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Discussion Starter #1
I gouged out the holes down low on the quarterpanel and sanded pretty good inside and out. Should I primer? does the bondo go on the inside or the outside? etc.
 

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Bondo on outside IF you can get it to fill the holes.... Proper way is to replace the church going metal, and primer yes on BOTH sides if can be reached. Bet yet a rust INHIBITOR on the inside, or encapsulater would be best. You COULD mig the holes closed first (better than just covering) then grind/plastic finish with primer if patch panel replacement is out . M2C
 

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I would use All-Metal or Bondo Metal Fill.
It is a lot harder and stronger than regular bondo.

Eastwood makes an Internal Frame Coating with a flexible spray tubing to get to the backside of the holes.
 

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forget the all metal n other metal type fillers there junk,mig weld in new metal if possible. ive seen guys jb weld metal over the holes if you feather the metal to a knife edge then fill its almost impossible to detect after primer use epoxy primer,this aint the place for rattle cans if possible.
 

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Discussion Starter #5 (Edited)
I can't weld. Plus, its pretty invisible down there, I'll be using a rattle can finish.
Hey, MrOld, I get it, "church-going," LOL. Good idea about the rust inhibitor, thx. You coulda had this car, I bought it from a guy in Dumas.
 

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cut that out and weld new metal in....bondo will just crack and fall out if you try to fill holes with it
 

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as strongly as I can possibly suggest it, METALPREP FIRST.

Ace hardware sells Ospho (phosphoric acid) brush that crap on after getting all the loose rust off, it turns the metal kinda black. anything that it turns black is iron phosphate, and even if you didnt see it before it WAS iron oxide(rust) before the acid hit it. Self etching primers kinda take care of this but not as well as a brushing or two with Ospho. Ive piddled around with bodywork since '80, still wont claim to know what I'm doing at all- but on advice of someone that 'knew', ospho soon became my best friend at stopping rust. even microscopic rust can grow, blister paint up, but treating with ospho first stops it as dead as rust gets...

cutting out/welding is the only way, I still ospho even brand new metal before priming, havent seen even spraycan paint blister up...but spraycan paint is soft, will fade and weather away...underbody stuff, consider using rollon bedliner to seal it up, help stoneproof- just be certain you keep the lowest point open for drainage, macs, other resto places sell the rubber drains that let stuff out while keeping spray off the wheels from getting inside.

something that might sound really stupid, but I truly believe works:
ospho inside and out, por-15 paint inside, while still wet, push por15 saturated strips of paper towel into the wet paint, brush out all the air pockets you can... its messy to do, but dries hard as fiberglass, and wont rust. I had one spot under the rear seats of our 65, had a reinforcement thing under, woulda been hard to weld in and be able to coat- so i dug it out, slopped POR15 in the hole, and over, put the papertowel over, brushed it out- so far no problems. if done from inside the trunk, it might fill the void enough to fill over from the outside pretty easily, definitely not good as metal, but it would both seal the rust and give enough thickness to stiffen the thin areas...bondo/paint wont stick to POR, would need sanded so the only POR on the outside would be the actual holes themselves, then re-ospho/prime/skimcoat with any filler and block it down. you could POR saturate 'glass cloth or mat, but I couldnt get it to lie smooth...papertowel sounds silly, but once its saturated its really easy to stretch so it lies flat and dries very solid...if strengths a concern, add more layers or even a layer of glass behind, but I really dont think it would be needed. if you buy POR, dont open the can- get some clear hardware store tubing about the size of your biggest phillips screwdriver, pierce 2 holes in the lid, push a loop of the tubing in to seal the holes... pull one end out, pour a little at a time into a disposable plastic container, plug the can immediately. POR if opened will jell up in a few hours if exposed to humid air- using the tubing Ive had a can useable a year or more later. dont clean the containers, leave the brush in it, next day pull brush/paint chunk out and you can reuse the cup :) dont get it on your skin, it dont come off. and dont brush POR15 over paint, it wont stick to paint.
 

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Cut it out and weld in a new piece of metal, otherwise it will be like a famous person from CA said "I'll be back". No kind of filler (bondo) will stop rust, and you can put any kind of rust converter on it you want and it will still come back.
 

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I can't weld. Plus, its pretty invisible down there, I'll be using a rattle can finish.
Hey, MrOld, I get it, "church-going," LOL. Good idea about the rust inhibitor, thx. You coulda had this car, I bought it from a guy in Dumas.
If you can't weld you could glue the repair panel on. You really need to cut the rust out and use new metal to repair it. Using bondo would be temp fix IMO. And usually bubbles or falls out.

Using panel adhesive is pretty quick and easy. Also agree with Ford4v429 with coating the inside of the repair with POR.

Glueing new metal in and coating inside with POR would give you a lasting repair

Lou
 

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if you buy POR, dont open the can- get some clear hardware store tubing about the size of your biggest phillips screwdriver, pierce 2 holes in the lid, push a loop of the tubing in to seal the holes... pull one end out, pour a little at a time into a disposable plastic container, plug the can immediately. POR if opened will jell up in a few hours if exposed to humid air- using the tubing Ive had a can useable a year or more later. dont clean the containers, leave the brush in it, next day pull brush/paint chunk out and you can reuse the cup :) dont get it on your skin, it dont come off. and dont brush POR15 over paint, it wont stick to paint.
Cool idea with the tubing. I use a plastic syringe, I carefully remove lid and stir without getting POR in the rim then use plastic syringe to remove POR from can and put in mixing cup. Immediately cover can with Saran wrap and replace lid. Works pretty well for me. Haven't had a can go bad since started doing it this way.
The POR doesn't stick to the plastic syringe, just let it dry and it comes off so you can use it again and again.

Lou
 

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putter,
these guys who say replace metal with metal (weld) are right. If you don't then someone else later will have too. Where are you located, maybe I know someone who can weld for you. If not then a good starter MIG welder is about 500 bucks and lots of video on how to weld. If nothing else, an old saying, you are not a real man until you have cut metal with fire, so yo gotta do it. LOL
 

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Discussion Starter #14 (Edited)
I think I got the holes plugged up. Took three layers of (year-old) Bondo, not sure it is real tight in the holes, obviously I am a klutz at it (pic1).

For future searchers, let me suggest this. From the inside, lay down a layer of fiberglass, covering all the holes. Stab in the resin, enough to drip through the holes. Then immediately from outside mix and lay on the Bondo. It *should* grab on to the resin as it sets up and should make a tight repair. Ford4V would do something similar but with POR, which is not that easy to find locally.

I tried this using Bondo on the inside but it was hard to spread aqnd also set up too fast. Now I have chunks of Bondo in there instead of a smooth piece of fiberglass. live and learn I guess!

I primed it, sanded and used acetone as prepaint. Don't do that, it dissolves the primer. Now I don't like to mix paints (laquer over enamel? or vicer versa? etc), I use Duplicolor Perfect Match for both paint and clear coat. if you want glossy, you have to hold the can 4" away or the paint will dry out in the air on the way to the car. Spray fast to avoid runs but spray close. A little rubbing compound to rub away the overspray. Then clear, again close up. Rubbing compound for the overspray followed by polish on an electric polisher will make it shine. I'll wait wax it next time I wax the car.

I am happy the way it turned out. Close up and from ground level, the bondo work was obviously not so good (pic2) but compared to the plethora of rust bubbles that was there, it looks great especially from five feet away (pic3)
 

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