More Power and Torque for Corvette C5s

The new Bassani 421-series header and Aft-Cat system net 30 more HP and35 lb-ft more torque than a stock C5 system

Cam Benty Sep 16, 2004 0 Comment(s)

When the '97 Corvettes burst upon the scene, few could find fault withthe newest offering from Chevrolet. In fact, the improved handling,styling, and performance were so overwhelming that it took a careful eyeto find where additional aftermarket components would make a difference.That is, except for one area: the exhaust system, which suffered from apoor exhaust note and restrictive, power-robbing plumbing.

Bassani, a performance exhaust product leader in both the automotive andmotorcycle arenas, has developed a system for '97 to '04 Corvettesequipped with LS1 and LS6 engines. Designed at its facility in Anaheim,California, recent independent testing by Roger Vinci of VinciHi-Performance, using a stock LS1-engined '02 Corvette featuring allstock components (automatic transmission and factory 3.15:1 reargearing) netted an amazing 30hp increase and 35 lb-ft of torque over thestock baseline numbers. In dragstrip testing, the Bassani-equippedCorvette improved overall quarter-mile e.t.'s from 13.83 and 101.45 mphto 13.33 and 104.50 mph, proving the power gains from the system areindeed very real. Best of all, at the time of this writing, Bassani haddecided to file for a California Air Resources Board Executive Ordermaking the system 50-state legal for '97-'99 LS1 and LS6 engines.

Subsequent testing by Superior Automotive with a manualtransmission-equipped car measured 342 hp on the dyno using the "421"headers, Aft-Cat, stock converters, and K&N air-filter kit.

The Bassani Xhaust system features either 13/4-inch or big-tube17/8-inch primary header tubing, making the latter perfect for big-inchengines like the 427ci, which is becoming popular with C5 Corvetteenthusiasts. The headers themselves are made from mild steel with aceramic coating. The multi-piece header system makes home installationnot only possible, but quite easy for the novice. Using the factorycatalytic converters, the system mounts the stock oxygen sensors in thefactory locations, making the system compatible with engine computeroperation. The exhaust system, from the catalytic converters back to thetailpipes, is made from stainless steel for long life and a great finallook. The Bassani Xhaust system includes all of the proper hangerattachment components and is a well-engineered system for the C5Corvette. The twin-outlet tailpipe system is unique, a signature Bassaniexhaust design.

The Bassani Xhaust system delivers tremendous real-world, streetablehorsepower. An excellent addition for the C5 enthusiast looking forenhanced performance and improved performance sound, the Bassani Xhaustsystem is competitively priced for the market.

Baseline vs. Bassani

Bassani Xhaust turned to an independent source, Vinci Hi-Performance inOrlando, Florida, for testing their system. Joe and Roger Vinciinstalled the system and conducted baseline and modified testing of theBassani 13/4-inch tri-Y headers, Bassani Metalicat System fitted withthe Bassani Z06 center-mount muffler on an '03 automatic-transmissionCorvette. No other modifications or tuning were conducted on thevehicle, which was in desperate need of an air-cleaner change as debriswas found in the silencer after the testing was conducted. After asimple air-cleaner replacement, 6 hp was found on average, which is notreflected on the dyno chart below.

All results are corrected to 29.92 in/Hg, with the vehicle tested inSecond gear.

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1 Clean and functional with improved engine power and greatexhaust note--what more can you ask of an exhaust system?

2 This is where you start on your LS1 or LS6 engine. With the oldexhaust system out and the engine disassembled enough to make room forthe header pipes, you're ready to begin.

3 The catalytic converters from the original factory system areused with the Bassani X-pipe system. The flange of the catalyticconverter must be prepped in this manner to adapt to the Bassani system.This modification can be performed at your local muffler shop.

4 The headers are a multi-piece unit, making them easy toinstall. Both 13/4-inch and 17/8-inch primary tube headers areavailable.

5 (above & below) The header-to-engine block mating surface must be clean andsmooth to avoid engine-damaging exhaust leaks. These Bassani-designedinserts and header-flange system ensure a tight, leak-free seal.

