Learning to weld - replace trunk pan?
 

I’ve done a little welding with my Hobart Handler 140- mainly spot welds which I feel pretty comfortable with. I plan to continue practicing and would like to replace the center trunk pan and a gas tank brace in my 69 bird next winter. Is this typically a very difficult job I should leave to a pro? Any tips or pitfalls?

Using below parts:

https://www.topflightautomotive.com/...IaAlSwEALw_wcB

https://www.topflightautomotive.com/...EaAkaqEALw_wcB

I think that will be a good first weld project. What type of steel have you been practicing with?

Replacing the pan is pretty easy. You will have to drill out the spot welds on the support you are saving. Once you have the new part in-hand you can lay out the cut lines. You'll cut out the old lower portion and lay the new piece on top of the old trunk surround. The original GM steel you're plug welding to, needs to be solid, as well as the support you are saving. You might consider replacing both supports. The pan will require lots of trimming and fitting.

I would purchase the parts from Ames though.

Thanks for the tips. I’ve been practicing on sheet metal removed from the same car’s side cowl area, which was replaced by a friend. If I replace both tank braces, do I plug weld them to the trunk pan before welding the pan to the car?

Cleco buttons are super handy for sheet metal projects. Good practice project.

https://www.summitracing.com/parts/s...SABEgIDOPD_BwE

Yes it easier to mount braces to pan first.

Don

The GM sheet metal welds very easy without burning through, the aftermarket metal will be a bit more challenging to master.

After you drill out the spot welds and remove the braces, you’ll see witness marks where they were. Cleo’s are nice, but I’d just use #10 self drilling screws and/or vise grips to hold parts in place. Just test fit all the parts, even tank. When you’re happy with fit, tack weld and check again.

This guy has some good videos

https://m.youtube.com/watch?v=-DvzUkMQGlk
Some good tips
When I weld on panels I always butt weld , and I use stainless wire so that my welds dint get rusty It’s hard as hell to grind though so keep your welds as small as you can. Low heat so that it doesn’t weld hood til it fairly hot will help with burn through and if you can back it up with copper that’ll help with burn through as well .
I also like to lay the gun on an angle across the butt joint so that the weld starts on full metal and ends in full metal and lays the rod across the joint. You dint get as much penatratiin this way it kind of lays the weld across the top but sometimes it’s necessary w thin metal


https://www.eastwood.com/stitch-weld...fb605bb2f1b360

Something like this can help hold panels together can’t really use clecos and but weld

I was going to suggest Fitzee, too. He does great sheetmetal work.

That dud has some skills!

Haha, everybody beat me to Fitzee. I’ll still throw in my recommendations for must watch vids of his though.

https://youtu.be/6Fvjq9Xie8Y

https://youtu.be/_u31t13QO6A

That guy is a genius and his tips will honestly make you a better welder/fabricator with practice.

I don’t have any specific MIG tips as I only TIG stuff now, but if possible I always butt weld like Turbo69 mentioned. I usually try to cut near some sort of bend or “structure” if the job allows. It’ll limit your warpage. Not on a bend, just near it so you have the advantage from it. Skip all over with your tack welds so there are no surprises. Also be mindful of your grinding afterwards. You can hand file some heavy welds down or use a fresh 40 grit briefly instead of grinding that same spot for 5min with with worn out 220 and nearly making it turn red. Sometimes it also helps to practice on an even thinner gauge to hone your skills. I did so much 19ga recently that it makes the 16ga I’m doing now feel like plate.

Biggest tip I can think of would be the fit-up. If you can make your new piece fit in your cut out area with a near friction fit without seeing daylight, your job will be way easier. 3M makes Cubitron .030/.035 cut-off wheels that are worth every penny.

Fitzee is great! Love watching him. I like the fact that he uses only basic tools like most hobby guys would use.
That said, I haven’t started welding yet but he makes it look like I can handle it. Bought a Hobart 140 when it was on sale.

Don’t know if anyone mentioned wire size…but you want to run .023 wire for sheet metal

I would buy the eastwood sheet metal holders that keep panels parallel, and butt weld the trunk pan. Only plug where it was spot welded. Done this way, with patience, you really can't tell its been replaced.

Thanks - I've been using .023 for practice

Do you mean these? https://www.eastwood.com/intergrip-p...=google&wv=3.1

Yes, if you want a straight seamless repair. Dont stay in one place, move away by a foot and dont build too much heat in one place.
https://cdn-fsly.yottaa.net/60d0e018...1_p19016_1.jpg

They also have those little round earth magnets ..to hold a panel in place ,for butt welding …no gap

Great Point! I had forgot about the rare earth magnets. I have used these as well.

Keep moving with these so no warping...

Just don’t make the mistake I made when I first started using those strong magnets and attempt to weld too close to them. I swear I had a bad ground or no gas.

Another thing I just thought of with MIG is your shielding gas. Some people will run straight CO2 for more penetration but with sheet metal that won’t help at all. The higher the argon you have in your mix the more it will help keep your sheet metal cool.

More GREAT INFO! This could NOT be more true... Keep moving to different spots and keep it cool !

Thread revival. I ordered a replacement trunk brace for the p-side as the front of the original is toast as is the trunk metal in that area. The rest of the p-side brace is in good shape and the area near the bumper would be a bear to replace without taking car apart. Ok to use only part of the new brace I assume.