overheating problem on a 73 riviera

i have a 72 skylark with a 73 riviera 455 rebuilt top to bottom honed and cleaned with full rebuild kit. i have a three core radiator that i picked up at a local parts store with a flex fan that pushes good air. Also an electric fan on the front of the radiator for a little extra cooling power. I have tried running a little rich and tried different thermostats a 180 and a 195 but still when i am at idle between 650 and 800rpms i cant keep it cool and the engine heats up quick even when it is around 70 outside. I was wondering if anyone had any idea how i could cool it down i really don't wont to fork out the $400 to $500 for a 4 core radiator does anyone sell a performance water pump or any other ideas will be great fully appreciated.

Buicks tend to run hot. When the water pumps start to wear out, they'll heat up, fast. A lot of owners have had problems with using rebuilt "Pep Boys"-style water pumps. Some of the manufacturers just replace the seals and grind down the original pump fins to remove the corrosion. The fins get smaller, they don't move as much water, the car overheats.

There are two different Buick 455 water pumps- "short" nose and "long" nose. Make sure you have the right one. Having the fan in the shroud the right depth is pretty important

Also, ditch the flex fan and install a good fan clutch and seven blade steel fan. Put in a real temperature gauge and see what your coolant temp really is. A 15 psi system is rated to 247*F boil-over. You may want to check the radiator cap- if it won't hold pressure, you're in trouble. new ones are cheap and available

Also make sure your coolant overflow is hooked up. You swapped the '73 Riv's motor, but what did you do for an overflow? Did you hook one up? Don't let anyone tell you it's not needed. They don't know Buicks well in that case in my opinion. The Riv had one, a GS455 had one, and you should have one. It is an integral part of the system- it's not just for 'extra' coolant, you need it to keep the radiator at overpressure versus atmospheric, which is how the system works.

What fan shroud did you use? there are differences, not just any 455 A body shrouds will be correct. there are two opening sizesused, off the top of my head I want to say 18" and 22". You need the correct one (I hope you're using a shroud, it's not there to protect your fingers)

The '73 Buick Riviera fan shroud will drop into a 1970 to 1972 Skylark/GS/GS455/GSX with almost no modification. How do I know? I did this motor swap into my '70 Skylark Custom convertible, using a '73 Riviera as the engine donor, back in '91:smile:

455 Buicks do tend to run a bit on the hot side, in my opinion from scale in the coolant passges after 30-36 years of use, but in my bored out 455 (overbore can add a few degrees to operating temp), I never see over 220*F on the hottest (100*F) most humid summer days, on the highway at 80mph. Around town, below 40 mph, the temp won't go over 180*. I won't get excited until I see my gauge read 230*F. then I'll shut it off but it's never happened- this car is a summer daily driver, no show queen

First step is to see how hot you're really running. If you;re around 210 at highest, I wouldn't sweat it unless it gets worse