[Bronze68]

I've been wanting to post this for some time, as it seems like many questions arise with this subject. I did this frame a couple of years ago but thought perhaps it might be of help to others.

The frame spent its life in Pennsylvania. The car it was under was hit somewhat mildly in the left front years ago. Not enough to warrant work beyond sheet metal, but the horn was out of position, pushed slightly inward and downward. It was also cleaned and painted about 30 years ago and didn't see much weather since then.

I am admittedly a BIG Hellwig frame FX fan since doing this project. However, I'm not going into all the gorry fabrication details when I get to the Hellwig aspect, as there's a lot of threads and videos on that out there already. But, please don't hesitate to ask if you'd like to know more about a specific point in regards to the Hellwig install.

Here are some photos of what I started with, pretty typical:

 

[Bronze68]

The section at the driver's side second from the back body mount hole had a crack running through it. It was shoddily repaired years ago by a poor weld outside.

If you look closely at this next picture, you can see a 1/2" thick steel block welded to the backside of the crack

 

[Bronze68]

The body mount holes were in bad shape, but again, very common for PA cars - rusted very thin, if not through or totally away.

 

[Bronze68]

Needless to say, blasting the frame was imperative, not only in prep for a new coating but more importantly to see all the details and clean as much junk off as possible before welding. I opted to cut out all the bad body mount holes prior to blasting, such that it would allow just a little more accessibility for the blaster inside those immediate areas of the frame.

My plan was to weld in "replacement holes". I bought a kit that UMI sells for just this very application. Basically, they are large, laser-cut washers.

However, some of the holes were rusted thin well beyond the diameter of the UMI pieces, so I actually ended up using hardware store washers to make several of the replacements. The washers were good "blanks" to start with, but I had to machine the center holes open to correct body mount size. I also faced down their thickness a little to get closer to the same gauge as the factory frame.

To get the old holes out of the fame and leave me a perfectly round hole to weld into, I welded a small 1/8" thick by 1/2" wide steel tab across the holes and did my best to determine where the original center was. I then used a hole saw to make the cuts.

As a note, you can do this with a cordless drill......if you have 4.7 days straight to get it done. I found a pneumatic drill to be invaluable for this. As for the hole saw itself, I matched one up to the O.D. of the UMI washers and machined the O.D. of the hardware store washer to a common hole saw size for them.

 

[Bronze68]

So, after the old body mount holes were out, I spent time straightening the bottom of the side C-channels. I apparently didn't take any pictures of the before look, but these side rails were as bad as any I've seen. They should be perfectly flat across the bottom, but these were REALLY bent upward from years in service station lifts, floor jacks, etc.

This is what they SHOULD look like when correct:

To fix these, it's a simple large adjustable wrench. The material moves rather easily. Just have to take your time and work slowly from each end. Don't start in the middle of the bend or it will really draw out the time needed.

 

[Bronze68]

The next step was blasting. Had I known what I was about to find under the junk, I would have done a little more pre-blasting work. The factory welds on this particular frame were really poor - and I know they've never been great, but this one was bad all over. In hindsight, I would have ground them out slightly to allow blast media to get them a little cleaner in preparation for welding downstream. I found holes burned through welds, huge gas pockets leaving little weld metal left, and lots of non-fused areas.

 

[Bronze68]

The rear cross member was really pitted, and I could have easily replaced it, but I deemed it sound enough to keep it, knowing it's not in a high stress area.

 

[Bronze68]

I started to weld in the UMI and home-grown washers. As a note, I TIG welded the entire project. Given that, I spent a lot of time simply waiting for the work to cool, as I didn't want to induce too much heat and the subsequent twisting. An A-body coupe frame is really not that sturdy as-is from the factory.

Basically, I tacked them all in place, and then went back periodically skipping around from one to the other to allow cooling, and completed the welds.


UMI washer:

Home made washer:

I used somewhere around 105 amps and beveled the edges of the washers slightly which gave me full penetration. However, I did go back and weld some holes from the backside, as that amperage was good for only about one thickness of frame material. Where the body mount holes went through the frame half overlaps, obviously the material thickness is doubled. Probably overkill, but I just wouldn't have slept right at night. You can see below where the frame thickness is doubled (on the bottom of the washer) as no penetration is seen from the top-side welding - you can still see the open joint. It was a little tricky to get the TIG torch in there, but I made it work without too much problem.

