N11YC Champion plug is equivalent to an NGK BP5ES.
Many people here run this hotter plug, BP (or was it Bosch Australia?) recommended going 1 heat range hotter than original when running unleaded fuels, particularly in traffic.
I put BP5ES in my 1412 stroker (it was 10.5:1 C/R) and they are still going fine.
My 1360 (11.0:1) is running BPR6ES because I had a new set.
I would run yours, but keep an eye on the electrodes; if they blister the plug is perhaps too hot.

[edit] For track work though you would want a colder plug.
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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.
