I have BBC 454 0.30 over, 10:1. In a 1984 El Cabellero. Runs perfect, makes decent power throughout my RPM range. Here is the problem, cannot keep it cool in traffic. Have high flow water pump, Griffen aluminum radiator, high flow thermostat, 7 blade flex fan appropriate distance from radiator with a full plastic GM shroud. @ 55 MPH runs between 180-190. Get into a stop and go situation and its all over. It gets to 230 in a hurry, so either I have to get going or shut it down. I am not convinced that timing is the issue. I am having trouble remembering whether I set the cam @ 4 or 6 degrees BTDC. (It has been a few years and car set idle for a while). It has been advanced that water may be cycling to fast through the radiator. Any ideas?