help i have a 77 280z that was given to me . Got it running it will run decent when you first strart it but after 5 or 10 minutes the engine starts to sputter and backfire then it will die . when you try to re start it the engine barely will turn over almost like the starter is trying to overcome exaust blockage. any help or advice any one can offer would be most helpfull

Could be a number of different things..Not sure if they used a catalytic converter in 77, but it could be plugged. To check, start the car when it’s dark outside, and let the car run for a few minutes, and if it’s plugged the converter will be extremely hotter then the rest of the exhaust to the point where it could be glowing. If that checks good, or it just doesn’t have one.., I would be checking the timing to make sure it’s within specs.

Could be a fuel starvation issue as well. Z's have alot of problems with rusting tanks. Try changing the fuel filter before doing anything else (Autozone $9). On the other hand, it could be the exact opposite and your getting too much fuel causing the plugs to fuel foul. Next time you have this problem pull a few plugs and see it they are wet. Check all of your vacume lines especially the one under the intake manifold that comes off the PVC valve. They have a bad habbit of drying up because they sit so close to the manifold and they almost always crack on the back side where you can't see it. Temporarily disconnect your thermotime switch the next time you have this problem to see if runs better. As you go from the easy, cheap and obvious things you might want to pull your injetors to see if they are all firing (leave them on the rail turn over car). These are all problems that I have had with a Z that sat too long.