My 91' 305 RS runs hot if stuck it traffic. The air dam is intact. Right now the cooling system is bone stock. I plan on adding 180 degree t-stat, with a cooler fan switch and one of those rivet-on impellors for the water pump. But what about the radiator? Is the TBI unit a decent piece? Or would one from a TPI car be a worthing upgrade?

 

What do you mean by hot. From the factory these cars are designed to run warm. I believe the fan temp switch doens't come on until 230*. The air dam has nothing to do with running hot or overheating in traffic. I 180* stat should help you run cooler. Along with a lower fan switch.
I'm pretty sure the radiators are the same from a TBI and TPI. You could always get a 3core aluminum if you're that worried about it.

 

Well most of the time the car only gets to the first mark on the temp guage. If I get stuck in traffic, it soars to the third and slowing begans creeping toward the red area. If I start driving again it goes back down to the first line.

 

Is your fan coming on?

 

I think so, it comes on when the A/C is on, and when the car first starts.

 

Ya, but that doesn't mean it's coming on in traffic

Let the engine idle in your driveway, keep an eye oin the fan and temp gauge...verify the fan does come on and note when on the gauge. If you can borrow an external temp probe, place it on the Tstat housing to get the actual temp.

Another thought, take a 6-pack in to a radiator shop near closing time and have them verify the temp for you.

 

8mike9 is right. Test your temp, maybe you could borrow someones Auto X-Ray. Your guage is only as good as the $10.00 sensor that operates it.

The modifications you suggest are good for improving your cooling design "after" it is repaired. but not to repair it. Your stock cooling system should be adequate, even though "hot by design".

~~~~~~~~~~~~~~~~
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Make sure you dont have air in the cooling system.....

And change the thermostat.

 

Next time it gets "hot" in traffic, pull over and see if the fan is running. It should be pulling alot of hot air from the radiator.