR7IX (stock number 3690); Motorcraft AWSFA-12C (copper); Autolite AR94; Denso IT-22 (stock number 5327)

Nitrous (two steps colder)
Heat Range: 8
Gap: Consult
Plug: NGK R5724-8 (stock number 7317); NGK TR8IX (stock number 3691); Denso IT-24 (stock number 5328)

HarrisSpeedWorks

5.0 Mustang 87-95
Thread – 14mm
Reach - .460”
Socket – 5/8 hex
Seat – Taper
Stock Heat Range: 4
Gap: .054
Plug: NGK UR45 (stock number 6945); NGK UR45IX (stock number 3207)

Nitrous (one step colder)
Heat Range: 5
Gap: .035 - .038
Plug: NGK UR5 (stock number 2771); NGK UR5IX (stock number 7177)

Nitrous (two steps colder)
Heat Range: 6
Gap: Consult
Plug: NGK UR6 (stock number 7773); NGK UR6IX (stock number 7348)



5.0 Mustang Cobra 93-95 w/ GT-40 Heads
Thread – 14mm
Reach - .708”
Socket – 5/8 hex
Seat - Taper
Stock Heat Range: 5
Gap: .054
Plug: NGK TR55 (stock number 3951); NGK TR55IX (stock number 7164); Autolite 764 or 104; Denso IT-16 (stock number 5325)

Nitrous (one step colder)
Heat Range: 6
Gap: .035 - .038
Plug: NGK TR6 (stock number 4177); NGK TR6IX (stock number 3689); Motorcraft AWSF-22C (copper); Autolite 103; Denso IT-20 (stock number 5326)

Nitrous (two steps colder)
Heat Range: 7
Gap: Consult
Plug: NGK BR7EF (stock number 3346); NGK TR7IX (stock number 3690); Motorcraft AWSFA-12C (copper); Autolite AR94; Denso IT-22 (stock number 5327)

Nitrous (three steps colder)
Heat Range: 8
Gap: Consult
Plug: NGK R5724-8 (stock number 7317); NGK TR8IX (stock number 3691); Denso IT-24 (stock number 5328)



Ford F-150 Lightning (99-04)
Thread – 14mm
Reach - .708”
Socket – 5/8 hex
Seat - Taper
Stock Heat Range: 6
Gap: .049 - .052
Plug: NGK TR6 (stock number 4177); NGK TR6IX (stock number 3689); Motorcraft AWSF-22C (copper); Autolite 103; Denso IT-20 (stock number 5326)

Nitrous (one step colder)
Heat Range: 7
Gap: .035 - .038
Plug: NGK BR7EF (stock number 3346); NGK TR7IX (stock number 3690); Motorcraft AWSFA-12C (copper); Autolite AR94; Denso IT-22 (stock number 5327)

Nitrous (two steps colder)
Heat Range: 8
Gap: .033 - .036
Plug: NGK R5724-8 (stock number 7317); NGK TR8IX (stock number 3691); Denso IT-24 (stock number 5328)

Nitrous (three steps colder)
Heat Range: 9
Gap: Consult
Plug: NGK R5724-9 (stock number 7891); Autolite AR93; Denso IT-27 (stock number 5329)

johnny3986

I wish I was a genius...very nice!!

LameRandomName

Thank You!

BlownF1

Very nice! Thanks!!!

OBE1 95Z28

For the LT1 with stock style heads, it's my understanding that one heat range colder than stock is an Autolite 104, and an Autolite 103 is 2 heat ranges colder.

GetaZforgetGT

Nice....and anyone should be able to search and get a hit on it with a title like that.

Cmr0z28

Cool, thanks!

I thought the Autolite 104s are a step colder?

HarrisSpeedWorks

This is where the difficulty lies...none of the manufacturers are consistent with heat ranges and it is difficult to make a chart to reference the plugs. I personally consider the 104 to be 1/2 cold to the TR55's. Rather than throw that in the 1 whole step colder range, I put the 103's which are almost 1.5 colder range than the 55's. On small shots the 104's would suffice, but I personally would elect to install a set of 103's. Both Denso and NGK cross reference the 103 to the IT-20 and TR6. Hope that clears things up a little.

chevy94c

Awesome

Joe B

According to autolite a couple years ago, when they responded by e-mail to my plug heatrange question...they said that the autolite 104's are two solid heatranges colder than the factory stock heatrange plug (which is their autolite 106)......and that 103's would be 3 steps colder than stock........but who knows, I would never trust their hair brain employees

Injuneer

I've always assumed that the Autolite 104 is one step colder than the stock LT1 plug (I run 104's NA in the stroker), and the 103 was two steps colder (run that with a 125-150 shot of nitrous).

Cmr0z28

Yeah...I'm running the 104s spraying a 150 shot without any problems.

HarrisSpeedWorks

104 is half colder than stock. Rather than put that in the list as a full range colder and have someone experience detonation and blame the list, I felt it was "safer" to put the colder plug in. Autolites numbering system are complete opposite of NGK. The higher the last digit, the hotter the plug is. Meaning a 104 is hotter than a 103, where as NGK does the opposite, a 5 is hotter than a 6. Broken down, the first number in an autolite plug is its division (reach, thread, hex). Second number indicates resistor/non-resistor (even/odd respectively). Third number indicates heat range. If you guys would like to add a half cold or something of that nature to the list let me know or maybe a moderator could do it and we could throw the 104's in there and move the 103's to a 1 and a half? Sorry for all of the confusion guys, but its really difficult to throw all of the plugs into catagories such as this when there really isn't any standards for heat ranges.

Nick

gex598

I always thought that the TR55 were colder then stock plugs! I been spraying a 250 for 6 months now with no ill affect yet, I think I'll change to the TR6 before the next race. I did try the 103's and they fouled out from daily driving think the TR6's will also?