When I built my 81 I installed a leMans front clip. Everything for cooling and heating was replaced with new or rebuilt.


That included a brand new copper core radiator, water pump, plumbing, and 180 thermostat.

I was told that the LeMans clip would not need the valance since the front built in spoiler naturally redirected the air properly.

To make a long story longer.

My car always ran a little warm. Around town it was fine; hovering around 190-200. But on the highway at anything above 2500 rpm, it seemed like the temp would creep up and up. Never went to the red, but certainly the 210-220 mark.

This always puzzled and eluded me. I didn't like it, but numerous mechanics, including the chevy dealer said it was ok. Just didn't sit well with me. I know that the newer motors are set for around 210, but this old iron 383 just seemed too warm for my taste.

I ran a few tests and concluded that the front clip was NOT doing its job properly. I also didn't like the copper core radiator. My buddy installed a tremendously expensive DeWitts aluminum radiator. It was really costly, cap alone was nearly $50.00.

I got to doing some serious research and decided I was not going to get a tremendously expensive radiator. What I did do was a get a two row radiator with for real 1 inch tubes. This gave me a nice wide cooling area and came with a cap. I like this one as well because it is for a manual and doesn't have the bosses to cool the transmission.

Radiator cost me $220.00. I put in a 160 degree thermostat.

I then found some aluminum plate I got for nothing. I figured that the air was being routed under the car at speed, thus sucking it from the radiator. Originally I was going to route the scoops in the front air dam to the radiator, but decided to try the valance first.

Yesterday was big test day. Over 90 degrees here, and we had a 180 mile run as a club to a car show. I ran this baby in traffic and up on the highway for a bout 4 hours total. Temperature never budged from off of the mark exactly between 150-200. It never move. Not even a tick.
Ran cool as a cucumber and never fluctuated one degree. I tried it with the heat on full blast, A/C and everything turned on. Never wavered, never dropped or went higher. Stayed dead on target.

I figure the car is probably running a little bit below 180. But not by much. I will have to use a thermometer on the motor at some point to get an exact reading.

This set up has lowered my highway temps about 40 degrees. That's pretty spectacular in my book. Fortunately my new motor doesn't have many miles on it, so I'm sure no damage has been done running warmer.

 

The later fronts are known as "bottom breathers" and the aluminum plate you installed is cutting off the air flow to the radiator. Take that plate off, put a 195 degree thermostat back into it, make sure your fan clutch is operating properly (moves a LOT of air when at operating temperature) and make sure you have the correct temperature sender for the gauge.

 

I think you were correct to install the belly plate. It looks like your front end is open in the "grill" area, allowing air to enter there, but the front spoiler is just producing a low pressure area under the car, inducing the grill air that would normally go to a (high pressure) diffuser volume ahead of the radiator to instead take the easy route underneath the radiator. The belly pan sealed the diffuser volume, and allowed the grill air to go where it was supposed to.


You did change multiple things at once, though, and I'm not convinced that the new radiator and thermostat were a significant part of the cooling improvement.

 

The plate is below the intakes with the blinkers and above the intakes in the spoiler.

So all the air from the top two now goes through the radiator and not sucked underneath.

I do believe that is a huge advantage especially at highway speeds.

 

That's what I said. What are you apparently disagreeing about?

 

I wasn't disagreeing at all. In fact i totally agree.

Just clarifying what i did. I had thought about cutting holes in the plate and ducting air from those air dam ducts to the radiator.

But i dont believe i need to do that.