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Butler Performance Inc. - Plugs for 71' and Earlier 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 71' and Earlier Cast Iron Heads Products
Items 1-5 of 5
Description: NGK-B8S Spark Plug (71 & Earlier Cast Iron Heads) 13/16"Hex 3/8" Reach 14mm Gasket Seat Recessed Tip (Set)
Item #: NGK-3810-8
Condition:
New
Price: $24.95
Description: NGK-R5670-6 Spark Plug (71 & Earlier Cast Iron Heads) 13/16"Hex 14mm Gasket Seat 3/8 Reach Ext. tip (Set)
Item #: NGK-2746-8
Condition:
New
Price: $24.95
Description: NGK-R5670-7 Spark Plug (71 & Earlier Cast Iron Heads) 13/16"Hex 14mm Gasket Seat 3/8 Reach Ext Tip (Set)
Item #: NGK-2891-8
Condition:
New
Price: $24.95
Description: NGK-R5670-8 Spark Plug (71 & Earlier Cast Iron Heads)13/16" Hex 3/8 Reach 14mm Gasket Seat Ext Tip (Set)
Item #: NGK-3354-8
Condition:
New
Price: $24.95
Description: NGK-R5670-9 Spark Plug (71 & Earlier Cast Iron Heads)13/16 Hex 3/8" Reach 14mm Gasket Seat Ext Tip Nitrous (Set)
Item #: NGK-3913-8
Condition:
New
Price: $24.95
Items 1-5 of 5