I've got a newly rebuilt Chevy 350 motor in my '82 TA with a new water pump, 180* thermostat, new radiator & 16 lbs radiator cap. I also have an air dam installed. When I first start up my car & go for a short ride (30 min or so drive) it runs excellent & doesn't leak a drop of oil with the engine temp reading a pretty steady 220. If I go for a longer ride (35 mins +) my engine starts running crappy (idling gets very very low when stopped at a light, etc.), engine temp climbs up to 230-235 & I notice after I've parked it I start leaking a small amount of motor oil right around the rear main seal area more towards the passenger's side. Even on a normal ride my gauage always seems to stay right around the 220 mark. Any ideas on how I could get this thing a bit cooler? Why is oil only leaking when it's thinned after the engine being hot for awhile? Any help?

I wonder if your lower radiator hose is collapsing.

Not sure? What do you mean by "collapsing"? All the hoses under the hood are new?

Old lower radiator hoses tend to collapse. You didn't say you had new hoses in your original post. Obviously that's not the issue since they're new.

Running your car too far advanced can heat your engine up to those extremes but it's not the likely cause.

220 degrees while driving is hot. It's possibly your new T-stat is stuck or not opening at the proper temp. You can test it by suspending it in a pot of water with a thermometer. Heat it up and watch for it to start opening. Read the temp.

Given the temperature I drive in daily.. I combat
this problem everyday, Its no easy task with a Firebird.

Making these cars run cool is maitenence and close
observation..and of course, the right parts.

On a 110* day, my car sits at 190-200degrees..

After 2hours of freeway driving, my car will sit
a notch before 220* ..makes me nervous, but never
moves any higher.

However, I dont think its the actual temp, but the
headers heating up the sensor really good.

If you can tune the car, get the fans operating
at a lower temperature, and keep the 195# T-stat.
You could run a circuit to manually run the fans,
but it decreases fan life, and you could forget
to turn them off.. and get stranded, hehe.

Run a 75/25 coolant mix (TB bypass reccomended)
You dont have a TB, so worries.. and some Water Wetter..Youll see a 10-15* degree drop in temp.

I can stress enough how much block flushes
help... Do it multiple times, no matter how
clean you think the block is.

Also, what weight oil are you running?

I'm using Valvoline 10-40 oil. I'm going to try flushing the radiator & using a 75 coolant & 25 water mix & see what difference that does? I do have hooker shorty headers so the heat from them running up the sensor may also be contributing to the problem as well? Not even sure if my temp guage is 100% accurate either?
I did replace my clutch fan with a flex fan as this was recommended to me by numerous members here & at my mechanic's shop as well?