For many people, modifying the interior of their Chevelle is one of the most difficult parts of the car buildup to plan. There are quite a few areas that you may want to upgrade, but making changes to the classic lines and details of the interior without considering the overall theme of the car can quickly disrupt the design and style of the car. The end result can be a finished product you’re not happy with. As with the overall exterior styling of your car, you have to plan and envision what you want the theme of your interior to be in addition to functional upgrades.
This Tech Tip is From the Full Book “CHEVELLE PERFORMANCE PROJECTS: 1964-1972“. For a comprehensive guide on this entire subject you can visit this link:
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There are four basic interior areas that you want to consider upgrading for better performance: seating (including safety belts), safety cage, dash, and sound deadening. Installing a cage is the most involved and makes the biggest change in the interior. All of the other projects are manageable in a day or a weekend. Before you dive into these or any other interior upgrades, though, think through the style you’re trying to achieve with your car in addition to the specific performance upgrades you would like.
Chevelles were family cars when originally produced, and seat technology was far from a science. A wire frame, some springs, foam and other stuffing, and upholstery were all that was needed. Today, I generally want a seat that offers control (keeping you in place as you turn corners) and comfort. There are also safety concerns. A performance or racing seat is built to keep you in place, even during an impact, and almost all of them are designed to work with 5-point safety harnesses.
Speaking of safety harnesses, the next time you get into your Chevelle and click the 40-plus-year-old seat belt around your waist, think seriously about how much you trust a nylon strap of that age. If you do any competition driving with the vehicle, you also want to think about the considerable safety added with shoulder belts, keeping your torso away from the steering wheel and your head away from the windshield in a crash. There’s a reason all new cars come with three-point seat belts and that five-point safety harnesses are required in most pro-level competition cars.
There are some realities to deal with when you add a cage to your car. Most cages make getting in and out of a car a bit challenging, and they generally make the back seat impossible for anyone to access except children and extremely limber adults. But a cage provides crucial safety in a high-speed crash or rollover (both of which are a real possibility if you plan to drag race or road race your Chevelle) and it provides a significant improvement in chassis stiffness, which is a performance advantage for any type of racing.
Most cages compromise the interior, but there are a few things you can do to minimize this. One thing you can do is make removable or swing-out door bars. This makes getting in and out of the car much easier for front-seat passengers. And it’s possible to do a swing-out bar in a way that still meets NHRA rules. While NHRA rules don’t apply for autocrosses and road courses, these rules are a very sound guideline for building a safety cage for most types of racing.
Another option that makes a cage extremely livable is a bolt-in system called TigerCage from Ridetech. The tubing in the TigerCage is all stainless steel, and the cage bolts to key chassis points and uses clamps to attach tubing within the system.
Most people don’t want to replace the entire dash, but would like some space for serious performance gauges. Depending on how you want to use your car, you may also want room for a new-style radio, or combination radio and navigation system, as well as controls for an aftermarket air conditioning system.
The key here is to add modern performance equipment without looking like you just started hacking and adding things to the original dash. If you’re skilled at custom fabrication, you can modify your existing dash, or build an insert from scratch. For the rest of us, there are a few popular aftermarket options that make installing large gauges and modern conveniences a bolt-in exercise.
There is another option for 1966– 1967 Chevelles from ABC Performance. This dash bolts in, replacing your entire dash shell and opening up the gauge area, allowing you to fit a 5-inch-diameter speedometer and tachometer. Even though the dash bolts in place, each one is custom-built, so you can specify the radio, vents, air conditioning controls, and switches you want mounted and in what location.
Sound deadening doesn’t make your car any faster or handle any better; in fact, it does just the opposite because you are adding a fair amount of weight to your car. But the improvement in sound quality helps you enjoy every minute that you spend in your Chevelle.
Road noise and exhaust sound vibrates the floorpans, doors, and quarter panels when your car is running and driving down the road. Dynamat, Eastwood, and Hushmat make material in sheets that you can cut and stick to these surfaces. It deadens the vibration at the sheet metal, removing the most annoying noise from the drive and reducing the overall sound level. If you cover the inside of doors and quarter panels, as well as the roof, you can have doors that sound like those on a Mercedes when you shut them, and create an interior that’s downright enjoyable in traffic or cruising down the highway for hours on end.
Whether to cage your Chevelle or not is a big decision. There’s no question that a roll cage makes a significant difference in chassis stiffness, which contributes to better drag-strip launches and much better handling, and improved safety is a given. However, installing a cage is a big undertaking and compromises the ease of getting in and out of the car, as well as almost entirely cutting off access to the backseat. I worked with Tony Grzelakowski at ABC Performance on the design and installation of this cage in an early Chevelle.
