NGK R5671a-8

[QuickDart360]

Read up about non projected spark plugs. Ngk R5671a-8 are a race plug that is non projected and seems to have good reviews by some members here. My question is will these be a good choice for my 360? It is wild but mild mill. 340 X-heads, KB107 flat top pistons, 292 purple cam, Victor 340 intake, 9.5" FTI 3400-3600 stall converter and 3.91's out back. This in a dart sport. Have been running rn12yc and after it is fully warm it tends to ping/detonate some when getting heavy with the left foot.

 

[toolmanmike]

You didn't mention your initial timing or your curve or total. That can cause ping more than a spark plug. Those NGK's probably won't help a bit.

 

[Rat Bastid]

That 8 is waaaaaaaaaaaaay too cold for your application. I doubt that 12 Champion is too hot.

Like TMM said above, your timing curve is probably a bit off.

 

[Jeremiah (jd)]

-8 heat range is what I use for a 300 shot of nitrous. As said above; too cold.

NGK heat range scale is oppoaite of Champion and Autolite. A typical pump gas streeter uses a 4 or 5 heat range plug. If it was mine and the compression was marginal for pump 91 I would start with a NGK projected tip in the -6 range. If you need a pn let us know.

As a point of reference, stock NGK heat range is 5, projected tip.

I run a 7 non projected tip on a 175hp shot of nitrous and 28-29 deg total advance

I have had faulty Autolites and Champion plugs OOTB. So far I have yet to see a NGK plug DOA.

 

[AJ/FormS]

The RN12YC's are the right plug.
If you haven't milled the heck off your heads or decks
those non-quench chambers are huge for that cam, and need all the help they can get. The projected tip is your second move against detonation; Controlling the chamber temp being first.

 

[Bewy]

NGK, 5 heat range, & projected tip plugs are the place to start. Ignition curve, as others have suggested.

The enemy of det is heat. Make sure your engine runs as cool as possible. The temp on your gauge tells you what the temp is at the sender, not near the exh valves where the coolant might be experiencing localised boiling. Cold air induction can also help, as well as increasing HP.