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Product details
EMPI 98-9963-B is an NGK BP5ES spark plug with a 14mm thread, 3/4 inch (19mm) reach and heat range 5, for cylinder heads that take 14mm long-reach plugs. EMPI sells it individually from boxes of four, with the terminal nut installed. It is a non-resistor plug with a gasket seat and comes gapped at 0.8mm (0.031 inch). In NGK's numbering, a lower heat range number is a hotter plug with a longer insulator nose, and a projected plug puts the spark farther into the chamber for better ignitability.
Choose by reach, then heat range. EMPI's 98-9964-B (NGK BP6ES) is the same plug one step colder, the 98-9957-B (NGK B5ES) is the related plug without the P in its code, and the 98-9965-B (NGK BP5HS) is the 1/2 inch reach version. NGK warns that a plug too cold for the engine builds deposits on the firing end, while one too hot can cause pre-ignition.
Technical Details
- Manufacturer: EMPI (NGK plug)
- Manufacturer part number: 98-9963-B
- NGK reference: BP5ES
- Thread: 14mm
- Reach: 3/4 inch (19mm)
- Heat range: 5
- Resistor: None
- Seat: Gasket
- Gap: 0.8mm (0.031 inch)
- Sold as: Each (4 per box)
Fitment & Compatibility
Fits heads tapped for 14mm, 3/4 inch reach plugs. EMPI's stock-replacement Type 1 dual port heads take 14mm 1/2 inch or 12mm 3/4 inch reach plugs, so this plug does not suit them.
Installation & Tuning Notes
Too much reach puts threads into the combustion chamber, and too little leaves exposed threads in the head that collect carbon. Set the gap to your engine's specification.
Common Questions
Is BP5ES hotter or colder than BP6ES?
Hotter. On NGK's scale a higher number is colder, so the BP6ES (EMPI 98-9964-B) is one step colder.
Do I get one plug or a box?
One plug per unit, so order four for a four-cylinder engine.