 

[Bronze68]

My next endeavor on this thing was to improve all the factory welds. This turned out to be quite a lengthy effort. I spent a LOT of time grinding out the factory welds and trying to clean them. Anytime I would hit an old gas pocket or slag, it would obviously blow back at my TIG torch. I think I spent more time re-grinding tungsten electrodes than I did welding...

For this frame, I didn't want to lose the factory look, but I wanted a clean look. I opted to re-weld every inch of factory seam such that I could come back with a grinding disc on my angle grinder and smooth them out.

 

[Bronze68]

I also had to deal with a small hole rusted through the inside of the rear frame hump, just in front of the wheel. For years I had seen the slight hole under the car and thought nothing of it - a factory hole.

Well, not so after blasting. It was indeed a hole rusted right through the middle of the fame wall. I opted to do exploratory surgery and got out the hole saw again.

The wall was rusted thin in more than that local area. I ended up probing with a mirror and flashlight, as well as my finger, and ended up taking out a much large swath of metal.

Welded in a new piece and smoothed out the beads.

 

[Bronze68]

The next phase was the installation of the frame boxing kit. I opted to use Hellwig's kit, as I own a convertible and can attest to the absolute difference in rigidity between those boxed side rails and the open C-channels of a coupe. That trapezoidal cross-section is a little stronger than a square boxed cross-section like those kits offered by ABC Performance and doesn't add a jungle-gym under your car like the Speedtech kit. I remember seeing the numbers Hellwig posted about the strength gain a few years back and was impressed. The Hellwig pieces are a good 1/8" thick (10 gauge), thicker than the factory frame material.

I also like that it added an additional body mount. Couple that with swapping out the typical blank body mount in the middle of the side rails, and you gain 4 additional body mount points.

I thought the Hellwig kit was really easy to install if you have very basic welding knowledge. Their instructions are pretty accurate. The whole key: TAKE YOUR TIME - avoid welding too fast. Getting the new mounting brackets on properly and squared was a bit of a pain, as you need to put the frame back under the body, but, it works out very well in the end. I don't have any pictures of that, but there's plenty of Youtube videos on that out there. Once they are on, I welded a cross piece from one C-channel to the other and began the installation of the main plates. Everything is tacked in place before final welding.

One of the options Hellwig needs you to pick when fabricating is to leave the gradual slope of the top/front C-channel area, or hammer it parallel to the bottom of the C-channel.

I intended to leave it as is, but quickly realized it wasn't as clean of a look when mocking up the plates. However, I was very concerned about hammering the slope out of the top piece (as the instructions tell you), but it turned out to be really simple and fast - like done in a minute fast (GREEN OVAL).

The only problem was that the add-in piece edge went right across a hole in the frame behind the front wheel that I didn't want to close (RED LINE). So, welded on either side of the hole and used a ball-peen hammer to dent the plate and it turned out well.

I had to do some minor grinding/fitment of the plates, but nothing I would call serious. They are purposely long so they can be properly fitted to each frame. A C-clamp worked well to help with eliminating gaps when tacking everything in place.

I did fill in one area just to make a smoother transition.

 

[Bronze68]

The final welding phase of the Hellwig install took a while, simply because I would weld about 3", then stop and not return to that spot until it cooled back to room temperature. Hellwig emphasizes this, and I do too from a good weld practice standpoint. I would weld, and then spend the cooling time dressing the welds as I went.

 

[Cheveezy]

Excellent write up and work!

 

[Bronze68]

One thing I would note is the tie-bar Hellwig tells you to weld in after the new body mounts are tacked, but before you install the side plates. Hellwig says the rails tend to bow outward when you weld. I used 1½" angle iron.

My frame was already measuring ¾" wider than the factory 53" dimension, so I figured I'd pull the rails inward with a strap by ¾" of an inch and then weld the brace in place.

Well, let me tell you: when I cut the welds on the brace, it was quite a "BRRANG". My ¾" only gained me about 1/4" in the end....

So, I guess it's good I pulled it a little instead of just bracing it as it was, but maybe could have pulled it a little more.

