Originally posted by musturbo
to all you guys with predators getting detonation= if you have added blower pulleys please go 2 ranges colder with your plugs! a 180 t-stat wouldn't hurt either.
Nothing against you, sir, and please don't take this negatively, but this above is not good advice.

The factory thermostat in these Lightnings and Harleys is already a 180. No need to change it, period, not even to a colder one. These rogue companies offering free 160 or *180* thermostats are just giving gimmicks to create additional sales. If one does happen to go colder, then I definitely do not suggest going less than a 170 stat.

Also, the pcm can actually add in more timing if your ECT and ACT temps are cooler, and this is not always desirable.

As for the plugs, if timing is too aggressive in a tune, regardless of whatever tuning device is used, colder plugs is NOT going to cure detonation or pinging, nor fix the aggressive issue of the tune.

If you're running factory boost, or up to around +4 #'s over stock, then I suggest a plug that is 1 step cooler. If you're running +4 and above, then I suggest 2 steps cooler on the plugs. The Denso IT20 is great for stock applications, and the IT22 for moderate to heavily modified Lightnings/Harleys (even Cobras).

I hope this helps.

Sincerely...