Project 1: Roll Cage Installation
Step-1: Replace Body Bushings
For strength and integrity, the right way to install a cage in a Chevelle is to weld it directly to the frame. So the first step is to actually replace the body bushings. Once the cage is welded in place, they are nearly impossible to change. If you install a set of ABC Performance solid body bushings, they should never wear out and they provide increased chassis stiffness. The bushings are CNC-cut from T6061 billet aluminum. They have the proper steps machined to seat in the various frame and body holes perfectly.
Step-2: Take Measurements
Building a custom cage is part science and part art. There are measurements to be taken, angles to work with, and metal to be bent. But you have to make sure it looks right as well. You have to decide how much cage you want or need. If you will be drag racing, there are specific NHRA rules concerning this, and you should reference the rulebook to make sure you comply with the current regulations. This cage is as much for chassis stiffness as safety, so it is a 10-point cage, but four of those points are under the hood. The interior looks like a traditional six-point cage. The first tube you bend is the main hoop that mounts just behind the front seats. It’s ideal to locate this a few inches behind the driver’s head. The bar will be hidden behind the junction of the door and quarter windows, so it is as stealthy as possible. Use a plumb bob to ensure that the line you are envisioning is straight up and down.
Step-3: Bend Roll Cage Tubes
The bends in a roll cage are made with a tubing bender. The arc of the bend depends on the specific dies that you use with your bender. You have to factor these bends into your calculations and recheck the dimensions after you’ve added in the radius. Tony uses long straightedge to map out each piece of the roll cage on the floor before cutting or bending the tube. Or, use metal electric conduit to test the shape and length of each piece before bending up a section of expensive roll cage tubing. There are two types of steel tubing you can use for roll bars and roll cages. The less-expensive material is drawn-over-mandrel (DOM) mild steel. NHRA requires all DOM tubing to have a wall thickness of .118 inch. Chrome-moly is more expensive but much lighter, and the required wall thickness varies from .049 to .83 inch, depending on where the tubing is located in the cage. A DOM cage can be MIG-welded, while chrome-moly requires TIG welding.
Tony uses a JD Squared bender, which is an industry standard. A selection of dies is available for the various diameter tubes. Slip the tubing in place, and then manually bend the tubing and ratchet the bender until the angle of the desired bend is achieved. (JD Squared also offers hydraulic rams to work with the bender to take the manual part out of this process.) There are a couple of things to watch with any bender. One is where the bend actually starts in the bender. Make a test 90-degree bend with each size of tubing you use in your cage. Mark where it sits in the bender, and then measure from this point to where the bend actually starts when you pull the tube out after bending it. The other nuance is spring-back. The steel springs back a little bit after you release the pressure. To get a 90-degree bend, you may have to go to 95 degrees. It’s very difficult to undo a bit of the bend, so start by going a few degrees past your mark and then increase it 2 to 3 degrees at a time until you get the desired angle.
Step-4: Cut Roll Cage Tubes
You can use a band saw or a chop saw to cut the tubing. With either tool, you need to clamp the tube firmly before making the cut. Several of the cuts require an angle like the one on this main hoop to match the angle of the top of the frame rail. Make the first cut about 2 inches longer than what you think it needs to be and then work toward the final length. You can’t put material back on the tube, so it’s very important not to cut too much.
Step-5: Trial Fit Main Hoop
This is the main hoop after a few trims and trial fits. It’s lining up well with the design that Tony measured and sketched on the shop floor. It’s easiest to start in the center of the tube and work toward the ends, finishing one side at a time. Remember to always make the bends in a symmetrical pattern, so that the bend’s start and stop points are the same on each side.
It’s easiest to build a cage with the headliner removed from the car, but it can be done with the headliner in place. You need to use a metal shield to protect the headliner when welding. If the car does not have a headliner, you need to know where the headliner will sit. Tony used masking tape pulled taut between two headliner bows to mimic the location of the headliner. Also make sure you’re leaving enough room to install window trim, the dome light, rearview mirror mount, and anything else that may be blocked if you get the tubing too close to the roof.
Step-6: Tack Weld Main Hoop in Place
After several trial fitments and trimming, you are ready to tack-weld the main hoop in place. Since all Chevelles are full-frame cars, you need to cut access holes through the floor and weld the cage directly to the frame. Tony trimmed this hole large enough to weld all the way around the tube when it’s time to do the final welding. For now, double-check your measurements front to rear, and side to side, and then tack-weld the main hoop in place.
