I just purchased this 86' camaro iroc 305 TPI automatic. The electric fan is rigged to come on at startup, I took out a 160deg thermostat and replaced it with a 180deg, flushed the system and replaced the hoses. It runs around 180 around town but out on the highway it runs up to 220+. My only thought is the 50/50 antifreeze does not have time to cool at high RPM. Any other toughts or changes to try. Thanks

Are you sure you got that the right way? Hotter on the highway and cooler around town?

Yes sir, I know it sounds strange but cools right down at idle. I even let it idle for 15min it sat at around 180.

is the air dam in place and in acceptable shape?

Air dam is perfect, thinking maybe also that the fan should stay off at high speeds. I'm sure the wind blowing at 65mph is alot faster than the electric fan.

220 is fine for these cars. Thats the way the factory made them, to run a little hotter. If it creeps up around 235 or more I would be worried

check and make sure the lower rad. hose is not colapsing when the rpms rise. i was having the same problem for the longest time, it was the rad hose.

I agree with that. 220 is not a bad temperature for a stock engine, but the running hotter on the highway than around town is...indicative of something not normal, at the least. I'd look into it.

You flushed the system, but are you sure it is flowing enough. Mine did the same thing, would go up 2 marks when I increased from 70 to 80 mph. At idle, turn on the a/c and it rose as much as 6 marks on the temp gage. The radiator was not flowing enough. Put in a new one and it now runs about 170 at 80 and 180 degrees with the a/c on at 80.