There are a couple of reasons to fill the interior of your car with a rollcage, from meeting safety requirements of a sanctioning body to stiffening up the chassis. We have a '66 Chevelle in the stable that is being built for the street, but with a focus on autocrossing it on weekends. We recently installed a complete G-Street coil over suspension system from Chris Alston's Chassisworks (July 2013 issue). The fully adjustable suspension will allow the car to be quickly set up to run the cones, then dialed back for the ride home.
While we have a great suspension in the car, it is attached to a factory frame, and it has some flex to it. We want the suspension to do all the work instead of the frame moving around with it. So, we are going to stiffen the factory frame the best way we know how, by throwing metal at it. At the end of this story the car will have a boxed frame with solid body mounts and a six-point cage. All this should get the factory chassis as stiff as possible, and net us a safer place to be when we strap on a helmet and get after it.
We have been building this car for a while, and unfortunately there is one thing that goes with this story we didn't photograph, the boxing of the factory frame and adding the cage mounting pads. There are frame-boxing kits out there for the A-body chassis, and are a great complement to a rollcage or high-end suspension. We will find another car and bring you a frame-boxing story, so look for that in a later issue. Back to our main point of all these words, the rollcage.
We ordered up an eight-point cage kit that features 1-5/8 by 0.134-inch wall mild steel tubing, and upgraded it with the optional swing out door kit and removable seat belt bar. This gave us all the components we needed to create our 6-point cage, since we won't need to install the subframe struts that are required for unibody cars. Because this is being built for simple autocross events, we don't really need to conform to any real rules about layout or size, but this cage should be good for 10-seconds and above on the dragstrip. If you are building a car for a specific thing like drag racing or open track stuff, you need to check with that specific sanctioning body for cage requirements. To further stiffen the chassis, we ordered a solid body mount set from ABC Performance. The ABC crew offers a bunch of early Chevelle specific items, and even has a frame boxing kit that we mentioned earlier.
So we had our cage kit from Alston and solid mounts from ABC Performance now we needed one specific tool to add to our collection of necessary items for the job. We already had full selection of magnets, grinders, and an 110v MIG welder. What we needed was a tube notcher. We looked to the king of do-it-yourself, Eastwood, for its Economy Tube Notcher and Hole Saw kit. Once we had all the parts and tools, we gutted the car's interior and got busy.
1. Here's the Chassisworks eight-point rollcage kit. The bars are 1-5⁄8-inch by 0.134 wall mild steel tube. The main hoop, side, rear, and windshield bars are all bent specifically for the Chevelle application. CAC has multiple GM applications, so if you are reading this, then it's a safe bet they have something to fit your project. If they don't you can go through the special order process, and they will use their tools and materials and bend the stuff to your measurements. We upgraded to a removable seat belt bar to go with the swing out door bars that come included with our kit. Rocker tubes, dash bar and helmet bars are available options.
2. Even though the bars are pre-bent, we will still need to do some trimming and notching. We already have a chop saw, grinders, and such, but one thing we didn't have was a clean way to fish mouth, or notch, the pipes. Eastwood's Economy Tube Notcher and Hole Saw kit is made to either mount to a bench or drill press, but you can also clamp it in a vice. It comes with a hole saw kit, and the entire caboodle is under a hundred bucks.
3. Because the cage is going to be welded directly to the frame, we don't want the body moving around, so these little black pucks will help with that. The Solid Performance Body Mounts are CAD designed and CNC-machined from T6061 billet aluminum by ABC Performance. They come in four finishes, from natural to hard-coat anodized, and unlike the factory rubber they will not deflect or degrade over time. We are sure they will not isolate road noise as well as rubber, but for this car we really don't care. The addition of the company's upgraded bolt kit will simplify the install.
4. There is really no secret to swapping out the body mounts. We did one side at a time by first removing all the bolts. Once the entire side was loose we used a jack to separate the body and frame just enough to get the uppers in and out.
5. Once all the uppers were indexed into their respective holes, the lower piece with a nice thick washer and new bolt was threaded in. After we had both sides swapped out we made a few measurements along the rocker and some other key points to make sure the body was sitting squarely on the frame. ABC provides some thin washers that you can use as shims to get it right if it's off. Our frame was squared up after the boxing procedure, so ours lined right up.
6. Also, when our frame was being boxed, we plated the top of the frame at the respective points for the cage. This isn't totally necessary, but it does help make the cage install easier, as the plates are nice and flat compared to the top of the frame. We used a cut off wheel to cut an oversized hole right above our plates. Basically we need holes at the front and rear of the door opening, and two in the trunk for our six pick up points.
7. We used a yardstick and a tape measure to make a few marks on the straight portion of vertical legs that are square with the top. We can use these marks to keep other items square with the horizontal part of the hoop. We also marked the tubes at 42 inches, which is what we had from the top of the frame to about the roof. We left about an inch of clearance for the headliner.
8. The frame is on an angle where the main hoop hits, but we didn't have an angle gauge, so using some cardboard we found our angle and transferred it to the tube. Try and be more prepared than us and get an angle finder. We used the chop saw to buzz off the end of the tube at our mystery angle.
9. The hoop is brought into the car for the first time, and we nailed it! Guess the sun shines on a dog's butt once in a while. Anyway, after a little leaning-it-this-way-and-that-way, we decided to line up the hoop with the angle of the back of the doorjamb and the rear windows. It just looks right, and won't be in the way too much for the rear passengers when the cage is torn down to street use. It ended up being almost a perfect 90-degrees from the rocker panel.
10. Even though the alignment of the rear hoop is visual, we still made sure to measure everything and verify its square.
11. Once we had the hoop measured out we put a few heavy tack welds to hold it in position.
12. The pre-bent sidebars come next, and again we moved it around till it sort of looked right, and held it in place with some fabricating magnets. We are going to try and keep these bars aligned with the roof line and the kick panel, again to keep them as out of the way as possible. We trimmed the lower leg of the side bar bit-by-bit till the upper part was lined up with the roofline.
13. The windshield bar is also pre-bent, and it will dictate how far apart the sidebars can be. It fit pretty well, but we were wishing it was about an inch longer to really push the side bars out. It's a small sacrifice we will accept since we didn't go the custom route.
14. With these components in place, we started marking the tubes for trimming and notching. We did a notch in a scrap piece of the tube just to get an idea of how deep to go with it. Once we had that measurement, which was just shy of an inch, we could factor that into our marks.
15. The Eastwood Notcher and hole saw made quick work of the tubing. Even running the drill nice and slow with plenty of cutting fluid, each cut only took a minute or so.