I was driving down the highway with my 88 SS, and going 65-70, the engine started to backfire a couple times and died once I pulled to the side. It still cranks with slight backfire to it but won't start. Temp is normal. What could it be

 

By the sound of it my guess would be that your timing chain went out on you . To check put the engine on top dead center (o degree's) on the timing tab and then take off the distributor cap and it should be pointing at #1 plug wire or # 6 plug wire depending on which stroke the engine is on to check if the timing chain gear has worn If it isn't close or doesn't point to either one the chain has probably worn out. Another way of checking it is either to take off distributor cap and see if rotor spins when engine is cranking or take off oil cap and look at rockers arms and see if they are moving up and down when the engine is cranking , Good luck.

 

Sounds like timing or a major vacuum leak. Does it have the original timing chain and gears?

 

So I loosened up the distributor and advanced it, it actually started but ran a little rough. I tried advancing a bit more but couldn't move any further, the 1st piston spark plug wire wasn't even pointing at the 1st piston anymore. It did idle on its own but it began to retard on its own, probably because I didn't tightened it enough advancing so far. So is it most likely that the chain jumped a tooth??

 

Most likely, I just bought the car with 66k

 

Yes odds are it jumped on you being it's 30 years old and all. t's really not that tough putting a chain in though only hassle is the taking the oil pan off to clean or replace the oil pump screen. I would highly recommend getting the 1 piece oil pan gasket from Fel Pro it makes assembly a breeze.

 

The factory 305 came with a nylon tooth cam gear to reduce noise and they wear easily. I replaced mine with a dual roller.

 

i just bought a comp cams magnum double roller and a street fire hei distributor.
i recently had to change the tps to get rid of the check engine light.

 

Here is a funny story. My S belt was shredding so my husband replaced it. My 2001 Monte Carlo SS was just turning off while driving down the highway. It was starting after a little while. It only happened here and there. I even took it to the Chevy dealer , could not find anything wrong. My hubby finally found a piece of the S belt was stuck and it was hanging down right across from the drive shaft sensor. What a hoot!