Car getting real hot....
The coolant always expands as it heats, and hot spots in the heads make some steam pockets that also expand the coolant volume. When coolant volume grows to the point in the top tank to where liquid coolant eliminates the 1" headspace it then makes contact with the breather valve on the radiator cap seal whence that valve slaps shut instantly and cooling system pressure is allowed to build instantaneously. Once pressure is at 16-17 psi the steam bubbles in the hot spots collapse due to the 16PSI pressure thus restoring the pure liquid to metal contact necessary for best heat transfer. 50/50 Ethylene glycol @ 16 PSI boils at about 276* which greatly reduces boil overs on parked cars. As to heat exchange in radiators is concerned the faster you can flow the water through the core and the faster you can flow cool air over the core, the more Btu's will be extracted from the fluid. Therefore running the water pump shaft/fan shaft at as high a speed as possible without creating cavitation in the impeller will result in dumping more btu's into the air than any other combination. Back to the OP's problem, That shroud design is the worst I've seen. It is way too close to the core, and has no aerodynamic sweep from mounting edge to fan opening. The fan you have chosen is a very poor performer and should be replaced with a HD clutch driven 5 blade mopar fan. History lesson time: The 69 hemi a-bodies used the same 22 inch 3 core radiator and shroud +5 blade clutch fan as the 340 a/c cars did, and they did not overheat on Woodward Ave. Here are some photos of my 69 cuda 550hp 470ci A/C equipped cooling system. Eddy heads, 11.3:1 CR .033" quench height, 246* @.050" Camshaft. Timing 15*btdc idle, 53* btdc light throttle cruise. Fuel mixture at light cruise is 15.3:1. Original OEM 3 core brass radiator is offset forward on its brackets 3/4 inch to gain room for the clutch fan clearance on the big engine. The 1/2 inch gap between the OEM factory shroud and the top tank is stock and acts as a vent during high speed operation. 5 blade asymmetrical fan, and HD viscous fan drive are OEM replacements. Engine idles @800RPM in gear with A/C on and on our hottest day so far 91* resulted in some extended traffic light temps of 205* otherwise out on the road it runs at the 195 thermostat temp regardless of gear or speed. You have a fine radiator, and a usable water pump...it is your shroud and fan that are letting you down. The shroud is blocking airflow at highway speed, and the tiny bladed fan can't suck enough air at idle. OTOH those are sure nice pulleys! Best Wishes, Steve
![IMG_4788[1].JPG](https://www.forabodiesonly.com/mopar/attachments/img_4788-1-jpg.1715752968/ "IMG_4788[1].JPG")
![IMG_4785[1].JPG](https://www.forabodiesonly.com/mopar/attachments/img_4785-1-jpg.1715752970/ "IMG_4785[1].JPG")
The coolant always expands as it heats, and hot spots in the heads make some steam pockets that also expand the coolant volume. When coolant volume grows to the point in the top tank to where liquid coolant eliminates the 1" headspace it then makes contact with the breather valve on the radiator cap seal whence that valve slaps shut instantly and cooling system pressure is allowed to build instantaneously. Once pressure is at 16-17 psi the steam bubbles in the hot spots collapse due to the 16PSI pressure thus restoring the pure liquid to metal contact necessary for best heat transfer. 50/50 Ethylene glycol @ 16 PSI boils at about 276* which greatly reduces boil overs on parked cars. As to heat exchange in radiators is concerned the faster you can flow the water through the core and the faster you can flow cool air over the core, the more Btu's will be extracted from the fluid. Therefore running the water pump shaft/fan shaft at as high a speed as possible without creating cavitation in the impeller will result in dumping more btu's into the air than any other combination. Back to the OP's problem, That shroud design is the worst I've seen. It is way too close to the core, and has no aerodynamic sweep from mounting edge to fan opening. The fan you have chosen is a very poor performer and should be replaced with a HD clutch driven 5 blade mopar fan. History lesson time: The 69 hemi a-bodies used the same 22 inch 3 core radiator and shroud +5 blade clutch fan as the 340 a/c cars did, and they did not overheat on Woodward Ave. Here are some photos of my 69 cuda 550hp 470ci A/C equipped cooling system. Eddy heads, 11.3:1 CR .033" quench height, 246* @.050" Camshaft. Timing 15*btdc idle, 53* btdc light throttle cruise. Fuel mixture at light cruise is 15.3:1. Original OEM 3 core brass radiator is offset forward on its brackets 3/4 inch to gain room for the clutch fan clearance on the big engine. The 1/2 inch gap between the OEM factory shroud and the top tank is stock and acts as a vent during high speed operation. 5 blade asymmetrical fan, and HD viscous fan drive are OEM replacements. Engine idles @800RPM in gear with A/C on and on our hottest day so far 91* resulted in some extended traffic light temps of 205* otherwise out on the road it runs at the 195 thermostat temp regardless of gear or speed. You have a fine radiator, and a usable water pump...it is your shroud and fan that are letting you down. The shroud is blocking airflow at highway speed, and the tiny bladed fan can't suck enough air at idle. OTOH those are sure nice pulleys! Best Wishes, Steve
