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Before tightening any of the...
Before tightening any of the muffler or tailpipe clamps, eyeball the system for straightness and make any necessary adjustments.
Because we've covered quite a few short-tube, mod-motor header installations, this time we're detailing the Evol system installation while also providing the test results of adding JBA Cat4ward headers, among other things. It's also worth noting that two '03 Cobras were sampled. The main attraction is a stock red convertible a customer brought in for upgraded exhaust; the second is J's personal blue coupe. We're happy to report all parts tested made worthwhile power improvements. Even with the stock H-pipe with stock catalytic converters in place, there is approximately 38 hp to be found with the Cat4ward short-tube headers and Evol system working with stock cats in the stock 211/44-inch H-pipe. That's not too shabby for straightforward bolt-ons.
Speaking of bolt-ons, if you can get the Cat4ward short-tube headers on your Cobra, you won't have any trouble with the Evol after-cat. We've never seen such an easy exhaust system upgrade. It's definitely a driveway job, if that's your thing.
J's Tester
Besides JBA's customer's '03 Cobra, J Bittle put us in his own '03 Cobra coupe for a quick tire smoke and around-the-block evaluation. Souped up with a 2.73-inch blower pulley for a couple more pounds of boost, a set of 131/44-inch primary midlength JBA headers, high-flow cats in a 3-inch H-pipe, and the same 3-inch Evol after-cat system as tested on the red car, J's car proved a rowdy good time.
Naturally, the all-3-inch exhaust system was bound to be heard, and it was. Actually, at idle the exhaust was surprisingly quiet, with a civilized burble rising from under the car like so many bubbles of exotic-car champagne. Get on the pedal, however, and the immediate world was bathed in a sonic discharge heavy enough to announce a serious power contender was at hand, but with the hard edges lightly rounded off. The Flowmaster Delta Flow mufflers receive high marks for their combination of plenty loud but not harsh. They were never "boomy."
Often the curved pipe under...
Often the curved pipe under the differential sags. Shim it using a piece of wood or other object until after the system is tightened. At JBA, Eric finds leftover hangers from other jobs give just the right fit.
While decelerating, the big and open exhaust provided a sporty snap, crackle, and pop as the engine leaned out.
Plenty loud when on the gas normally translates into too loud when using 1,700-2,200 rpm around town-or, with the Cobra's six-speed gearbox, on the freeway. And the cruising results were predictable-an audibly charged cabin perfect for priming the adrenal glands on Saturday night, but definitely overactive for a Tuesday-morning commute.
While inspecting the exhaust with the car on a hoist, we wondered if we'd opt for the big 131/44-inch primary headers. These tubes are so large, not much more than three sheets of paper could be slipped between the starter motor or frame-rails and the header tubing on the passenger side of engine. Given a newer car with fresh engine mounts and not impossibly frozen nuts and bolts, the practicalities of living with such tight clearances seem-well-possible. Indeed, the installation never thunked against floor or driveline, and proved leak-free. But you just know that eventually you'll have to end up working around those monster tubes. We can happily report that the midlength header does easily fulfill its main objective of providing good bellhousing/ clutch clearance, so those chores will not involve header hassles. In addition, JBA also builds these headers with 151/48-inch primaries, which should notably increase wiggle room around the collector.
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 JBA supplies a hefty, two-bolt...  JBA supplies a hefty, two-bolt band clamp for the tailpipe-to-exhaust-pipe connection. Simply tying it down is all that's necessary. |  At the intermediate-pipe-to-muffler...  At the intermediate-pipe-to-muffler joint, JBA supplies the usual U-bolt clamps. Because we would need to remove the intermediate pipes to try the 3-inch H-pipe, Eric simply tacked this connection with the smoke wrench. This prevented deforming the pipes with the U-bolts. The tack welds were easily cut off with a whiz wheel. |  Once on the car, the Evol...  Once on the car, the Evol looked as though it grew there. Clearance around the large pipes, the chassis, and the ground is ample. |