Step-7: Bend Rear Bars
Once the main hoop is in place, you can either do the rear down bars or the front bars. The front bars are the most difficult, so I prefer to do the rear bars first. Using a long piece of welding rod or electrical conduit, bend the basic shape of one of the tubes. You want to follow the roof and headliner shape, leaving enough room at the rear window for trim installation, and pass through the package tray and trunk floor to contact the frame. These bars triangulate the main hoop, giving it stability in a rollover, and also tie in the rear section of the frame where the springs and shocks mount, providing very good suspension stability.
Step-8: Cut Holes in Floor for Rear Bars
You need to cut holes through the floor, and probably through the package tray, too, depending on whether someone has already cut holes for 6 x 9-inch speakers. This car has a coil-over suspension tubular crossmember to tie into. If your rear suspension is the stock style, your holes and bars need to be farther outboard to hit the top of the frame rails.
Step-9: Fit Rear Roll Bars
Transfer the shape to a piece of tubing. For these tubes, you can use the welding rod you bent as a guide right over the tubing in the bender. I recommend getting one of these bars completely done before starting on the other. At this point, the lower end of the bar is still a couple inches too long, and you need to cut about 6 inches from the top. This end has a fish mouth, making the cutting of the bar a little trickier.
Step-10: Create a Fish Mouth
Before you trim the lower end of the bar, you need to trim the top end that meets the main hoop. The trick here is to cut the tubing long enough so that the top and bottom of the tube fits over the radius of the main-hoop tube. Using a tubing notcher, cut the top end of the rear down bar in a fish-mouth shape. This fits over the main hoop and allows the tube to be welded all the way around. You can angle the way the bar is held in the fixture to recreate the angle that the bar fits against the hoop in the car. Ours is pretty close to 90 degrees. It takes a lot of care to get this cut right, and to not remove more material than needed. Once this end is done and fits the main hoop well, fit the other end to the frame rail.
Step-11: Clean Up Tube Ends
Finish all tubing ends with an abrasive disc. This cage is chrome-moly and TIG-welded, which requires extremely tight fitment between the tubes. You can use the abrasive disc to fine-tune the gaps, removing high spots so that the tubes fit very tightly together. Patience and double- or triple-checking your measurements and work along the way avoids frustration and wasted tubing. Tack the rear down bars in place to add stability to the main hoop before you start on the front section of the cage. This keeps the main hoop from moving and lets you fit the front bars perfectly.
Step-12: Choose Location of Front Tubes
The front bars in a cage present a number of choices. First is whether to pass the bar through the dash or in front of it. Some people don’t want to cut holes in the dash, and it’s a lot of work to get the tubes to go through the dash and around and through everything necessary to hide the rest of the cage inside the dash. However, going through the dash allows you to hide the bars behind the A-pillars and make it easier to get in and out of the car by having the bars connect to the frame farther forward, out of the door opening. It’s a personal choice, and there isn’t a right or wrong way to do it. If you go through the dash, you need to determine where the holes should be cut, considering the angle of the A-pillars and the transition to the frame rails.
Step-13: Cut Holes for Front Tubes
Use a cut-off wheel to start the hole, and then use a rotary file to turn the square hole into an oval. Because of the curve of the dash, this hole is much longer than it is wide. And you probably need to trim the hole several times as you fit the bar. Keep the hole as tight to the bar as possible if you plan on welding them together when you’re finished. If you don’t want to weld them, leave a 1/4-inch gap all the way around the bar to allow for vibration and movement. The dash pad can cover the transition for a finished look.
Step-14: Choose Front Bar Design
There are also two methods of constructing the front part of the cage. One way is to use two bars that run from the main hoop down to the frame rails on each side. A third bar is welded in place at the top of the windshield to connect these two tubes together. The other way to do the front section is to create a halo bar that starts at the main hoop, runs across the top of the windshield, and then connects to the opposite side of the main hoop. Down bars then connect the halo to the frame rails along the A-pillars. Because of the radius of the 90-degree bends at the windshield, it’s difficult to get a halo-style bar to fit as tightly to the car, but it’s generally easier to create the front half of the cage with the halo style. A super-tight fit makes the cage nearly invisible when finished. Tony worked three bends into this down bar, all in different planes, to get it to follow the roof and A-pillar lines perfectly.
Step-15: Fit Front Tubes to Cage
For the tight fit of a properly finished fish mouth, each tube must be hand-fit in the exact location that the bars intersect. Moving this bar up 2 inches requires a different angle on the fish mouth, and the tubing diameter changes slightly through the curve. Mark everything, measure at least twice, and trim slowly until you get the perfect fit.
