85 camaro. not stock motor. vin shows a v6. this has a 305 2bl carb. radiator has that thick white icky stuff in it. whats the best radiator flush/cleaner for this. thanks

 

When they get like that, they should be taken out and to a radiator shop for professional cleaning, where the tanks are removed and the passages rodded out. However, it may be more economical to put ina new one. That white stuff could be old sealant or aluminum oxide. Probably because no antifreeze was used or it was not changed regularly, and aluminum parts got corroded.