I have a 350 slightly modified in a 1970 Camaro. I have a Griffen aluminum radiator, 165 high flow thermostat, edelbrock waterpump, and black magic electric fan and an MSD 6AL Ignition system. Running initial advance at 8 degrees with maximum advance around 38-40. Problem is, when running down the road, this thing stays cool. When idling, the car gets hot. Hot enough to put coolant in the catch can. Thought this might be either a cracked head or bad head gasket, but don't seem to be loosing coolant, don't have any bubbles in the radiator, and no excessive moisture out the exhaust. Have tried a larger crankshaft pulley to spin the H2O pump faster, doesn't make a difference. Have also tried a flex fan and no changes. Carb is adjusted correctly so don't think this is a lean condition at idle. Plugs look good, slightly brown. Don't know what else to try. Any suggestions?