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Butler Performance Inc. - Plugs for 72' and Later Cast Iron Heads
Here is an example if you have a question about the heat range on an NGK spark plug.
The lower the #, the hotter the plug is.
(Example- -6 is a hotter plug than -9)
Spark plug gap for Points is .035 and any electronic or MSD is .040-.045
General Guideline- Pump gas street engines would use a -5 to -7 heat range, high compression race engines may use a -8 or -9 heat range, and boosted/nitrous engines may use a -9 or -10 heat range depending on levels of boost/nitrous.
The lower the #, the hotter the plug is.
(Example- -6 is a hotter plug than -9)
Spark plug gap for Points is .035 and any electronic or MSD is .040-.045
General Guideline- Pump gas street engines would use a -5 to -7 heat range, high compression race engines may use a -8 or -9 heat range, and boosted/nitrous engines may use a -9 or -10 heat range depending on levels of boost/nitrous.
Browse Plugs for 72' and Later Cast Iron Heads Products
Items 1-7 of 7
Description: NGK-R5673-8 Spark Plug (72 & Later Cast Iron Heads) 5/8" Hex .460 Reach 14mm Taper Seat Recessed Tip (Set)
Item #: NGK-3249-8
Condition:
New
Price: $54.95
Description: NGK-R5673-9 Spark Plug (72 & Later Cast Iron Heads) 5/8"Hex .460 Reach 14mm Taper Seat Rec Tip Nitrous (Set)
Item #: NGK-3442-8
Condition:
New
Price: $54.95
Description: NGK-R5674-6 Spark Plug (72 & Later Cast Iron Heads) 5/8'Hex .460 Reach 14mm Taper Seat Ext Tip (Set)
Item #: NGK-4449-8
Condition:
New
Price: $54.95
Description: NGK-R5674-7 Spark Plug (72 & Later Cast Iron Heads) 5/8'Hex .460 Reach 14mm Taper Seat Ext Tip (Set)
Item #: NGK-5034-8
Condition:
New
Price: $54.95
Description: NGK-R5674-8 Spark Plug (72 & Later Cast Iron Heads) 5/8" Hex 14mm Taper Seat Ext Tip (Set)
Item #: NGK-5657-8
Condition:
New
Price: $54.95
Description: NGK-UR5 Spark Plug (72 & Later Cast Iron Heads) 5/8"Hex .460 Reach 14mm Taper Seat Ext Tip (Set)
Item #: NGK-2771-8
Condition:
New
Not Available
Price: $54.95
Description: NGK-YR-5 Spark Plug (72 & Later Cast Iron Heads) 5/8'Hex .460 Reach 14mm Taper Seat Recessed Tip (Set)
Item #: NGK-7052-8
Condition:
New
Price: $54.95
Items 1-7 of 7