The underside of my car can be described in one word, rust. Ive been thinking of and will eventually tear her down to put in floor boards or patch work which is too be determined when i get the interior out. Im more of a mechanical person though and not much of fabricator or body guy though and dont want to get in over my head, though im sure i can figure it out. famous last words right?

Its an 83 z28. and im so determined to fix it b/c it was my first car so well leave that there.

i guess im looking for advice to minimize the monetary cost of my inexperience in this area. so im just going to run off some questions and feel free to share your experiences.

Does anywhere make pre-fab floor boards? and well pretty much the whole underside would be ideal? What gauge steel should I use if i need to fab or patch? general advice? what size constitutes a patch vs redoing the whole section? best way to go about surface rust? complete and i mean complete tear down vs only tearing out the interior? general advice and comments again?

THANKS

 

id start with just putting the car on jack stands, and putting my hands all over the underside of the car, if your hand can push the metal and bend it, or go all the way through, then youll have an idea of what your dealing with. its either surface rust, or its all the way through. based on your diagnosis of what you can feel, id pull the front seats out, take out the center console and start pulling the carpet toward the back seats. if you see that rust is pretty bad by the time you get to the end of your front seat mounting bolts, then id say you should prolly so a complete tear down. and the biggest patch i would do, is a 12X12 patch AS LONG as your welding onto SOLID metal surrounding the patch. if you have to go a couple inches farther, then go for it, just make sure the metal your going to weld on to is as solid as the new metal. im not sure how thick it is, id say no thinner than 16 gauge for sure. id use 14 gauge. just make sure your welds are solid

if you have a spot thats maybe 5X5, id cut a hole 8X8 and just be safe. if you have to put in more than one 12X12 patch, id either buy the floor board replacements (if they sell those, im not sure) or go the old fashion way, and make your own.

since you say your not to skilled with metal fab, then just take a couple of pieces of scrap metal, and start welding them together for practice. once you feel confident, then start replacing little spots first, and move on up to the big spots.

after you get them all welded up and are completely done, id use some product that stops rust. i see that Bullet Rust Stopper stuff all the time advertised on this site. maybe somebody else can add a little to the whole rust prevention thing for me..

hope your floor boards arn't to bad!!

 

Classic Industries has the entire pre-fab floor boards. Pricey, but an option if need be. I'd check some other places for prices as well. Best of luck.

 

I used the Classic Industries floor in my car (I didn't do the work myself) and it worked out good. It would be the way to go if there is major rust but from talking to the guy who did mine I wouldn't recommend trying it yourself if your unsure whats involved.

 

I used Classic Industries floor pans on my 82 Z28. They fit reasonibly well. The didn't just drop in though. I had to heat them and beat them a little to get a propper fit. Along the rockers and firewall was fine, same thing with the center (probly didn't hurt that I was doing both sides at the same time). But the rear sat to high where it overlaped the old floor. Also the "humps" around the tranny tunnel were to high...the supports for the front subframe didn't fit tightly against them. It didn't bother me to bust out the torch and form the metal though, it was getting covered with carpet anyways.

If you plan on eventualy tearing it down to replace the floor, I wouldn't bother patching it. Unless you get rid of every bit of rust (or properly seal it)...it will come back. The job isn't easy by no means, but it's not extremly difficult either. If you take your time and have decent welding skills you should be able to pull it off. This was my first attempt at floor replacement (I've done quite a bit other other body work though) and mine came out fine.

FWIW: Even though I used Classic Industries pans...I didn't order directly from them. I called to get a shipping quote and it was way expensive (over $200 ), so I went down to my local Napa with the Classic catalog and they were able to order without any shipping charges. However I had to wait a few extra days for them.

 

Nothing is "drop in" on a unibody car. These things flex and you're gonna have to do some cutting and trimming irregardless unless you get REAL lucky.

Also, if you can't weld, forget the idea replacing the whole floor on your own. If you want to buy a whole floor pan and cut patches and rivet them in place, fine, but make sure you use a good seam sealer on BOTH sides of the patch (top and bottom).

I do NOT recommend riveting a floor to the rockers, which is why I said if you can't weld, forget it.

There is nothing structurally wrong with cutting out the rotted sections of your floor and riveting in a patch as long as you seal it, except that in certain areas, mostly around the edges of the floor pan, you're going to run into areas where this is not adviseable, like around the firewall, the rockers, and possibly by the rear seats (haven't looked at a bare f-body floor pan in a LOONG time).

How bad is your floor exactly?

The suggestion to crawl under there and start poking stuff is really unnecessary. You can do the same thing a lot more safely from the top. Make sure you where good gloves and eye protection just in case.

Mathius

 

My welding skills are mediocre but i have a friend for that, lol. I haven't looked at my floor yet but something tells me the replacement pans will be the route i go, as i know of atleast one through hole without looking at it closely. For those that are curious if i had to guess i'd say about 5% hole, 25% through rust, 50% surface and that leaves like 20% in good condition.

