MOD MOTOR 4-PLAY
December 12, 2022
THE AUTO BUILDER
Featured
Horseless Carriages Roar Through Monkey-Town
Over its history, the HCCA has been pivotal in orchestrating events, rallies, and exhibitions spotlighting antique automobiles, offering a platform for enthusiasts to exhibit their cherished vehicles, exchange expertise, and cultivate enduring connections. This year, the 2024 HCCA National Convention and Tour made its way through Chattanooga, Tennessee, and surrounding areas.
E-BODY MOPAR AIRBAR
If you lived during the muscle car era or have any experience with the E-body Mopars—’Cudas and Challengers—then you understand that these were factory rocket ships that were pure excitement to drive. Perhaps you recall those Plum Crazy 340 six-pack ’Cudas and 440 six-pack Challengers—they were hot back then, and they’re even hotter to own now.
A FAMILY AFFAIR
In the summer of 1977, a young couple expecting a son decided to purchase a new family vehicle, one that would provide ample room, safety and the ability to handle their love of camping and the outdoors. After deciding on a Chevrolet, the couple headed out and purchased a new ’78 two-wheel-drive Blazer from a dealer in Knoxville, Tennessee. Optioned out nicely for the time, the Blazer was equipped with A/C, a 400-inch small block, an automatic transmission, power disc brakes and a factory tach-equipped instrument cluster.
After driving the Blazer for several years, the couple decided to present it to their son, Travis Griffin, as a 16th birthday present. He drove the Blazer to and from high school, and then was given the opportunity to have the Blazer painted for graduation.
Spotlighter
AFTER-CAT INSTALL
A System to Upgrade an Aging Exhaust
Author
Marshall Spiegel
Story & Photography
The white ’99 Silverado was beginning to show the wear and tear of fighting the highway wars the last few years. The once proud and pampered show truck—a standard cab shortbed with matching cab-high camper shell—hadn’t spent much time in daily service until recent years, but now it bore its share of dings, dents and scratches. It was obvious that the 50,000 miles on the odometer hadn’t done the 5.3-liter V-8 much good. Part of the reason for the dissipated performance was the exhaust system, a very tired, less-than-top-quality aftermarket after-cat that had started banging, squeaking and leaking.
Installing a new after-cat from MagnaFlow was at the top of this owner’s agenda. He acquired a MagnaFlow (part No. 15617) polished stainless steel aftercat performance system for his Chevy, and because he’s in the automotive business and has a lift at his own facility, all he had to do was enlist the help of a colleague experienced in exhaust system installs to lend a hand with the hookup.
Both after-cat systems—the old aftermarket system previously installed in the Silverado and the new MagnaFlow system—are mandrel bent, which means that the tubing is the same diameter and configuration throughout. For cost and speed of manufacturing reasons, original factory systems are, for the most part, press bent. This means that the tubing is slightly distorted (pinched) in places along the bend. These cheaper, press-bent factory systems do not do as effective a job of evacuating exhaust gases, which is why aftermarket systems such as the MagnaFlow are known to produce a little more power, depending upon the system and application. In addition, the MagnaFlow system, advertised as a “straight-through” performance exhaust, is devoid of restrictive baffles in the muffler.
The reported performance level of a stock ’99 5.3-liter Silverado is about 228 hp. With an aftermarket system like the one removed here, the Silverado would likely produce 230-236 hp, while the MagnaFlow system is claimed to produce 240-248 hp. You might also expect some advantage with the MagnaFlow system in fuel mileage—perhaps up to a mile per gallon, if driven accordingly. While we did not test these results, any decrease in backpressure is a move in the right direction.
Installing the MagnaFlow system in this Silverado proved to be a quick, straightforward install. The accompanying photos show those highlights.
Here’s the Magnaflow after-cat performance exhaust with polished stainless steel straight-through muffler for the ’99 to ’01 GM 4.8/5.3-liter.
The ’99 Silverado had been struggling with this tired, less-than-ideal aftermarket system that was obviously showing its age.
By the time the installation of the MagnaFlow system was scheduled, the over-the-axle exit pipe section of the old system was in very bad shape.
For the first step in removing the old aftermarket system, a Sawzall was put to work cutting the old piping just behind the muffler.
The cutaway section of pipe at the rear of the muffler was pulled out of the way.
The Sawzall then did its thing, cutting the piping just in front of the muffler.
The old muffler was removed.
Our installer then unbolted the four nuts from the two U-bolts securing the exhaust system flange to the OEM flange of the catalytic converter extension.
The section of piping released when the flanges were unbolted was removed.
A close look at the old aftermarket system just removed (right) makes it easy to see why this Silverado was ready for the new MagnaFlow performance after-cat.
Our installer wrestled the new piping into place to position the MagnaFlow system for installation.
The flange of the new MagnaFlow piping was bolted up to the OEM flange of the catalytic converter extension reusing the original hardware.
The “much-too-pretty” MagnaFlow polished stainless steel muffler was positioned for installation.
Next our installer positioned the over-the-axle section of piping that goes from the muffler out the rear of the vehicle.
The original factory hangers were hooked up to hold the new system securely in place.
The piping was fitted into the rear opening of the new MagnaFlow muffler and the coupling was positioned to be tightened.
The piping was then fitted into the front opening of the muffler and that coupling was loosely tightened.
When our installer was satisfied that each section of the new system was properly placed, he began the final tightening, first at the bolts joining the flanges.
He then hand tightened the nuts holding the coupling at the rear of the muffler.
With his air ratchet, our installer further tightened the coupling nuts.
Just to make doubly sure the coupling nuts were secure, our installer gave them one last turn with his box wrench.
It is said that a level exit tip makes for the most efficient evacuation of exhaust gases.
The end of the polished stainless steel exhaust tip and the MagnaFlow sound are the only discernible clues that this old Chevy still has it goin’ on.
ARTICLE SOURCES
MagnaFlow Performance Exhaust
22961 Arroyo Vista
Rancho Santa Margarita, CA 92688
949/858-5900
