Tips for filling in holes from bumper

[zsteelman]

I am in the process of shaving all the holes in the rear of my 77. I have already removed all of the components and now I am ready to start filling in the small holes and larger pieces.

 

 

The holes circled in red are the ones that I am having problems with. The ones from the spotwelds from the bumper lip are not accessble from the rear as it is inside the frame rail. The ones on the right where the tow hooks were are not accessable from behind either. I am trying to weld these in but my welder keeps blowing holes through the sheetmetal at the moment. I would normally take a piece of copper from behind to prevent as much blowthrough and let the weld pool but cannot in this instance. I am using a crappy HF welder with only a Max/Min and wirefeed settings. It is a flux core model ( I know, but it's all I could afford at the time and has worked well on fabrication parts so far). Any tips from people out there on how I can fill these holes in or atleast how to reduce the heat on my welds? I was told that I could put out more filler line than normal to increase the resistance and that it should cool the weld down some. These are not structural welds so I am fine with a topheavy weld I just want something that is going to hold my body filler in.

 

 

Thanks,

Zach

[240zBoy]

Here's an idea that I have used with smaller holes and might be worth a try... Put painters tape on backside of bumper and then apply jbweld to the front. Smooth and apply just like bondo. Wait until its try and painters tape will come right off the back. Grind till smooth.

[zsteelman]

I had through about that but the problem is that I can't get to the back of the holes because they are inside the frame rail in the back. I have also thought about rigging up a way to hold the jb weld into those holes as I think that will be the easiest way for now. With the larger holes from the bumper supports I can get behind them with a copper piece and stop the burnthrough. Thanks for the tips.

[goodoldjam]

HF welder will do the job. I'm doing a patch with a HF welder right now, it doesn't do a great job but it does work. Basically you do a quick tap and let off and do another before if cools and just repeat. That's the only way to get good heat control with 4 settings. I like running it hot, like Max 1 wire speed 3.5. Then i just do that tap method so I don't blow through.

It's a pain to do and slow but I haven't found a better way, it's either to cold or to hot.

Try to build off the initial weld and move to the other side, it's hard to explain but you can do it.

JB weld could be a decent option also.

Long strand fiberglass filler may also be a option.

Edited August 6, 2010 by goodoldjam

[240zBoy]

I say you put painter tape in through the holes though or even ball up painters tape and push it through until it creates a backing on the other side. You won't be able to get the tape out but its not like it will harm any thing.

[zsteelman]

Thanks for all the tips guys, I finally got my welder to work decently enough to patch one of the holes, it sure isn't pretty but it is going to be skimmed with bondo anyway before smoothing. For the tiny holes I decided to go ahead and use JB weld as that seemed to be the simplest for now but we will see, I may end up throwing in some very tiny pieces of metal instead because the tape is having hard time.

 

I will post some pics up later tonight with my progress. For the welder, I just couldn't pass up 89$ for a welder with a 20% off coupon to boot. It works great for doing bracketry and other small things but these sheetmetal does not look very pretty.

 

To keep from having burnthrough I grabbed an old Heatsink off of a motherboard sitting in the garage and am using it as a copper spoon. Simply grabbed a clamp and positioned it behind the panel to hold the welds for me.

[zsteelman]

Well I finally got out there and welded up the majority of the holes that can not be filled with fiberglass bondo filler.

 

 

These welds aren't perfect but they hold and will be good enough for now. This is going to be a track car not a show car, so it is what it is.

 

 

 

Made the patch panels out of the wrecked front valance pieces.

 

This is what I used as a copper spoon replacement, it is a computer heatsink held from behind with a clamp. Helps keep welds from blowing through. It is solid aluminum and will not stick to the welds.

 

 

Now I need to patch up the mounts for the tow hooks but I am thinking about maybe leaving them incase I ever want to add some on for the track. Anyone NOT shaved it when they shaved their rear before? I tried searching for them but the majority of the posts shave everything entirely.

[emeraldlion]

I was planning on not filling the holes for the tow hook or the bumper connector on the side fender and just putting in chromed alan headed bolts as place holders. It isn't the smoothest but it doesn't look bad. Did it in a volkswagen I had will try to find the picture. I wanted to do this so if I ever sold it the next owner would have choice of putting a bumper on if wanted.

