SpinTech’s Chris Anderson is busy installing one of their oval-tube exhaust systems under a ’61 Chevy at their shop in Riverside, CA.
Little did Ron DiDonato know when he started Superior Metal Fabricators back in 1979 that, more than 30 years later, his business would involve making performance-minded exhaust systems for all sorts of cars and trucks. At the time, Superior was based in Anaheim, California, and was a go-to for folks who needed specialized equipment fabricated, such as stainless steel items used in the hospital supply business.
But having a side interest in racing sprint cars opened up other opportunities in manufacturing and, when the racing world changed its rules concerning decibel ratings of the race cars, DiDonato worked at building compliant muffler systems for the racers, and soon began working with and shipping directly to a lot of the race teams involved in the sport.
To keep up with the demand, DiDonato started SpinTech Performance Mufflers in 1995 and moved into a new shop located in Riverside, California. SpinTech was beginning to make a name for itself and, after DiDonato saw what was being done with mufflers in the race world, he began thinking about building performance mufflers for the street.
Through the ’90s, the SpinTech side of the business was outpacing his other business, and the company gained a reputation as a problem solver: If you had an odd application, you went to SpinTech because they’d develop a complete exhaust system for you, from the end of the header to the tip of the tailpipe.
By 1997, when SpinTech developed the use of oval tubing in their exhaust systems, things really started to get interesting. By using oval-shaped tubing, they were able to effectively run the same amount of volume through a 1-3/4x3-inch pipe as they could a 2-1/2-inch round pipe. They can easily accommodate the need for 3-1/2x6-inch applications (equivalent to a 5-inch round), and have custom built even larger setups for customers when needed.
The space saved by using the oval tubing allowed SpinTech to tuck an exhaust pipe up closer to the floor of the car, usually eliminating any chance of it hanging down below the frame or rocker panel. And for lovers of lowered cars, this simple change was a godsend.
A portion of SpinTech’s business has come about because no one offered solutions for newer cars, either (Pontiac GTOs from 2004-06 and Dodge Dakota trucks are just two popular examples SpinTech can supply exhaust systems for). DiDonato admits he does like the challenges associated with unique applications because it allows him to find creative ways to solve routing problems.
Such is the case with the X-frame cars found under ’58-64 Chevys. On earlier cars of the ’30s and ’40s, it was a simple fix by running the exhaust inside of a framerail and parallel to the driveshaft but, with this type of X-frame, it is exceedingly difficult to run any performance-sized exhaust, unless you do it with SpinTech’s oval tube (they offer it in 2-1/2- to 6-inch sizes).
SpinTech also offers complete exhaust/muffler kits as well as individual parts and pieces to complete any job, but to figure out what was specifically needed for a ’61 Impala (no “kits” exist), we followed SpinTech as they designed and built a system using their 1-3/4x3-inch oval tubing (similar in volume to 2-1/2-inch round) and a pair of their mufflers. The end result provided a nice rumble at idle and just enough “noise” to indicate there was something under the hood without it being overwhelming to the ears. Like DiDonato says, if it sounds too good to be true, it’s SpinTech!
With the fabrication of the exhaust completed, all that was left was to add some heat insulation to the floorboards above the mufflers and wrap the exhaust with some composite fiberglass material from Design Engineering Inc. (DEI). Wrapping the exhaust is easy (DEI’s website gives you the formula to figure out how much you’ll need) and it comes in 15-, 50-, and 100-foot rolls in both 1- and 2-inch widths.
DEI claims a 50 percent drop in underhood temperatures when using their wrap and it certainly helps when you have to run an exhaust system up close to the floor (as in just about every hot rod). They also sell stainless steel locking ties to finish off the ends of the wrap job. As for DEI’s Floor & Shield II material, it has a 10-mil aluminum face bonded to 1/8-inch composite glass-fiber core and is backed with a pressure-sensitive backing. It’s similar in concept to what rodders use for sound deadening inside their cars (and it can be used for that, too) but this material can withstand up to 1,750 degrees of direct continuous heat. The material is 3/16-inch thick and comes in three sizes: 21x24-, 21x48-, and 42x48-inch sheets and, after making some templates, an installer can easily cover whatever they need.
And, after investing in a custom exhaust system for your ride, a little bit of insurance to help keep it (and you) running cool would seem to make sense. The following photos show how the exhaust was custom-made by SpinTech and then wrapped with DEI products.
Routing of the exhaust begins where the DEI heat-wrapped headers end: with a ball-and-collar, gasketless connection. This short section of exhaust before the first weld utilize SpinTech's 2-1/2-inch oval tubing, which measures out at 1-3/4x3 inches.
The X-frame used by Chevrolet between 1958 and 1964 is especially hard to work around when designing and routing an exhaust system. Both sides of the exhaust are immediately run to the outside of the X-frame.
An advantage of the oval tubing is SpinTech was able to fit the exhaust above the low point of the frame by about a 1/4 inch. SpinTech also uses modern-style rubber hangers to suspend the tubing, allowing for metal expansion.
Looking inside a SpinTech muffler you’ll find SpinTraps, which provide the correct amount of backpressure as well as a pleasant exhaust note. After the two halves are welded together, the smaller six-trap unit on the right is what is typically used on Camaros and Mustangs, while you’ll find the larger eight-trap muffler on the left in larger vehicles, such as Impalas and trucks.
For this application (with the X-frame under a ’61 Impala), SpinTech miter cut a corner in their muffler to aid in routing and fitment.
With SpinTech exhaust systems, there is a male and female section to the tubing where the flanges meet up, making for a much better seal over other manufacturers who use only a gasket between the flanges.
As the exhaust nears completion, you can see how it follows the only open space in the Impala’s X-frame design.
SpinTech’s round-to-oval tubing allows them to convert a 2-1/2-inch exhaust into a 1-3/4x3-inch system with the added benefit of saving space.
Chris Anderson TIG-welds the over-axle part of the exhaust, where it twists from a horizontal plane to a vertical one and then back to horizontal.
In place, you can see what kind of clearance there is (not much!) between axle housing, coil spring, and frame, plus you have to consider the inside edge of the wheel, too.
Here’s the transition between the oval and back into a round piece for the tailpipe section.
For the tailpipe, SpinTech roughs out the routing by first tack-welding the sections together.
From there, measurements are made of each angle, and are transferred to a large machine (capable of bending 4-inch stainless!) that accurately bends a single piece of pipe into the desired shape.
The tailpipe now follows the shape of the roughed-in template part.
The single tailpipe section on the driver side looks factory in its presentation, and is finished with a down turn tip (used when you want the exhaust to disappear from view).
This photo shows both sides of the exhaust exiting on either side of the Impala’s gas tank.
The first step in wrapping an exhaust is to soak the wrap in a bucket of water. It makes it a bit more pliable, but it will also shrink a bit when it dries, thereby making a tight fit on the tubing.
At one end of the exhaust tubing, the wrap is folded under on itself for a clean start.
As you wrap the exhaust, you should be covering about half the width of what you just installed as you work your way down the pipe.
When you get to an end, fold the wrap under itself and secure it with a pair of DEI stainless steel locking ties.
Some folks like to secure their wrap with stainless steel safety wire, too. The installer used both methods on this exhaust.
The underside of the floorboards will be getting some of the heat shield material and, after making some paper templates, it gets trimmed and cut.
Here’s the area that was covered above each muffler. It goes on easily with its self-adhesive backing, but it’s wise to use a hard mini roller to tightly secure it to the floor.
Here’s the entire exhaust covered with heat wrap, and now the car is ready for the road.