I struggled with cooling the Cleveland the PO put in my car (non AC, base) with a 20” radiator and 5 blade fan w/o thermostatic clutch. In 2017 I went on an all out assault on the cooling system-24” aluminum DeWitt rad (dual 1” tubes), FlowKooler aluminum water pump, correct Robertshaw t-stat and T Meyer brass restrictor plate, electric cooling fans (dual 11” on deep, full coverage shroud with vent flaps, new hoses with spring in lower hose, new 13 lb cap with recirc design (dual seals), recirculation reservoir, new green pre-mixed coolant, and PWM fan speed controller. No problems with temp since that installation. I had already replaced the alternator (65amp) with a 100 amp.
While the comments are prevalent, I don’t believe the bore OD has anything to do with overheating as the thermodynamics just don’t make sense to me. If the overbore is part of an overall HP increase plan that’s a different story but if the HP is close to the same as before increasing the bore, where does the extra energy come from? I can see a slight change in the rate of heat transfer due to thinner cylinder wall but the combustion heat energy does not change within the cylinder assuming power levels remain close. I’ve heard the argument that there is more frictional heat in the larger bore but the change in surface area is so minimal that I cannot accept Ford designing a cooling system that close to the bleeding edge of capability. The argument of reducing mass of the cylinder increases the energy passed to the cooling system aligns with the comments about slowing down the coolant at various spots to allow for greater heat transfer. That doesn’t make sense either as keeping it in the radiator longer to cool means keeping in the block longer and absorbing more heat. Increasing flow rate-air and water-is always beneficial in increasing the heat transfer of cooling systems.