I purchased this car about 10 years ago. It had a LS7 454 crate motor in it. Ran great and never exceeded 180°. Along with the LS7 engine I also received the numbers matching 396-325hp with the car. I wanted to return the car to original so I had the 396 freshened up (.030 over bore) everything was kept stock. Well now for 7 years I have not driven the car due to a over heating issue. It had the same radiator (4 core) as the other motor, same original fan shroud and at first the same temperature control fan. I can not get the motor to run any cooler than 230° and on hot days 250°. Here is what I have done. Taken it to at least 8 shops no improvements, replaced the 4 core radiator (American Radiator over $1000) with a new 4 core radiator with 3/8 spacing, 3 new water pumps, 5 different thermostats, 2 new radiator caps, new temperature controlled fan. I had the engine completely torn down by the rebuild shop and scoped the internals heads and block, found nothing. The engine builder has no idea what is causing it to run hot. When you go on the expressway it will run hotter. I don't want to just look at the car for another 10 years. My best guess is that I have trapped air but have followed the procedure to remove trapped air dozens of times (raising the front of the car with the defrost on all the way and radiator cap off). If I had the LS 7 I put it back in but sold it. It is a 4 speed car with factory air conditioning. Any help would greatly be appreciated.
Recommend read thru this:
A bunch of ;blah, blah, blah, not specifically related to your car. But, near the 'end' of that thread, that owner reverted to OEM GM style cooling system.
Look at the pics of that owners electric fan set up. I am not surprised. Does yours have that much blockage of air flow thru the radiator while going at forward speed?
Fans, electrical or mechanical, should only be needed at idle, or very low speeds. Wanna try something? Take the electrical fan off (remove all the air flow blockage) and take a drive where you may go a continuous 30 mph or so. IF you stay close to the thermo setting (180F, + about 10%, is a good range. 180F being the thermo setting), your cooling system is doing its job in THAT application.
For idling and traffic applications (basically the same condition, not enough air flow thru the radiator), add a properly installed (the way GM did it) mechanical fan/shroud. It's 'normal' (in my option) if the car's temps go 'up' another 10% TEMPORARILY in those conditions (if they return to normal upon regaining forward speed). OEM style 5 blade with the clutch is a popular choice. The clutch doesn't improve cooling. It de-clutches the fan when temps are low and the fan is not needed (at forward speed).That allows the torque used to rotated the fan to be used for propulsion (a nice slick concept). GM used the 'clutch fan for high hp engines and those with a/c. Same reason, redirection of torque to a more useful 'need'.
It is POSSIBLE to have sufficient electric fan capacity to handle both 'applications'. I do know how much that is. GM engineered their cooling systems. They work.
A 50/50 mix of antifreeze/water boils at approx 260 F at 15 PSI.
The 'idiot light' for my '63 Impala does not 'glow' until around 240 F (GM anticipated higher temporary temps).
AND, as already mentioned, make certain the timing is correct.
Just trying to be helpful.