[joe_padavano]

I have to say that I've never had an overheating problem with BBO in any state of tune. There's clearly something wrong. It could be blockage in the cooling jacket, it could be a very small head gasket leak, whatever, but your combo should not do this even when sitting in the driveway.

I also caution everyone that the number of rows in a radiator is not an important metric. It's the total surface area of the tubes that matters. Many aftermarket aluminum radiators use tubes up to an inch wide. My 86 with 307 has a single row aluminum radiator and it runs cooler than the OEM three row copper unit. Most big block aluminum radiators use two rows of the wide tubes and they cool just fine. The issue with either corrosion in the radiator or crud that's worked loose from the block and is plugging the radiator is a good point and should be checked.