[BOBOCobra]

Ran out of space but do the simple things before you start running lines from the back of the heads, etc... Again, you need air and water flow, and the reason you are getting hot is you are lacking on both. Key point you made is that it cools at 2500 rpm idle, you are simply moving more water so you need to do that at idle by spinning the pump faster and having a high flow pump without idle speed of 2500. I idle at 950, pump is almost 1200. The only way to dissipate the heat is move air through the rad fins. There is no such thing as too much. Pull through more air with shrouds and high CFM fans. My fans are as close to the rad as I can get and tilt slightly down to push the hot air down the tunnel. I use a 12# cap and spit about a pint into the overflow on a hot day. 521CID, 580 HP....I generate a LOT of heat