Swapping out the stock cast iron log exhaust manifolds for a set of ceramic-coated JBA shorties was the first performance change I made to the car. Although installing headers is a modification that most people don't consider until later, if at all, somebody on one of the Mustang forums had put together a JBA group purchase with prices far too good to pass up, so I jumped in. JBA's provide nearly the same performance gains as long-tube headers (a fact documented by Bob Cosby, among others), without the disadvantages of having to remove them for clutch/transmission work or Arizona emissions certification.
At the time of my purchase, JBA's were the only CARB-certified aftermarket headers available for my application. They may still be. Although I realize that fact isn't a consideration for many gear heads, it is for a few of us, and that number will grow as more states tighten emissions requirements.
Of course, the practical downside to installing headers on any late-model 'Stang is that the lack of working space makes the procedure very tedious, and this was, by far, the least enjoyable wrenching time I've spent on the car. I had heard that dropping the K-member makes the process somewhat easier, but I balked at that. Instead, I just unbolted the motor mounts and jacked the motor off the member about an inch or two to give myself enough room to work. Barely. If I ever swap out these headers, I certainly will drop the K-member. Take that for what it's worth. (See 2009 update below.)
The photos on the left in the composite below contrast the driver side JBA header with its counterpart factory exhaust manifold. The panel on the right of the composite shows the passenger side header from below during installation. In this panel, you can see my use of Stage 8 locking fasteners wherever possible - I did not want to face the ordeal of having to retighten standard header bolts later.
In addition to increasing performance by improving exhaust flow, tubular steel shorties offer a second benefit that many overlook. They generally weigh considerably less than the cast iron logs that most manufacturers bolt onto their engines. As I recall, in the case of the Cobra, each JBA header tipped the scales at half the weight of its cast iron counterpart. That's significant.
After several years of putting up with exhaust leaks and enduring the pain and suffering related to the nut-and-bolt fastener arrangement between the JBA collectors and the down-pipes, I finally swapped back to the stock exhaust logs in May of 2009. The leaks between the JBA primary flanges and the head had become so bad that I was probably losing more power than I was gaining with them, anyway. Regardless, the car had begun to sound like hell. My buddy Jim, a top mechanic who had all the equipment necessary to drop the K-member and the experience gained from swapping the K on his own Cobra, graciously offered to donate his time and efforts to the cause. Together, we were able to complete the swap in a single day.
Fortunately, I had never gotten around to selling the OEM manifolds, as I'd originally planned after installing the JBA's, so all I needed to buy for the project were fresh gaskets. Having learned my lesson the hard way regarding fiber exhaust gaskets, I picked up a set of Ford metal gaskets for the project. While we were at it, we also reinstalled all the original studs that I had replaced with Stage-8 fasteners while using the JBA's. (Yes, I still had all the studs eight years after removing them from the car. Sometimes, being a pack rat pays off.) In the photo below, you can see all the carbon around two of the driver side exhaust ports, indicating where the gaskets had been leaking. (Believe it or not, the leaks on this side weren't nearly as bad as those on the other side.)
And below, you can see the completely blown out passenger side gasket. Although both sides had been leaking, this is the gasket that had been causing most of the exhaust racket.
To avoid unduly raising engine bay temperatures with the reinstallation of the cast iron manifolds, I first wire-brushed them to remove the light surface rust, and then treated them with a bake-on silicon-based thermal barrier coating before swapping them back in. This helped to keep the temps in check.
I gave the JBA's to Jim to repay him for his time and effort, and he later sold them. Unfortunately, we had both completely neglected to check the integrity of the headers, themselves, after discovering all the leaks around the gaskets, and the new buyer soon sent Jim the images reproduced in the panels below. Oops! See the nasty crack where that primary is welded to the collector? Ouch!
Even though the crack is obviously quite repairable, Jim graciously refunded the buyer all his money and offered his apologies, and he told the buyer to keep the headers and do whatever he wanted with them. So, for the cost of a little welding work and maybe a fresh coat of Jet Hot, somebody scored himself a nice pair of shorty headers. But now I need to come up with some other way to reward Jim. Oh well, I'll think of something.
NOTE: Everything else being equal, reducing exhaust restrictions will lower the effective boost pressure of any forced induction application, while increasing those restrictions will have the opposite effect, so I expected my boost gauge to read a little higher at full boost after swapping back to the stock exhaust logs. After all, they couldn't possibly flow as well as the JBA's. However, that isn't what happened. My boost gauge actually reads a little lower since reinstalling the factory manifolds. Furthermore, the car will break the rear end loose even more easily now than before, so I certainly don't get the impression that I've lost any power.
Imagine that. Swapping the exhaust manifolds was the only change made that day, and the exhaust system is completely free of leaks. Did reinstalling the cast iron manifolds improve exhaust flow or not? Draw your own conclusions. I've drawn mine, and my opinion of the factory logs has improved considerably since then.
My second exhaust system upgrade, after the header installation, was the high-tech Ford Racing model FR500 catback system. The FR500 employs dual-mode mufflers and mandrel bent 2.5" stainless steel pipes, instead of the 2.25" piping used on the factory catback. It also incorporates an aft X-pipe to improve torque and help minimize exhaust drone. I neglected to shoot any photos of my catback installation, which only took about 30 minutes once I had the car on jackstands, but here is a Ford Racing stock photo.
TECH TIP: If you're going to be switching to an FR500, the easiest way to install this exhaust is to assemble and square up its three individual pieces on the floor, and then raise it into place as a single unit.
Most performance exhaust systems provide HP gains in the higher engine RPM ranges at the expense of low-end torque, but not this one. The FR500's mufflers incorporate pressure-sensitive valves that force them to operate in chambered mode during cruise for improved torque, but the valves open as exhaust flow increases to provide more top-end HP courtesy of straight-through operation. The valves also endow the exhaust with a genuine Jekyll/Hyde personality. The system is about as quiet as the OEM catback and very tame sounding up to about 3500 RPM, but the Cobra screams like an F1 racecar under hard acceleration. Cool. It appears that it is sometimes possible to have your cake and eat it, too. Follow the link in the footer of this page to read a test report of the FR500 catback by Muscle Mustangs & Fast Fords. Pay particular attention to the power increases indicated by the dyno. They're impressive.
2009 UPDATE: Ford Racing has discontinued the FR500 catback, probably due to sluggish sales. This means that, unless you happen to be lucky enough to locate a used example in good shape, your window of opportunity to score one of these truly outstanding systems has closed. I'm just happy that I had the presence of mind to grab one while they were available, despite all the naysayers carping about the price of admission.
Editorial Comment: FR500 sales may have been poor because of the system's premium price, but it's more likely the FR500 just didn't sound "mean" enough to suit most pin-headed knuckle draggers. The FR500 lacked an intimidation factor, because the baritone muscle car rumble was absent, and the Great Unwashed tend to equate a menacing exhaust note with power. Hey, the louder it is, the faster it is, right? Wrong. Making a racket is NOT the same as making power. I challenge you to find another catback system that delivers equal or better power gains to those provided by the FR500 - 13.6 RWHP and 15.1 lb-ft of RWTQ. Nevertheless, thanks to a lot of stinkin' thinkin', the best aftermarket catback for New Edge and Terminator Cobras is no longer available, and that's everyone's loss.