I'm a HS student considering to buy 240-280z. A big problem that seems to keep popping up is the rust problem(s). In a pretty bad situation, how much would it be to fix that?.. or, can you do it yourself in any way? Thanks.

In a "bad" situation you'd be better off jacking the car up real high and driving a new one under it. Ignoring the typical amateur Bondo jobs, proper rust repair requires cutting metal and welding new metal in place and trying to do so without sacrificing structure integrity. There are replacement panels available from a number of places but it can end up being more trouble than it's worth. While I've never attempting welding it is something that takes a lot of practice to do right.

is it possible to just sand it off?

Yes, you can just sand it off if it's only surface rust but then that's not a "pretty bad situation". Perhaps you can describe in more detail where the problem is. If you can upload some pictures that would be even better.

Since the Z is of unibody construction rust

in the right places will make the car unstable structurally.

Floorpans, frame rails, ect. all play a role in how sturdy the car is.

A car with too much rust can be bad, because the car's overall structure is weakened.

Too much HP on a rusty car has been known to tear them apart.

It all depends on where the rust is and how bad it is. I would suggest uploading pics to this thread and to explaing what you mean about a bad situation.

If there is too much rust then the car may not be worth any further attention.

just my $0.02

I've posted pics of my 510 before and the really rusty floors. I've had another body guy look at it and say that its ok to do work on it. (I had another that wont touch it) the third one is going to weld it for me

So instead of new sheet metal, I have a donor floor that is in very good condition. I have to take up the sound deadening mat and see what its like underneath. My question is what should I use to remove the old undercoating from the bottom, since it is already out. im gonna screwdriver chisel the rest and then por 15 after the floors are welded in (and when its summertime) so I'm looking to start soon.

what would you guys suggest?

thansk