[zsteelman]

Yea I just wish that the holes were symetrical across both sides.

[240zBoy]

Another thing. I recently was looking into buying that 110 flux welder from HF that you have and from what I heard by buying lincoln welding wire the results are a million times better. The welding wire it comes with splatters more than Yao Ming pissing in a toilet. To add to that maybe try a different size wire.

[zsteelman]

Yea the HF wire is HORRIBLE, I did pick up some Lincoln wire but this HF wire is almost up so I figured I would finish it off for these small things and save the good wire for my floorpans and rockerpanel patches. I plan on finishing up the shave today hopefully, gonna be a few days before I get my filler in though so can't get my completed look just yet.

[zsteelman]

Well finally got all but two holes welded up.

 

 

I'm finally getting the settings figured out for this welder I think. Works alot easier when doing lap welds instead of butt welds as the blowthrough doesn't become as big of a problem.

 

http://s24.photobucket.com/albums/c9/zachissak/280z/

 

Here is my entire build pictures if anyone wants to see it. I try and update it each day that I work on it

[240zBoy]

Nice job on getting the welding down. The rear is gonna look really good when ya finish it up. I am really motivated to go pick up that little welder now. I even got a 20% percent off coupon today so that might have done it for me. Now to convince pops to let me keep it in his garage haha. He thinks there super dangerous even though I borrowed his friends mig and tank last summer lol.

[goodoldjam]

The best weld I got out of the little HF welder, was actually when I welded on a wastegate adapter to the cast steel turbo manifold.

I should have taken a picture of it because I'll probably never see that again.

Sheet metal doesn't weld to well, you want it to penetrate so you can grind it smooth. Then you have to deal with it blowing through. I have become pretty creative with how I weld sheet metal.

I've ran about 8lbs of wire through the welder so far and there are some issues with it.

You have little heat control and it doesn't feed smoothly even if you have it hot enough. Probably would be a worthwhile investment to run gas with it, if you get a model setup for it.

I figure it's a backyard hobby welder, works good for exhaust.

And the HF wire was very bad...It's like welding with normal wire with no gas.

Edited August 8, 2010 by goodoldjam

[240zBoy]

Exactly my thinking. I want to fab up my own exhaust using summit piping and mendrel bends. Would cost me only around $100 in material. And to make my own rear strut brace just like PDKFabrications because they won't put it in production and that is $150 online w/o shipping and would cost ~$50 in material. I see that as over $400 in savings and would pay for the welder easily. But then again I am really trying to get this done quickly and that would take a lot of time.... Guess we'll see

[zsteelman]

Nah it doesn't take that long. Honestly you could probably simply pick up a strutbar for another car and modify it (slice and dice) to fit in the Z. This welder has been one of my favorite tools I have ever purchased. It did wonders for helping me create mounting brackets, welding nuts onto the back of panels for threading, etc.

 

Just go get one, you won't regret it.

[zsteelman]

Hey guys, just wanted to give everyone an update on the progress so far. After figuring out the welder settings for this sheetmetal I was able to weld in panels for all of the low spots.

 

After that I picked up some long hair fiberglass reinforced body filler to grip the welds alittle better.

 

First coat

 

Sanded down first layer and highlighted low points to determine second layer

 

Primer guide coat to check lower spots after second layer.

 

Final stages of long hair filler, I have to pick up some normal filler tommorrow to fill the smaller bumps.

 

I also need to look into buying an orbital sander as blocking SUCKS on fiberglass filler.

[emeraldlion]

You're telling me. Half my 62 vw van is bondoglass and bondohair, lol. That is going to be one sexy behind in no time. I'm hoping mine will be as presentable in the next couple of months. I'm currently in the process of removing my duckbill/bumper lip.

[zsteelman]

Yea after seeing some of the cars on here with shaved rears it made me do it instantly.

 

I am shaving all of the marker lights soon as I get this part finished up.

 

I need to get around to painting the interior floors soon as well so I can start putting it back together.