160-degree thermostat too cold?

MOPARoldtimer said

My 408 has a 10.5:1 C.R. with ported "J" heads and has been detonating pretty badly on 91 octane, so I thought I'd try a cooler thermostat. I bought a 160-degree t-stat, and when I removed the old one I noticed that the engine builder had installed a 195-degree unit. What will be the effect of installing the 160-degree unit? Is it too cold? If so, what is the minimum temperature t-state you would consider using?

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A cooler thermostat may only mask an underlying overheating problem, and may lead to less efficient combustion as too much energy is being expelled via the radiator rather than the rear wheels. The purpose of an internal combustion engine, after all, is to turn heat into motion.

I had a similar problem with my slant-6 (compression 10.3:1) but found a solution in an aluminium radiator, engine-oil radiator and, most of all, a distributor from Hemi Performance (Australia) with an optimal ignition curve. The fact that I have easy access to 100 octane petrol from just across the border also helps. Now I have no pre-ignition, the engine runs cooler and the fuel economy is slightly better as well ; a consideration when a liter of 100 cost 203 centimes (about $ 8.50 a US gallon).