 

[Bronze68]

So, it's not totally true that I only used the Hellwig kit. I did actually use ABC's small kit for boxing the rear rails on either side behind the axle hump. These are pretty simple pieces and installed fairly quickly. The only thing I did not like about them was that the access holes for the bumper mount bolts were somewhat small and only round. The holes on the frame as most of us know are oval. I opted to use a die grinder and "ovalize" the holes as best I could before welding them in.

Somehow my ovals didn't get on the same angle, but they did match left to right. Oh well. It's not like people are going to crawl under the car and look specifically for that. The fuel tank obscures that area anyway.

 

[cage2592]

Outstanding work and welds. Super nice. You noted about welding over the original frame welds with a TIG and having to clean the tips. Couldn't agree more and takes up so much time. Yes cleaner looking but my thoughts are they aren't going to get seen most of the time. Plus the paint or powder will fill in a lot as well. I have just resorted to cleaning the old welds, then I only MIG, then clean those up. Basically old welds get MIG, new welds get TIG.

your work is very professional !

Mike

 

[Bronze68]

I had to address a fairly heavily corroded area in one of the front lower control arm mounts. Looks like salt and water rusted it pretty well. I had to take my time but was able to weld it up and dress it back to nominal thickness. Just another area folks should look out for on these frames.

 

[Bronze68]

One other tidbit that I'd heard people talk about was the sway bar mounting holes. At the factory, these holes are basically punched through the frame. The metal that is pushed into the frame is then threaded.

Doesn't feel really sturdy to me.

I debated bothering with this, but figured now was the time, so I bought some flange nuts and did basically the same thing I did with the body mount holes. Note to those who do this: flange nuts are hardened steel. Anneal them before welding or cracking is going to be an issue. Heat them a little beyond cherry-red to an orange-ish color, insulate, and let them slowly cool to room temperature. That will be enough softening to avoid cracking issues.

 

[Bronze68]

So, a few months later the bodywork was commencing on the car, and there were a couple more things to finish off for the frame. The first was to add some reinforcement to the rear of the spring perches.

I planned to use coil-overs on this car and went with Global West's parts. I don't mind UMI or BMR or the other guys, but I really like the del-alum bushings that Global West offers and also because I was going with a Moser rear, and Global West makes lower control arm brackets specifically Moser rear coil-overs. That said, they (like others) employ a bar that spans from one spring perch to the other to help strengthen the top coil-over mounts.

However, this car had a serious rear window leak many years ago that apparently went on for a long time, as it had rusted through the trunk pan and rusted/pitted the top of the frame, and pitted the back of the left spring perch. Not enough to warrant a whole transplant, but enough that I wasn't fully comfortable. I opted to sister some reinforcement plates to the back of the spring perches where 3 new holes will be drilled for the Global West support bar.

I actually (and slowly) welded up a good number of the pits anyway. This is it before I started.

These are the plates that were welded on as reinforcement.

 

[Bronze68]

The next step on the frame was to prepare the cross member. I initially was planning to use the factory cross member and had started to shorten it to work with the Hellwig mounting hardware. But somewhere between the sound of the interior rust pile going from one end to the other and the hole I found that I expanded by punching my finger through, I decided to can that idea.

Instead, I opted to go with a G-force cross member. This car is getting a manually shifted, reverse pattern 4L80, so I used G-force part number RCAEC2-4L80. Figured I'd have to modify it to fit, but that it would be remotely close. NOTE: I chose this part number because it's for a factory convertible or boxed frame.

In the past, I've heard folks call them suspect due to the U-channels they use - "supposedly" they flex...

HA!!!!!! Bull-pucky!!

I can absolutely swear G-force cross members are as solid as a rock and do NOT flex. Not even remotely. Those U-channels are ½" steel. They aren't budging!

Surprisingly, the modification needed was very minimal and simple. When the engine and transmission were mocked up on the frame with the body on top, the tail shaft angle and clearance to the body were perfect with the cross member using the Hellwig cross member brackets. Still a close fit in a couple of spots, but not unreasonable. I should note I'm using Energy Suspension body bushings and motor/transmission mounts. All I had to do was cut about 1¼" off the mounting tabs and re-drill the mounting holes. It was literally that easy. Use the regular transmission mount, not the special one that Energy Suspension offers (I believe it's thinner).