Me and my son went out to run some errands in my 88GT today. I live out in the country so the roads around here are all 55 MPH plus back roads. About 3 miles from the house I had to stop at a stop sign and noticed that the car wanted to stall. I looked at the guages and noticed that the battery light was on and the guage was reading low. I told my son that we had better hurry up before we loose all power and the car quits. I took off from the stop sign and looked at the temperature guage to see it pegged past the red. I immediately thought that it was not reading right due to the low voltage issue (no alternator). The car was running great as long as I didn't slow down. I made it about 3/4 mile from the house until the car just quit. I called my wife, she brought my truck and we towed it home. I have the car in the drive-way and start really checking things out. The belt is gone, so not only was the alternator wasn't turning but neither was the water pump. I think back to that temp guage and want to kick myself!!!! I put a charger on the battery and after a while tried starting the car to pull it into the garage. It started right up, did not miss, knock, tick of sound any different than it did before. I pulled it into the garage, reved it a few times (no smoke) and shut it off. The only thing I have notcced is anti-freeze in the front where the cap relieved pressure and on the back tail lights is a thin film of oil. That oil worries me. There is no oil on the engine, leaking from the engine no anti-freeze leaking. Its all very clean. This engine has approx 51,000 miles on it It is the 2.8 that I removed from a formula. I checked the water pump and alternator to ensure that they are turning freely. I plan on getting a belt and installing it next week. I noticed no oil in the anti-freeze but then again, the water pump wasn't pumping and I notice nothing strange with the oil.
What are the chances that the engine is toast??

Flush and fill the cooling system, change the oil and cross your fingers.
You might try a compression check to see if there's any hint of a leaking head gasket. You could have warped a head, but the cast iron 2.8 block and heads are pretty durable.

If after new oil and coolant it seems to run ok, run that oil for a normal interval, then get an oil analysis done to see if it's getting excessive coolant, bearing material, etc. in the oil.

It will probably be ok if it's not missing when you start it up. The film on the tail lights could just be antifreeze that was blown under the car while driving. Replace the belt, thermostat and flush the system, drive it & see what happens. I've had cars in the shop get so hot they melted the radaitor top plastic tank but the motor ran fine afterwards.

RPO's Fiero coupe did that a few months ago. He just pulled it in to a parking lot and I drove him back the next day and replaced the belt and I don't think he had any issues with the car since. Lesson is to check out the condition of tour belts.

I've severely overheated a couple of these 660 engines without a problem so you have a good shot at there being no damage.

Thanks for all of the replies. I'm feeling pretty good about it. I will have to find my spare belt. I plan on going out in a bit and putting it on and seeing how things go.

The only issue RPO had was all the coolant that came out when the engine was hot. Take extra coolant with you when you restart the car.

Refilled the car with coolant, and checked the oil which was at proper level. I started the car let it warm up adding coolant as needed. Let the car get up to temperature in the driveway. The car got up to temperature, radiator fan came on, no leaks, no smoke, no strange smells. The only difference was there was a slight miss at idle. I could rev the car and everything sounded the same. I went out, took it for a drive. The car drove and sounded great. Ne hesitation when I got into the gas but when I would slow to a stop the car would have that slight miss. The idle would also hunt. I drove the car back home and proceeded to check a few things. Maybe not the right things but I checked them anyway.
I thought about timimg. I don't know why timing would change with an overheat. I did the procedure and found the timing at about 12 degrees, trunklid said it should be 10 D automatic. I couldnt even begin to set the timing because the mark would not stay at an even mark. The best I could do is average. The car would not run smooth enough for me to set the timing. With the overheat I thought maybe some plugs fouled (I know.. Probably not but I was grasping) I started unplugging one wire at a time as the car idled then I would plug it back onto the distributor before unplugging the next. I only made it to a few. Several would make an instand difference as soon as I would unplug them. One going to the fron of the engine (between firewall and engine) made no difference at all. I went ahead and replaced that plug and wire. It still didn't make a difference when I started the car back up. I finished for the night. I have to work early. I don't understand why everything is so good when I'm driving, just to have a rough hunting idle. Temperature is good, oil pressure is normal compared to what it was before. No smoke, no smells. I washed the car, got the oil film off the back. I probably drove the car 8 miles today. Drove it pretty good just to see how it would do. No oil film on the taillights. I'm at a loss. The only thing I know to do is change the plugs and plug wires and see how it goes?? Is that a waste of time?

If its only one cylinder that acting up, swap a known good wire and plug. If no change, replace cap and rotor.

I have had a belt break and my car start to overheat, I used my shoelaces to get the last like 2 miles home. It worked.