Spark Plug Heat Range/Cross Reference Thread Size/Reach Hex Heat Range Autolite Champion E3
Standard Non-Resistor Spark Plugs
Power/Projected Tip Non-Resistor Spark Plugs
NGK
Accel
Autolite
Champion
E3
NGK
Chevrolet, Chrysler (Wedge), Oldsmobile, Pontiac - Standard Reach - Flat Seat with Gasket
Hot
— — — — — — — — — — — NGKB8S — — — — AUT353 CHPJ4C — NGKB7S AUTAR3935 CHPC63CX — NGKR5671A-7 AUTAR3934 CHPC61CX E3PE3.103 ‡ NGKR5671A-8 AUTAR3933 † CHPC59CX E3PE3.102 ‡ NGKR5671A-9 AUTAR3932 † CHPC57CX E3PE3.101 ‡ NGKR5671A-10 — — — — AUTAR2593 — — — AUTAR2592 — — — — — — — — — — — — — — — — — — —
— — — — NGKR5670-5
— AUTAR73 — AUTAR72
— — NGKR5670-6 — — NGKR5670-7
14mm/3/8" 13/16"
— — — — NGKR5670-8 — — — — NGKR5670-9
Cold
Chevrolet (Big Block), Chrysler (Hemi) - Flat Seat with Gasket
Hot
— — — — —
— AUTAR3911 CHPC61YC
— NGKR5672A-8
14mm/3/4" 5/8"
— AUTAR3910 †
CHPC59YC E3PE3.106 ‡ NGKR5672A-9
— — CHPC57YC
— NGKR5672A-10
Cold AUTAR3931 CHPC55CX — NGKR5671A-11
— — — — —
Chevrolet (Big Block), Chrysler (Hemi) - Flat Seat with Gasket
Hot
— — — — — — — — — —
— AUTAR53 — AUTAR52 — AUTAR51 — AUTAR50
— — — — — — — — — — — —
14mm/3/4" 13/16"
Cold
— — — — —
Chevrolet (Small Block), Ford (Small Block) - Conical/Tapered Seat
Hot
— — — — ACL0276S-4*
— — — —
— — — NGKR5673-6 AUTAR135 CHPV63C — NGKR5673-7
— — — — NGKR5674-6
— AUTAR13 — AUTAR12
— — NGKR5674-7
14mm/.460" 5/8"
AUTAR134
— E3PE3.105 ‡
—
— E3PE3.107 ‡
NGKR5674-8
AUTAR133 CHPV59C E3PE3.104 ‡
NGKR5673-8
— — — — NGKR5674-9 — — — — NGKR5674-10 — — — — —
AUTAR132 CHPV57C — NGKR5673-9 — — — NGKR5673-10 — — — — — — — — AUTAR474 CHPS59C — —
Cold
Chevrolet (Big Block), Ford - Conical/Tapered Seat
Hot
— — CHPRS9YC
— —
— AUTAR94
— — NGKR5724-8
14mm/.708" 5/8"
— AUTAR93 CHPS59YC E3PE3.109 ‡
NGKR5724-9
AUTAR473 CHPS57C E3PE3.108 ‡
—
— AUTAR92
— — NGKR5724-10
Cold AUTAR472 CHPS55C — —
— — — — —
Ford (Windsor and Big Block) - Conical/Tapered Seat
Hot
— — — — — — — — — — — —
— AUTAR33 — AUTAR32
— — — — — NGKAP8FS
18mm/.460" 13/16"
Cold — — — — — Important Note: Use cross reference chart as a guide only. Due to differences in design and material, plugs listed in cross reference are not exactly alike. * “Shorty“ spark plug for added header clearance, sold in 4-pack. ‡ E3 DiamondFIRE fixed gap spark plugs cannot be adjusted. † Special Autolite Racing "X" style electrode spark plug that alleviates piston/spark plug clearance issues is also available; simply add “X” to end of part number.
TECH TIP
Spark Plug Diagnosis
Pictures Courtesy of Autolite
• Determine the thread diameter, length (reach), and whether tapered or gasket (flat) seat. • Select gap style. • Select heat range. • Adjust fuel mixture and spark advance timing for maximum performance. • Inspect plugs and pistons for evidence of detonation, abnormal combustion, or excessive temperatures. • Stay with the same plug type after final heat range selection unless major modifications have been made (increasing the horsepower or operating range). Normal Fuel Fouled Detonation
Oil Fouled
Spark Plug Heat Range Tech $VSDUNSOXJ¶V+HDW5DQJHGH¿QHGDVWKHPHDVXUHRIKRZIDVWWKHWLSRIWKHSOXJGLVVLSDWHVFRPEXVWLRQKHDWFDQUDQJHIURPDV ORZDV)WRDVKLJKDV)0DQXIDFWXUHUVRIIHUSOXJVLQPDQ\KHDWUDQJHVIURPFROGWKURXJKPHGLXPKRWWRYHU\KRW,W is imperative that the plug stay cool enough to prevent pre-ignition or electrode destruction, and still remain hot enough to burn off FRPEXVWLRQGHSRVLWVWKDWIRUPDWWKH¿ULQJWLS$SOXJWKDWLVH[FHVVLYHO\FROGRUKRWIRUWKHDSSOLFDWLRQLQTXHVWLRQZLOOHYHQWXDOO\ FDXVHWKHHQJLQHWRPLV¿UH:KHQZRUNLQJZLWKDQHQJLQHWKDWLVVWRFNRUPLOGO\PRGL¿HGLWLVRIWHQEHVWWRXVHWKHSOXJUHFRPPHQG - ed by the car manufacturer. However, if the compression ratio has been altered, a different heat range plug may be required. Many racers rely upon their engine builder for plug heat range recommendations. If a racer is unsure of the correct heat range to use, it LVDOZD\VUHFRPPHQGHGWR³VWD\RQWKHVDIHVLGH´DQGXVHDFROGHUSOXJ$VZLWFKLQKHDWUDQJHFDQFKDQJHWKHWHPSHUDWXUHRIWKH VSDUNSOXJWLSE\),IWKHSOXJVHOHFWHGLVWRRFROGLWZLOOHYHQWXDOO\IRXODQGPLV¿UHEXWLWZLOOQRWGDPDJHWKHHQJLQH$SOXJ which is too hot can cause pre-ignition and detonation, often resulting in a severely damaged engine.
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CIRCLE TRACK 2021-22
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