Automotive Sheet Metal Repair Tips/Tricks

[ClassicTractorProfessor 5,314]

A month or so ago I scored a really good deal on this 1982 Chevy C20. When I found it one of the first things I noticed was the lack of rust in any of the common areas these old trucks tend to rust out. Few weeks ago we pulled it up in front of the house and started messing with it. First order of business was to clean it out, as it had been sitting several years and smelled horrible inside from all the mice that had been living in it. Carpet was coming apart in shreds as we tried to vacuum it, so I decided to just go ahead and rip all the nasty old carpet out, and that's when I found the hidden rust in the floor pans and inner rocker panels. If this was gonna be an old beater farm truck I'd just screw some sheetmetal or old license plates over the holes and call it good, but my plan for this truck is to eventually pull our tractor to shows with it so I want it done right. 

 

I know the easiest way to repair it would be to load it up and haul it to the body shop in town, but I also know that I hate paying someone to do something that I could potentially do myself. I have new floor pans, inner/outer rockers, and cab corners at the shop waiting to be put in, soon as I get my welding cart finished I am planning on taking the 82 over there and beginning to attempt to tackle this project on my own. 

 

When it comes to the mechanical part of this old truck I can make the old girl run like a sewing machine again, but when it comes to body work and rust repair I'm wandering into completely new territory, do any of you have any tips and tricks to maybe help a complete novice such as myself as I begin this project? 

[Pullstart 62,836]

You find all the good ones Bryce!  Did you keep the other square body dooryard find too?  
 

A few things I’ve learned about body work….
 

Only replace what you have to.  Save as much good sheet metal from the original as you can.  Repop panels are great.  They still might not fit perfect, so use as little as possible.  
 

When welding, jump around.  @19richie66 shared an article with me about welding process on sheet metal.  Often most people do a tack every inch or so, then grind, then tack, then grind, etc.  ALWAYS PEEN THE TACK WELD BEFORE GRINDING IT OFF for best flat results.  Start on the panels you won’t see and get used to welding sheet metal.  
 

Though welding is great, check into gluing panels.  It seems that rust prevention in the future is easier when you don’t introduce a bunch of welding to it.  Though we all get better with welding, there will still be pin holes here and there.

 

Get everything straight and true as possible without bondo.  Like the welding pin holes, bondo can trap moisture, crack, shrink, etc, if used too heavy.  
 

TAKE YOUR TIME and don’t rush the job.  Enjoy your work though tedious, and it’ll come out better than you give yourself credit for!

[Achto 27,565]

2 hours ago, Pullstart said:

Only replace what you have to.  Save as much good sheet metal from the original as you can.

 

I'm with Kevin on everything but the above statement.

 

I usually set the new panel over the top of the old panel and mark around the out side of the new panel. I then cut the old panel out leaving no more than a 1/2" of material for an over lap at any splice area.

When replacing your cab corners & rockers it is easiest to remove the front fenders and slide the box back. Do not remove the doors. You will want the doors on to check fit before welding them in place. If your new floor panels do not have the inner rocker on them you will need to make new ones. The inner rocker turns the rocker panel into a tube for added strength. New outers without good inners leads to sagging cabs & doors that won't close properly. Take a good look at your cab mounts too, they tie into the rest for strength. 

 

A 5/16 pilot point drill bit works great for drilling out spot welds. It allows you to only drill through the first panel with out leaving a big hole in the second panel.

 

Gluing pinch seams is a great idea, much more rust preventative that spot welding or through hole welding. Any butt or lap seams should be welded. When done make sure all seams are well under coated.

 

In the late 80's early 90's I did more than 30 square body rusto-rations. Normally 2 fenders, 2 wheel wells, 2 doors, 2 box sides, rockers, cab corners, floors, & tailgate.

 

A basic thought on body work is, just simply try to copy what the factory did. No need to reinvent anything. 

Edited March 18, 2023 by Achto

[ranger 1,750]

In situations like these, YouTube is your friend. Countless videos on all aspects of body restoration, with all kinds of tips, advice, etc. you may even find one with someone repairing the same truck you have?

[ri702bill 8,316]

If you are going the aftermarket repair panel(s) route, do yourself a favor - buy ALL the panels from the same brand. Not all replacement part dies are the 100% same as factory parts...

Same goes for mix & match on exhaust systems.....

[oliver2-44 9,739]

As said above, glue in as many pieces as you can. The new 3M body panel glued are amazingly strong. New vehicles are put together with the stuff. No distortion from welding and grinding. Use Evercoat body filler.  It’s a little pricier than Bondo brand. On the rusted floorboard that you keep, wire brush it fairly clean and use Rust-ban treatment and paint on it.  

[ebinmaine 67,431]

3 hours ago, Pullstart said:

TAKE YOUR TIME and don’t rush the job.  Enjoy your work though tedious

[ClassicTractorProfessor 5,314]

Thanks everyone...just one more reason why I say that RedSquare is hands down one of the best forums on the net, so much knowledge and expertise on ALL things here. 

 

All the sheet metal parts I have came from the same supplier JL Fabrication, with the exception of the front cab supports, can not remember where they came from. I went ahead and ordered everything, I'd rather have it and not need it than need it and not have it. 

 

@Pullstart which other square body are you referring to? This truck is the one i bought from the neighbor man, along with the wife's 1961 Bel Air. If you're talking about the old 81 C30 that came from the impound lot I work at it is long gone. That poor old truck looked good from a distance, but suffered from rust issues way worse than this one, as well as a completely shot front end, broken rear leaf springs, electrical issues everywhere, the list went on and on. Ended up giving the flatbed off of it to a buddy of mine, and selling the rest to another guy who has way more money and time to throw at it than I do. He's going to fix it up and put a wrecker bed on it. Though now I wish I had kept it, one of the other plans in the future for this 82 is to swap in a SM465 behind the 400 small block, that truck would have been the perfect donor truck for everything I need to do the swap.

[Pullstart 62,836]

Oh yeah, same rig!