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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, Heat Range 8 (Set)
Item #: NGK-3810-8
Condition:
New
Price: $54.95
Description: NGK-R5670-6 Spark Plug (71 & Earlier Cast Iron Heads), 13/16" Hex, 14mm Gasket Seat, 3/8 Reach Ext. tip, Heat Range 6 (Set)
Item #: NGK-2746-8
Condition:
New
Price: $54.95
Description: NGK-R5670-7 Spark Plug (71 & Earlier Cast Iron Heads), 13/16" Hex, 14mm Gasket Seat, 3/8 Reach, Ext Tip, Heat Range 7 (Set)
Item #: NGK-2891-8
Condition:
New
Price: $54.95
Description: NGK-R5670-8 Spark Plug (71 & Earlier Cast Iron Heads), 13/16" Hex, 3/8 Reach, 14mm Gasket Seat, Ext Tip, Heat Range 8 (Set)
Item #: NGK-3354-8
Condition:
New
Price: $54.95
Description: NGK-R5670-9 Spark Plug (71 & Earlier Cast Iron Heads), 13/16" Hex, 3/8" Reach, 14mm Gasket Seat, Ext Tip, Nitrous, Heat Range 9 (Set)
Item #: NGK-3913-8
Condition:
New
Price: $54.95
Items 1-5 of 5