THE AUTO BUILDER

Featured

Have you ever been driving down the freeway or working on your car when that brilliant idea hit you? The more you thought about it, the more brilliant the idea became. When you called your friends for reinforcement, to see if the idea was actually as brilliant as you thought, there was always the chance they might pop your bubble. There are times you find the idea might only be brilliant to you, but other times it could be a life-altering idea, and the start of something that will endure over time. Dick “Scritch” Scritchfield had one of those brilliant ideas back in 1957, when he was working for the National Hot Rod Association’s Safety Safari. It turned out to be a great idea that received plenty of support from his peers. He wanted to start a car club for roadster owners that would reinforce the hot rod hobby.

TO THE POWER OF FUN

When you’re talking power, few know more about it than Joe Granatelli. Not only does he come from the legendary Granatelli racing family, Granatelli is a licensed Pro Street drag racer and spent time as an instructor at the Roy Hill Drag Racing School. In 1989, he founded Granatelli Motor Sports, and since that time he has been busy designing and manufacturing items that add power to your truck or car. Those items include the Big G systems as well as exhaust and other high performance systems for not only gas and diesel pickups, but also for some fast Mustangs as well.
Two of those performance items are the Fuego Tuner and Hi-Performance Coil-On-Plug Connectors. The Fuego is a hand-held computer tuner that not only adds horsepower, it allows the person to control many of the actions associated with increasing the performance of the truck. Do you want the trans to shift not only firmer but also at a different rpm than the stock unit? The Fuego is capable of doing it. Do you have bigger tires? No problem. Want to retard or advance the spark? The Fuego can do that too.

River Rod Royalty

Inside the 2026 Grand National Roadster Show, the thunder didn’t stop at the hot rods. Tucked among the country’s finest customs and street machines was a killer lineup of vintage ski hydros, circle boats, and heirloom river runners that brought serious waterborne attitude to the show floor. Blown big-blocks, hand-laid gelcoat, and family-built history were on full display, proving that the hot rod mindset runs just as deep on the river as it does on the street.

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.