Before tacking the front down bars in place, make sure you’ve left enough room to get the kick panels and any other trim in place. Tony also trimmed away the bottom part of the dash mount. Weld the tube to the dash mount, reinforcing this mount, and also eliminating the possibility of a squeak. A cage vibrates quite a bit as the car drives down the road. Any place that a tube comes close to metal, either attach it to the metal (which is usually best for added strength and to reduce overall cage vibration) or make sure there is enough clearance so the two can’t touch. There are few things more irritating or harder to find than a metal-to-metal squeak when the car is finished.
Step-16: Fit Front Tubes to Cage (Continued)
With one A-pillar bar finished, Tony transferred the key measurement points to the second bar. A couple of precautions when you do this: First, most cars are not perfectly symmetrical, so you still need to double-check the measurements and angles as you work. Second, you need to do any left-to-right angles in the opposite direction. For example, these bars have a slight bend outward along the top of the side-window openings to line up for their drop through the dash. This bend is in opposite directions on the left and right to create the same effect on both sides of the car.
With the A-pillar down bars tacked in place, Tony worked on the top windshield bar. This bar is pretty tricky, because it has a fish mouth on both ends. Tony also put a slight bend in the center of the bar to help it follow the shape of the windshield opening. Use quick-release clamps to keep the bar from sliding down as you trial-fit it. Another choice you have to make is how far forward and high this bar sits. Will you have sun visors? Was your factory rearview mirror attached to the roof pane instead of glued on the windshield? Make sure you leave room for the components you want to keep.
When you have the bar fitting perfectly, mark a spot on one of the A-pillar down bars that are covered by the windshield bar. Drill a 1/8-inch hole in the tube. You need to do this anywhere that a tube is closed on both ends so that the gas and pressure trapped in the tubing during final welding can escape. Typically, you can drill one hole here, one where the seat brace connects to the driver’s side of the main hoop, and where all four of the front and rear down bars connect to the main hoop. Then drill one hole near the base of one side of the main hoop. This should provide a pathway for all trapped gas and pressure, but look at your cage and trace the path for each tube.
Step-17: Install Engine Bay Down Tubes
Next, you craft engine bay down bars. These help strengthen the front section of the frame and are helpful for chassis rigidity. It’s extremely helpful to have all of your under-the-hood components, such as brake and clutch master cylinders, fuse box, radiator, and so on, installed for mock-up when you do. Tony strongly recommends to add a stringer that connects this down bar to the frame behind the upper A-arm mount to straddle the key suspension mounting locations.
Step-18: Install Seat Brace Tube
The seat brace in this car was welded straight between the legs of the main hoop. This bar must be within 4 inches of the top of the driver’s shoulders for proper safety harness location. The door bars were the last bars built for this cage. The NHRA rulebook says that the door bars must pass the driver at a point midway between the shoulder and the elbow. The easiest way to do this is to sit in the seat with your hands on the steering wheel at the 9 and 3 o’clock positions and have someone measure the position of your upper arm. You can add some shape to allow the door bar to clear the door-mounted arm rest. Also make sure that you have the seats in the car that you plan on using. Some seats are wider than others and can interfere with the door bars.
Step-19: Weld All Roll Cage Tubes
TIG welding is a slow process, and the final steps of welding the cage can take quite a while. A variety of TIG torches can make welding in the tight locations a lot easier. Do not grind or sand any of the welds. If you need to have the chassis certified at some point, it will be rejected if any of the welds have been ground. Here, the finished engine bay down bar has the rear extension in place.
Project 2: Interior Installation
Step-1: Remove Old Dash
For 1966–1967 Chevelles, you can fit performance 5-inch gauges with a bolt-in dash replacement from ABC Performance. It retains the classic shape of the original dash, but allows you to fit the gauges you want, as well as a single- or double-DIN radio, aftermarket air-conditioning controls and vents, etc. The first step is to remove your old dash. With the steering column removed, there are four bolts at the bottom corners of the dash and nine screws holding the dash in place. You can leave the dash assembled and disconnect the wiring once it is in this position.
Step-2: Cut Out Dash for Gauges
Tony at ABC starts with an original core. He finds one that has had the radio holes cut out or is otherwise less desirable to someone restoring a Chevelle. To make room for the large-diameter gauges, ABC Performance cuts out the section of the dash that held the ignition, headlight, and windshield wiper switches.
Step-3: Weld Dash Sheet Metal
New sheet metal is TIG-welded in place to create a tall surface all the way across the dashboard. There are about 15 hours of metal fabrication invested in each ABC Performance dash.
