My Challenger - Cowl Repair Redux

[DPChall]

Hi,

I joined a few weeks ago but am finally getting a newbie message and a few photos out.  This is my 72 Challenger which I bought in 1995.  It is still in a "before" status since it took years to afford a garage that would allow me to disassemble it, obtain tools etc.  It is a 318, all manual car.  I bought a rebuilt, blueprinted and balanced 318 from a racer friend and also added a rebuilt 4spd.  Engine and trans are great; everything else needs work. 

Also added are photos of cowl and firewall where I am teaching myself how to MIG weld - probably the hard way.  I have seen lots of great material her on cowl/firewall repair but would like to know if there is a complete photo essay or faq on this that someone has done.  I have made progress on the large lower holes in the firewall itself; I flanged the edges and am welding patches onto the flanges.  However, I have had a lot of trouble blowing through and making the edges ragged and ugly - even at lower power settings.  I have a Lincoln HandyMig.  I figured out from this forum that the steel is 18 ga, which will help me adjust my settings, but any advice is welcome.  I am working one small piece at a time, using a propane torch to shape steel as needed.  I would like to do a better job with the welds though.  Right now the plan is to fill the gaps and holes with POR-15 epoxy putty as it has been so difficult to deposit weld wire into them without melting everything - including steel that was not thin.

As you can see, I cut away the lower part of the upper cowl under the windshield washer mount.  I am now facing the question of whether to replace the upper cowl - a huge job for a novice?

Thanks for any comments,

Duane

[hpe600rt]

welcome to the site

[Jesus H Chrysler]

Welcome to the site!  Glad to see another 72 getting redone.

I'm no welder but I learned the hard way just as you are now.  I invested in a night course at the local trade school and learned the basics.  It helps a lot!  (hint: the position of the material you're working on is almost as important as your settings!)  I have a Lincoln myself.  My best work comes from using a true M.I.G. process with the shielding gas.  You can work on thinner metal than you can with the flux core stuff.  For best results use a bunch of "tack welds" around the patch you're putting in.  Alternate sides to allow it to cool evenly.  The tack generates localized heat that cools quickly.  If you try to run a bead on sheet metal you'll either burn through or warp it.

2 things I do not recommend is filling the holes with something other than what belongs there (metal) and learning how to weld on your rusty pride and joy!.  I would grab some scrap metal that is close to the thickness you're working on (hit up a body shop for a trashed fender or something).  Cut it up and practice putting it together again and learn how the metal reacts.  That way you're not causing any further damage to the Challenger.

Kudos to you for learning how to do it yourself!

[DPChall]

Thanks for the welcome and very nice '72 ragtop.  What wheels are you running JC?

I am using CO2/Argon mix MIG, not flux core wire.  I am using tack welds, problem may be how long I hold the trigger, not sure.  I would like to take a class but time does not permit, plus many years of inability to act leads to a certain degree of mayhem once one has an arc in one's hand...  I have to admit learning on vertical sheet metal is probably dumb but the ragged repair I am doing is still a lot better than a rusty hole.  And of course using a grinder is fun, except my Craftsman-China special just went up in smoke this weekend.  I think I will do some test welding on my bench for a few hours, good advice - I have a Challenger fender I bought as a replacement for my  driver side fender; turned out its worse than the original so I am using it for patch material.  Do you prefer butt welding or welding a patch onto a flange?  I figured the latter would be easier but now I dunno.  I also have to patch some holes in the roof.

[Sean]

Welcome to the site!  I too am new to welding, having just picked up a Lincoln ProMIG 180.  My previous experience was welding my rotisserie using my buddy's rig and with his coaching watchfull eye - that's it.  The other day I used my rig for the first time to weld a couple plates on a mower deck.  It was down right ugly, but it worked!  I was using the flux core wire that came with the unit.  I'm going to be buying a tank soon so I can get away from flux welding.  I'm also going to pick up some scrap to practice before going live on my car.   

Do you know any welders?  Maybe they could show you a few things to get you jump started.  Also, look on the web for tips and tricks.  Miller Welders has a pretty cool set of training videos on their website which explain how MIG welders work and some basics for welding. 

Good luck!!!

Sean

[hezzel]

Welcome Duane

[DPChall]

Thanks for the welcomes; you all have some very nice cars - obviously a lot of work in them - or going into them.

For Sean, I was thinking about getting a rotisserie for years but was put off by the cost plus I am not planning on doing another car after this one.  However, I have never seen one for sale used.  I have limited time so building one myself seemed to compete with working on the parts of the car I can get to.  My intent is to do the firewall, roof and maybe the trunk floor, which I have removed, and then turn the car over to a local body shop that specializes in Mopars and has a good reputation - I am lucky such a place exists in my area. 

