what is the best temperature to run at to get the best performance?

 

there's a LOT of depends to that answer.

non-cc carb or EFI?

Reprogrammed ECM or stock?

If we're talking carbed engine with no computer,
then coolant temps around 160*F and oil temps around 250*F
usually give the best power on the dyno.
This also depends on if you set the engine clearances tight or loose. Looser engines like to run warmer.

If we're talking port injected EFI were you have reprogrammed the fuel & timing curve, then a coolant temp as low as possible gives the most power.

A stock port injected vehicle will not make it's best power with a very cold coolant temp unless you fool the ECM to think it's actually warmer.

Keep in mind that cooler oil temps will cost you power. Oil coolers are only helpful on severe heavy duty applications like towing or circle-track cars.

 

If you really want to get technical, the most powerful temp is the lowest you can go. On a Temperature vs. entropy graph of a four-cycle engine(Carnot cycle), the lower the incoming charge/engine temp- the higher the work output (horsepower)

 

Don't confuse incoming air temp with engine temp. If the engine is feed cold air, engine temp can be much higher to make max power. In most cars, lowering the engine temp helps power by lowering the incoming air temp. But only to a point. Running your engine at 0 degrees isn't going to make max power. A lot of factors affect the engine temp to make max power. Circle track cars (like Nascar), that run lots of rpm for extended periods of time make the best power at a warmer temp--around 200.

 

If you take into account the coefficient for expansion of the metals, and form a function of temp vs expansion; you will see as the metal contracts the compression goes down- which is the reason for running the 200 deg. Depending on your engine tolerancing and your rings, compression, all that then you can determine your optimum compression temp.