Step-4: Dash Options
The top example of an ABC Performance dash retains the factory ashtray, heater controls, and glove box; these holes have all been filled in the lower example. The upper one has the headlight, ignition, and windshield wiper switches mounted on the left and right sides of the steering column; the lower one is completely smooth, and these switches can be mounted in the gauge panel, a center console, or integrated into the steering column. Whatever systems you are interested in having in your car can be added, and whatever you don’t want can be removed. The dash can be shipped to you in a rough finish or completely done.
Step-5: Inspect Gauges
ABC Performance has several gauge inserts that accommodate a variety of gauge, radio, and air-conditioning vent configurations. It also offers a blank template (shown) that can be customized. This dash has a rack of Stewart Warner gauges for a classic old-style race car look. The electronic speedometer and tachometer are 5 inches in diameter, while the fuel, oil pressure, water temperature, and oil temperature gauges, as well as the volt meter, are 21⁄8 inches in diameter. A push-button ignition switch and toggle switches from Painless Performance are also mounted in the panel, further adding to the race car style.
Step-6: Install Gauges in Dash
TJ Grzelakowski at ABC Performance laid out the gauges and switches in a pattern that looks good, cut the holes in the panel, and installed the gauges and switches. The gauges slide in through the front of the panel and are held in place with clamps that bolt to the back of the gauges. It is easiest to build a wiring harness for your new gauges before installing the dash back in the car. If you decide you want to change the layout of the gauges or make room for air vents or an in-dash GPS unit later, you can change the insert.
Step-7: Install Switches
You can change the red toggle switch covers for black ones for a more subtle look. These are often called aircraft-style switch covers, and they are designed to shut off the toggle switch with just a quick movement of the hand. The switches themselves are mil-spec toggles from Painless Performance. They are internally sealed, and terminals with screws instead of push-on connectors. TJ also installed a Painless Performance Phantom Key push-button start system.
Step-8: Select Ignition Switch
The Phantom Key system works like a new Challenger or Cadillac push-button start. The remote fob must be within 20 feet of the car to arm the system. Once armed, you push the button to engage the starter. The starter cranks until you release the push button. To shut the engine off, you push the button again. The kit comes with a control module, two remote fobs, a push button, wiring, and a rack of relays to control accessories such as power door locks (see page 129 for more information on this system).
Step-9: Configure Dash for Your Needs
This is a typical ABC Performance dash with 5-inch Auto Meter speedometer and tachometer and four additional 2-inch gauges. There is room above the single-DIN radio for an air-conditioning vent. The area above the glove box requires a custom piece to fill the now taller area. ABC Performance can provide a trim piece such as the one shown covered in leather.
Step-10: Install Completed Dash in Car
The dash installs in the factory shell using the same fasteners as the original. ABC Performance can also provide LED indicator lights for the high-beam headlights (blue light between the speedometer and tachometer) and turn signals (green lights). This is a very clean way to install large performance gauges in your 1966–1967 Chevelle and have everything integrated into your dash, rather than gauges strapped to the column, or bolted on or under the dash.
Step-11: Fit Reproduction Door Panels
The rest of a performance Chevelle interior doesn’t necessarily require custom work. You can use reproduction door panels and a headliner from CARS, Inc. to complete a race-inspired theme. These upper door panel mounts were refinished in cobalt black by Advanced Plating for a cool, dark look with reflective properties of chrome. The new door panels have the cutouts in the back board for the window and door handles, but you need to trim the vinyl.
Step-12: Fabricate Dash Pad
You can cut a reproduction dash pad from CARS, Inc. to fit around the A-pillar bars. Custom leather upholstery can be added with detail stitching for a very nice look.
Step-13: Install Sound Deadener
You can cover the floor of the car with Eastwood Thermo-Coustic sound deadener. This reduces the road noise and vibration caused by a hot performance engine and exhaust system. The butyl membrane has a peel-and-stick backing for easy installation. The top side has an aluminum face to reduce heat. This type of product adds 30 to 50 pounds to the vehicle, but is well worth the weight penalty in any vehicle you drive on the street for the improvement in interior sound quality.
Step-14: Install Carpet
Another street concession is a good layer of carpet. This Daytona weave from CARS, Inc. has zero shag; a tight, woven appearance; and a very high quality weight of the material and a foam back, which adds further sound deadening. It does not come as a molded carpet set; you need to have it professionally installed.
A modern performance interior for your Chevelle can be functional with performance seating, safety harnesses, roll cage, instruments, and controls. Yet, it still can have the classic styling and theme of the vintage car that you love.
Written by Cole Quinnell and Posted with Permission of CarTechBooks