Decent grade 7 spark plugs cant find a definitive answer with the search

[TubbyTwo]

from NGK.com FAQ:

After you have identified the numbering system for your plug, merely raise or lower that number to change the heat range.

REMEMBER, NGK PLUGS GET COLDER THE HIGHER THE NUMBER, HOTTER THE LOWER THE NUMBER.
Heat ranges are not the same between brands.

Say you are starting with a BKR6E-11
if you want a colder plug, you would use BKR7E-11
if you want a hotter plug, you would use BKR5E-11
(again, on non-racing plugs, the number after the "-" refers to the gap)

 

[PhilW]

I use sparkplugs.co.uk

The -11 are the wrong gaps iirc.

Standard gaps are fine on the BKR7E.

 

[TubbyTwo]

bit more info:

The spark plug can help maintain the optimum combustion chamber temperature. The primary method used to do this is by altering the internal length of the core nose, in addition, the alloy compositions in the electrodes can be changed. This means you may not be able to visually tell a difference between heat ranges. When a spark plug is referred to as a “cold plug”, it is one that transfers heat rapidly from the firing tip into the engine head, which keeps the firing tip cooler. A “hot plug” has a much slower rate of heat transfer, which keeps the firing tip hotter.

An unaltered engine will run within the optimum operating range straight from the manufacturer, but if you make modifications such as a turbo, supercharger, increase compression, timing changes, use of alternate racing fuels, or sustained use of nitrous oxide, these can alter the plug tip temperature and may necessitate a colder plug. A rule of thumb is, one heat range colder per modification or one heat range colder for every 75–100hp you increase. In identical spark plug types, the difference from one full heat range to the next is the ability to remove 70°C to 100°C from the combustion chamber.

The heat range numbers used by spark plug manufacturers are not universal, by that we mean, a 10 heat range in Champion is not the same as a 10 heat range in NGK nor the same in Autolite. Some manufacturers numbering systems are opposite the other, for domestic manufacturers (Champion, Autolite, Splitfire), the higher the number, the hotter the plug. For Japanese manufacturers (NGK, Denso), the higher the number, the colder the plug.

 

[vwbassett]

Interesting stuff, but at 75-100bhp thats quite a margin so would i be right in saying thats starting at the high stage 2 power onwards?