Mustang Spark Plug Choices Options

[Death Dealer]

5.0
Stock E7 heads:
AUTOLITE
stock--stock 25 (5) [14m, .460 Reach, 5/8" Hex]
1 step colder--24 (4) [14m, .460 Reach, 5/8" Hex]
2 step colder--23 (3) [14m, .460 Reach, 5/8" Hex]
-----AR133 (3) [*recessed tip, racing plug]
-----AR132 (2) [*recessed tip, racing plug]
-----AR131 (1) [*recessed tip, racing plug]

NGK
stock--(UR45) 6945 (Heat Range - 4) [14m, .460 Reach, 5/8" Hex]
1 step colder--(UR55) 2248 (5) [14m, .460 Reach, 5/8" Hex]
2 step colder--(UR6) 7773 (6) [14m, .460 Reach, 5/8" Hex]
-----(R5673-8) 3249 (8) [*recessed tip, racing plug]
-----(R5673-9) 3442 (9) [*recessed tip, racing plug]
-----(R5673-10) 4050 (10) [*recessed tip, racing plug]


GT40 Heads:
AUTOLITE
stock--765 (Heat Range - 5) [14mm, .708 Reach, 5/8" Hex]
1 step colder--764 (4) or 104 (4) [14mm, .708 Reach, 5/8" Hex]**
2 step colder--103 (3) [14mm, .708 Reach, 5/8" Hex]**
-----AR473 (3) [*recessed tip, racing plug]
-----AR472 (2) [*recessed tip, racing plug]

**The difference between the 764 plug and the 104/103 plug is the thread. The 764 plug is a half thread whereas the 104/103 plug is a full thread. The full thread plugs are duplicates of the half thread plugs in every other aspect, they both protrude the same amount into the combustion chamber.

NGK
stock--(TR4) 3754 (Heat Range - 4) [14mm, .708 Reach, 5/8" Hex]
1 step colder--(TR55) 3951 (5) [14mm, .708 Reach, 5/8" Hex]
2 step colder--(TR6) 4177 (6) [14mm, .708 Reach, 5/8" Hex]
-----(B8EFS) 1049 (8) [*recessed tip, racing plug]
-----(B9EFS) 1085 (9) [*recessed tip, racing plug]

TFS, Edelbrock, and AFR Heads:
[14mm, 3/4" Reach, 5/8" Hex, gasket seat]
AUTOLITE
1 step colder--3924 (4) [*recommended starting point]
2 step colder--3923 (3)
-----AR3933 (3) [*recessed tip, racing plug]
-----AR3932 (2) [*recessed tip, racing plug]
-----AR3931 (1) [*recessed tip, racing plug]

NGK
1 step colder--(FR5) 3686 (5) [*recommended starting point]
2 step colder--(BKR6EY) 3696 (6)
-----(R5671A-8) 4554 (8) [*recessed tip, racing plug]
-----(R5671A-9) 5238 (9) [*recessed tip, racing plug]
-----(R5671A-10) 5820 (10) [*recessed tip, racing plug]

MOTORCRAFT
1 step colder--AWSF22C
2 step colder--AWSF32C



4.6
MOTORCRAFT
stock--AWSF-32C (copper)
1 step colder--AWSF-22C (copper)
2 step colder--AWSFA-12C (copper)
AGSF-32C--FRPP heads

NGK
stock--TR-55/ 3951
1 step colder--TR-6 4177
1 step colder--NGK TR6
1 step colder--NGK BR6EF (Non-projected, resistor, v-groove copper)
2 step colder--NGK BR7EF (Non-projected, resistor, v-groove copper)
2 step colder--BP7EFS [PN - 3526] BR7EF [PN - 3346]
2.5 step colder--R5724-8 [PN - 7317]
3 step colder--R5724-9 [PN - 7891]
4 step colder--R5724-10 [PN - 7993]

AUTOLITE
stock--764
1 step colder--103
2 step colder--AR94
3 step colder--AR93
4 step colder--AR92

CHAMPION
YS-59C

DENSO
stock--IT16
1 step colder--IT20
2 step colder--IT22
3 step colder--IT24


Here is a list I have put together on the E7 and GT40 head.

NGK plugs are reverse of what Autolite plugs are in heat range numbering. Where the Autolite number drops indicating a colder plug, the NGK plug number goes up indicating a colder plug. Also, the NGK plug starting with the letter "R" and the Autolite plug starting with the letters "AR" are racing plugs. Let me begin.

14m, .460 Reach, 5/8" Hex, Tapered Seat (E7 head)
...Autolite...................................NGK
stock 25 (Heat Range - 5).......(UR45) 6945 (Heat Range - 4)
colder 24 (4).........................(UR55) 2248 (5)
colder 23 (3).........................(UR6) 7773 (6)
*recessed tip, racing plugs
......AR133 (3).........................(R5673-8) 3249 (8)
......AR132 (2).........................(R5673-9) 3442 (9)
......AR131 (1).........................(R5673-10) 4050 (10)

14mm, .708 Reach, 5/8" Hex, Tapered Seat (GT40 head)
...Autolite...................................NGK
stock 765 (Heat Range - 5).......(TR4) 3754 (Heat Range - 4)
colder 764 or 104 (4).............(TR55) 3951 (5)
colder 103(3).........................(TR6) 4177 (6)
*recessed tip, racing plugs
......AR473 (3).........................(B8EFS) 1049 (8)
......AR472 (2).........................(B9EFS) 1085 (9)