Well I took my CO alarm with me today and I tried it out on the car's cold start by starting the engine and quickly going to the exhaust with the CO alarm in hand. It got a reading of 193 when it was placed right in front of the exhaust and after about a few seconds, it dropped to 35 and then after a total of like 10 seconds went to 0. Since the alarm has a button for "peak reading" I took out the battery to reset the alarm so it wouldn't have that saved, placed the alarm in the back seat and drove around with the rear windows cracked open. I tried the best I could by moving the meter around to where my head was, putting it in the front seat with the front windows open as well but nothing, I couldn't get a reading from the alarm anymore despite driving on the highway, in the city and all that jazz with the rear windows open. Cars really are a whole lot cleaner than they used to be.
It was a 1980 Pontiac Bonneville Safari, and last I saw it the car had well over 200,000 miles on it, with no problems.
Well carbureted cars run a lot dirtier on the whole compared to fuel injected cars so while it may run fine, it's probably running much more rich than neccessary and would be a great reason as to why they pollute so much more. A 1980 light duty vehicle (car) is allowed 2.0 nox, 7 CO, 0.41 THC grams per mile at 50,000 miles. A 1979 car is allowed 2.0 nox, 15 CO, 0.41 THC grams per mile at 50,000 miles.
I think that opening the front windows is a little different than you might think . . . the air flow over the windshield travels around the car at higher speed past the front side windows and acutally draws air out the front windows especially at the front of the window openings since there is a bernoulli effect happening at the side windows - high velocity = low pressure which draws the air in from the rear of the car but is also lets some air in further back in the window opening. Keeping the side windows closed and using the vents in the front should take care of any air flow issues with the rear hatch open since there is pressure from the windshield area forcing the air into the vents in front. There could be some turbulance in the back from the side vortex which could blow air into a rear opening however.