But if the fabricating is limited to trimming heating and pounding life should be good. I just wanted to be aware if anyone had been through major problems fitting them.

THANKS for letting me know napa can order them, thats probably what will happen once i tear it down.

Do these pans require any mounting or bracing aside from "welding around the edges" to put it loosely?

 

eedit

 

one more question. if i order the panels can anyone tell me how theyre shipped/packaged. the reason i ask is if i order them now what steps would i need to take to preserve them from rusting from the humidity if i dont get to it for a month or two. anything, just cover them, lightweight oil sprayed on? THANKS AGAIN

 

The pans will arrive already coated in a waxy oily substance to prevent them from rusting. I sprayed mine with POR15 before welding them in.

Prior to working on this car I have had no welding or fabricating experience, never even seen a MIG welder before.

Time is still to tell if I did a good enough job or not when I start re-assembling the doors, fenders and T-Tops..

 

does anyone else have any photos?

 

What else do you want photos of?

 

nothing in particular i was just curious of the details you cant see till you get into it. for example i have a question. the braces for the seat rails, did you buy those or cut and weld from the original?

 

The spot welds were drilled out and braces re-used. I sent them to get blasted then sprayed them with POR15 also before welding them back in. I am actually needing some photos myself of the floor towards the front of the trans tunnel, on the original floor there was a bracket welded to the tunnel, but my new floor actually has a slightly different shape to it so its hard to position the bracket (cant even remember what it was for to start with).. also there is a bracket on the underside that doesnt seem to be used for anything either..

oh well, guess i will find out someday.

 

That's pretty common in GM construction. You have the rockers, the floor pan sits on them, and then the seat braces go atop the floor pan. I would recommend to anyone that they use a good weld through primer on the underside of any panel you can't get to, for example the insides of those seat braces.

Rust will form anywhere where oxygen can get. If you can't seal it up well enough to where oxygen can get to the metal, make sure you coat it with some weld through primer.

You can choose to paint, but a lot of time that burns up and it makes your welds a mess.

Mathius

 

I have one last thing to add before you order those panels....

Make absolutely sure that stock floor is adequate for your needs. What do I mean by that? I'll give you an example... On my '76 Chevelle, I had rusty floor pans. Over half of the floor was rust. I chose to order stock replacement type pans and I welded them in. A few years later when I went to run a dual exhaust with side exit exhaust pipes (before the rear tires) I found out there wasn't room to put my mufflers under the stock floor. So now if I want to run those pipes (I do) I will have to cut that floor back out, run my exhaust, and then make my own floor over top of it.

So make sure that stock floor is gonna work for what you want.

If you're still convinced that's the route you wanna go, then get yourself a full pan, and not patch pieces. That'll save you some grinding and make it come out as stock as possible.

Mathius

 

heres some other pics. . .

https://www.thirdgen.org/forums/body...-up-start.html

 

Why would weld through primer burn off any less than any other paint?

 

so the enormity of doing this project right just hit me in contrast to a couple patch panels so im thinking i might end up going ground up.

any advice on finding subframe rails, the only ones i see online are the rears for 700 a piece which seems ridiculous to me?

anyone know where i can find a deal on a rotisserie? deals on a tig?

i am also laughing at myself as this started out as a thread on patching for idiots. oh well i'm not a big fan of expensive band aids

 

When i started tearing into my car last winter break i realized that i was over my head financially in fixing it completely to my liking so i did a temporary fix. Since i am in college and will not be able to afford the new floorpans and paint job i want for my car untill after i graduate i had to stop the rust from spreading so i could save the car down the road. I cut out ALL the rust and had a local body shop rivet and patch up my floor untill i could afford the whole panels.(cost me 100$ for the patch) Floorpans are like 200 a piece with like 150 freight charge plus i have to pay someone to install them. I also POR-15'd everything under there after grinding all the rust off.

I have some pictures of my car before/after if you would like me to post them up for you. Just let me know. To me it sounds like you got in a little over your head budget wise just like me lol.

 

yeah but looking at it long term it will be worth it. if it takes a year or two so be it. you need three things: the money to do it, the time to do it, and the know how to do it. while i have enough of each to get a good start im thinking it will be awhile before i get all three completely and am able to drive it again. if i end up going through with it, and i probably will reluctantly but theres something nostalgic about your first car that makes it worth it.

go for it. pictures are always good. thanks

 

Just so you have an idea, I started my car in August 2007 and it is now back to being just a shell.

i still have a ways to go, working on the rear wheel wells and passenger side quarter panel next.

 

i was humoring myself with the one year or two comment. i spent more than that getting the engine and trans where i wanted it. but its time to make the commitment i guess.

 

It's formulated with Zinc, I assume after it heats to temperature and cools back down, it still protects from rust, but that's irrelevant.

The real reason you use weld-thru primer is because if you try to weld through regular primer or paint, it contaminates your weld.

And if you don't coat the inside of the panel with SOMETHING, and you get air in there, you'll rust from the inside out in no time.

Mathius