Transmission blew at 110,000 km.
Computer module blew 2x in 1 week, cost $1500 to fix it.
Engine threw a connecting rod at 115,000 km.
Well, when this car actually ran properly, it was a real smooth, fast and frisky ride. Unfortunately, I only owned it for about 4 months, and about half that time it sat in the repair shop. Talk about unreliable. Was the absolute worst car I've ever owned in my life. They may look sporty, but the reliability is not there. Before the engine blew, the car had over $3000 in repairs in less than 3 weeks. That's not very good, considering the car looked mint in and out, and had only 110,000 km (65,000 miles) on it. Never again will I buy a piece of junk from GM. EVER!
I own a 1990 z 24 and I have had no major problems with it. Besides the usual maintenance, (brake pads, regular oil changes, keeping fluids up, etc.) it runs like a dream. But one thing you must know when going into buying a sport car like a z 24, of any year, is the fairly good chance that the previous owner was a kid or someone that drove it to the ground and then sold it before it fell apart. So if you don't know much about vehicles and don't know what to look for when buying one, or you are not a good judge of how hard the car has been driven, stay away from it. Just don't go and complain that they are not good cars because you can't fix it yourself for cheap. They are good, if you can find one that has not been driven hard like mine. It took me 2 years to find mine but they are out there.
I also own a 1990 Chevy Cavalier and I have had no major problems with it. The usual maintenance and an ignition modulator, none of which were hard to fix. My car is my baby and is definitely one of the most reliable vehicles I have ever came across. I find it hard to believe that the problems you encountered were because of the car. I would have to agree with the previous comment that the former owner must not have taken good care of the car. I wouldn't base your theory about junk from GM on one car. GM is a very reputable company and I would not buy from any other company since owning this car.
I never had any problems with my '90 Z-24 and I drove it harder than any other car I have had including my two 5 liter Mustangs. Whoever had the car before you obviously didn't keep it up right and probably abused it way too much. You said your previous car was a Tempo, though, so you should be really used to problems!! Now THAT is a piece of junk!
I had a red 90 z24 3.1 stick was the best car I ever had. I got it with 140.000 miles on it. Before I took it, it went through 6 people in my family no problems. I did blow a tranny and 2 motors. When my mechanic brought it back to me after the first motor was installed he ran it through all five gears smokin the tires. When I blew the tranny I had a hard time finding another one but I did. The body started getting rough bearing in the motor was starting to go was a shame cause the car was great. Ended up buying a first gen ford probe 5 speed turbo had the sme handling was a bit more aggressive so I retired my cavilier in the best way I saw fit didn't want anyone to take it running so I got my cash out of it. I ran that engine to the point it was boiling hot and cracked both heads to the point of being able to fit a tooth pic in the cracks. I do miss the car so much me and my fiance just picked up an 89 gen 2 stage on z24 and I am currently looking for another 90 z24 with the getrag 5 speed.
I think you should find something more durable or slow down a bit!! 2 motors and a tranny is ridiculous... learn how to show restraint when beating your car!! You are going to go broke soon. Plus there is NO WAY you can smoke the tires through all five gears in the Z24 (unless you are sitting on a patch of ice that is). It would have to be a heavily modified car to even come close to that... but even then the upper gears are too long for that to happen. You would be upside down in the ditch from the major torque steer ripping the wheel out of your hands if you even attempted to put that kind of power through the front wheels of a car. I would also find a new mechanic if they tried doing that with my car. Write facts not pipe dreams...