Spark Plugs for Speedway

Spark Plugs for Speedway

The selection of Spark Plugs for standard compression engines operating on Methanol at high temperatures in Wingless and high compression big cam in Street Stock on petrol requires some careful consideration.

If a standard heat range plug is used it would be expected that the operation would be too hot and failure of plug and piston would result.

Many spark plug brands these days make plugs that operate over a broad heat range.

NGK plugs are giving problems across all areas of speedway at the moment I would not recommend using them in a wheelbarrow

If you use the colder range plug you may foul the plug when the engine is cold from our experience it is rare that they will come good again and would recommend having a spare set.


  • Use Champion RS7YX4 or RS7YX6
  • Use Bosch HR7DCX
  • Gap all plugs in wingless at 0.040″  or 1.0mm (Methanol)


  • Use Bosch  HR7DCX
  • Use Champion RS7YX4 or RS7YX6
  • Gap at 0.050″  or 1.25mm  (Petrol)


  • Use Bosch  WR8DC (severe use)
  • Use Bosch  WR9DC (std Engine?)
  • Gap at 0.035″  or 0.90mm

For the Ford, if you use the std plug and then use it in a severe application you may damage it, if you use the severe use plug it may foul when cold, this is common problem if the fuel amount is not correct

BA and Bf Falcon

o   STD  Bosch FR7DC

o   Cold Bosch FR6DC

Gap at 0.035″  or 0.90mm