Click the picture above to view the specs chart on a basline C5 vs. the Bassani-equipped C5.

Graphical interpretation of the baseline C5 vs. Bassani-equipped C5.

First Impressions

When it comes to Corvette and late-model Chevrolet performance, RogerVinci of Vinci Hi-Performance always has an opinion with credible merit.After conducting the baseline and Bassani Xhaust testing, Roger said, "Iwas very impressed with the entire system Bassani sent us. We havetested exhaust systems for most major C5 system manufacturers and, whileI always find things I like and things I do not, most manufacturersappreciate the critique and attempt to correct issues that we find."

In the case of the Bassani system, Vinci not only conducted chassis-dynobaseline to Bassani tests, but also drag testing. At Orlando Speedworldon July 30, 2003, the stock automatic-trans Corvette made a 13.83/101.45pass. With the exhaust system installed, on September 10, 2003, roundtwo testing was on. The results: 13.33/104.5. That's an impressive 0.5second quicker in the quarter-mile and nearly 3 mph faster through thetraps!

And while the performance was pleasing, Roger Vinci had even more praisefor the Bassani system. "A few items that stood out on the Bassanisystem were first the header-to-cylinder head gaskets they furnished.They are a work of art. They consist of a pair of machined plates fittedwith soft packings at each port. This system presents a positive sealthat will probably never need replacing.

"Second, the tri-Y header is a 4-2-1-style header. The headerincorporates a technique whereby two cylinders per side are connectedtogether into two separate collectors, then the two collectors areconnected into a third collector--thus '4 into 2 into 1.' This technique,coupled with the unique optimum-length tubing, provides the huge torqueincreases the header demonstrated on the chassis dyno. Obviously, thismuch plumbing requires more pieces for the installer to deal with.Bassani separates these pieces for easier installation, then provides aneat system to fasten them together. A pair of short tubes are weldedalongside a slot on each of the primary pipes of the slip-fitted tri-Ycollectors. Allen-head bolts are provided to complete a leak-freepackage.

"The rest of the system utilizes fitted flanges and ball-end fittingsfor a perfect, adjustable, rattle-free fit. The third item I foundimpressive is the Ferrari-like exhaust note that's so different from anyof the other systems we've tested. Upon testing the car on the road, Iwas equally impressed with the very noticeable increase in brute powerat low-end and midrange rpm. The power is right where you want it. Youknow, we spend very little time at 6,000 rpm and a whole lot of timebetween 1,500 and 5,000, and that's where this system really performs."Roger concluded by saying, "I highly recommend this system to any andall street and strip or autocross enthusiasts."

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6 The first piece of header tubing is installed from below on thedriver side.

7 The second piece of the header system is installed from above,and make sure not to damage the spark plugs.

8 With a slight amount of manipulation, the headers line up andfall into place with little effort. They are left untightened while thebottom collector flange system is installed.

9 With the collectors in place, the headers will look like this.The collector system bolts in place with pinch clamps to avoid exhaustleaks.

10 With the catalytic converters bolted to the collectors, theoxygen sensors are screwed back in their original locations. These twooxygen sensors are at the back of the catalytic converters. The LS1 andLS6 engines utilize four oxygen sensors. The Bassani X-pipe systemincorporates all of them.

11 The pre-catalytic converter oxygen sensor is mounted in thehole located in the header flange of the Bassani system.

12 The after-cat portion of the Bassani X-pipe system is made ofstainless steel. The secret of the system lies in the X-pipe located inthe muffler-shaped portion of the exhaust. Good stuff happens in there!

13 (above & right) The X-pipe is slipped in place and held with clamps andhangers similar to the OEM system. Overall ground clearance with thesystem is 1 inch higher than the OEM system.

Sources

Superior Automotive
Anaheim, CA 92801
714-503-1880
www.superiorautomotive.com
Vinci Hi-Performance
Orlando, FL 32808
(407) 292-4500
Bassani Performance
Anaheim, CA
www.bassani.com
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