I have a 1991 Z28 5.7, mostly stock. I have all stock componants for the cooling system, and all are working as designed. When driving, car runs about 180. But after idleing for about 10 min, temp climbs to 235, and fans come on as designed. But I'm worried that in the summer time this could be a problem. Would upgrading the radiator help? If so, which one fits/works the best, price not important. It seems to me that since the water pump is only turning at 500 rpm its harder to keep engine cool. Any suggestions appreciated. Thanks.

 

did you check for obstructions? plastic bags into the radiator will do it every time. and stuff gets caught between the radiator and needs to be cleaned out like the rain gutters in a house.
it helped with mine.

 

If you want to keep your car cooler, have you considered putting in a switch?
I bought my car with the ground for my fan hacked and had a constant ground so it ran all the time, then I just put it on a switch so i could get the car to get hot faster on a cold morning when i wanted some heat.
it was very convenient to me though because I had pre existing holes cut in my console on the side of the radio by where your leg would be.

its real simple to do, all you need is a switch from autozone, and some 14 gauge wire(i believe it was)

the hardest thing to do for me though was reaching my hand behind the brake booster to be able to route my wires through the firewall
beware if you have big hands like me

 

Radiator is clean,no obstructions. And both air deflectors are there. I thought about putting a switch in, but that doesn't explain why the temp keeps rising in idle, unless that's normal. Water pump is newer, thermostat is new, and switch is new. All are working as designed. Would a higher capacity aluminum radiator help at idle?