A few more tips:
Aside from any issue you might have with the clamp itself, you wish to ensure the outlet of the radiator, heater core, water pump, thermostat housing are in good repair and ROUND before attempting ANY clamp. Heater core nipples or radiator connections can be checked or straightened as needed using a correct size socket or pipe inserted into them and tapped straight carefully. A reused hose can cause issues also since the clamp can bottom out before tightening enough. As mentioned, a black RTV sealer (such as "The Right Stuff" by Permatex) can help some with sealing against shrinkage (over time a radiator hose shrinks at the clamp from expanding & contracting, a reason the "spring-type" clamps have been adopted on newer vehicles)