I do have the ability to sandblast it - I have a "PA Blaster" - there is a whole forum for that.   All of this would save $ and build my skills, but if I try to do it all I could be 90 when I finally get to drive it and by then we will all be looking for Edelbrock drop-in electric battery enhancers rather than headers.

That said, if I actually do a good job on this part I may start to change my mind and try and do more.  You can see from my pix what the quality of my weld looks like.  I pounded on it with a hammer and it did not break free, so I must have done something right.  Even as ugly as it is.

I do have an acquaintance who is a retired master mechanic and metal worker who knows welding.  I do not know how much MIG welding he has done but I will check in with him.

I need to take JHC's advice and do some practice welds too.  I have been welding patches onto a flange around the original hole.  In some cases I have used a sheet metal screw to clamp the pieces when I can't get a regular clamp in there, then just welded in the screw and ground it off.  I want to try some butt welds too, but I need to find out if I need a copper backing piece , and if so, how to clamp it in place.  One issue is getting the right setting on the MIG - the setting calls for a wire speed of 6 for 18 ga - seems like that will deposit a lot of steel that I would have to grind off...

[Sean]

DP,
My rotisserie cost me about $550 for the steel, that includes cutting the pieces to length.  I just dropped of the cut sheet when I placed my order and they did all the rest.  All I had to do was weld it together.  To me, it was money well invested.  I don't plan on keeping it after I'm done with my Cuda either.  I was able to get free welding instruction and other help from a buddy of mine and in turn, I'd give him the rotisserie when I'm done.  He would have helped me out anyways, but I'm giving it to him as a gesture of my appeciation for his help.  You could always use it to barter for labor or parts for your car when you are done.

Sean

[Jesus H Chrysler]

Does your welder have a settings chart in it like this:



If so go by the settings for the process you're using.  You can fine tune it for position etc but for the most part the suggested settings will do you fine.  Just remember they settings are based on the metal thickness, and rusty metal is usually thinner than you expect.

[Sean]

Something I learned the other day working on the mower deck, clean metal counts!!!  I was trying to weld to paint & rust covered metal and kept burning through.  As soon as I took some 60 grit sandpaper and cleaned up the area, all went well.

Sean

[jimynick]

Something I learned the other day working on the mower deck, clean metal counts!!!  I was trying to weld to paint & rust covered metal and kept burning through.  As soon as I took some 60 grit sandpaper and cleaned up the area, all went well.
  and having checked for recommended speeds/power settings, the other thing is fit-up. Generally, the thickness of the filler rod/wire is the perfect gap. Give it a zap of perhaps a half second and look at it; if it's burning through, turn down the power until it doesn't and yet still gives a liquified bead and the same goes for the wire feed. Turn it down until the heat and feed come into balance and stitch it together. Trial and error and practice will make you a happier welder. Have fun.

[Super Blue 72]

Hi Duane, welcome to the site! 

I have cowl issues too, water accumulates on the floor when it rains.  Darn mouse house made rot holes in the cowl somewhere! 

Nice thread, I don't know how to weld and would like to learn eventually.  This thread is good to learn from.

Have fun welding!

[DPChall]

Thanks for all input -

I knew I had to develop the right "feel" for this - I can't remember power setting on my welder for 18 ga but I know the wire feed is 6 - seems a little fast.  I want to fill in the areas along the perimeter of the patches that are all chewed up.  It has been difficult to avoid melting.

Also, I cleaned everything to bright steel.  I cut the holes out beyond the rust, except for the curved interior of the cowl funnel area.  That is very thing and corroded but surprising took a weld.  It has small holes that will need fill with POR-15 epoxy putty if I am not going to cut it out and totally replace it.  That seems a bid extreme.  I am hoping to avoid replacing the upper cowl, but the fabrication of the parts I cut out will be "interesting"...

D

[usraptr]

Welcome and congrats on the fabrication and welding.  Good job. 

[Milkmann]

Congrats on tackling a big job!!

You've been given good advice with "practice". That's the only way. When I was younger, I spent many hours welding scrap metal together. I'm still not very good at it, but having a MIG welder makes welding sheet metal much easier. I have the best luck welding in short bursts, almost like a tack weld, and give it a few seconds to cool before the next burst. Takes longer, but I have less burn-throughs. I envy the guys who can lay a smooth bead on light sheet metal.

I friend of mine says his Dad told him a good welder should be able to weld a Copenhagen can, he kept at it until he could(this is back when Copenhagen cans were made out of metal).