1984 s-10 Overheating problems

I have a 1984 S-10 Pickup with a 2.0l and a 4 speed trans and it is overheating. I replaced the thermostat and the radiator cap, I took the thermostat completely out and ran it without a radiator cap to see if the coolant was circulating and it was. I had it sitting idle for 2 hours and didn't have any problems but once I go down the road and reach around 50 mph it will start sputtering and popping and when I pull over the coolant is bubblingbut when it first started overheating it ran fine until the light came on and I could let it cool down for a few minutes and I would hear the coolent rush in through the thermostat. Does anyone have any ideas on what my problem could be?? Also what are the possibilities I caused some serious damage by running it hot? I did let it cool down at all signs of overheating so.. any help would be appreciated. Also I want to add not knowing the relevence of it but I can put my hand on the fins of the radiator adn it is not hot except for at the top.

It sounds like you have a clogged system. Assuming you checked for a leaking head gasket already, it sounds like you could have a clogged rad. Pull your rad and flush it, make sure it has a good flow. This is assuming again, very important, you have checked for a head gasket problem first. Also running it hot will cause damage if not corrected. You will damage the engine/blow a head gasket if you continue to run hot. The sputtering sounds like its a result of the engine getting just too hot/overheating.

Read my thread. http://www.automotiveforums.com/vbulletin/showthread.php?t=729213

I agree with blazes9395. This sounds like a plugged system. How was your coolant? When did you last flush this out? It may be time to flush your system.