By Richard Holdener/Photos By Author
What looked like a Shelby 289 Ford, was actually a Comp-cammed, stroker ready for some serious action.
If you are a Mustang, or even Ford fan, chances are strong that you have heard the name Shelby. An accomplished racer, Mr. Shelby was best known for providing the world with one of the most widely recognized automotive icons, know affectionately as the Cobra. Though the over-powered, little snake usually got top billing, Carroll Shelby also accomplished what was thought to be an insurmountable task, but besting no less than the mighty Ferrari at their own game.
With help from designer Pete Brock, the (Cobra) Daytona Coupe won the FIA championship, using Ford’s little 289 Mustang motor no less. Shelby was also instrumental in the tremendous success of Ford’s own GT40 project, winning the 24 hours of LeMans endurance race no less than four times. Recognizing that racing success improves the breed (even if just at a marketing level), Ford was quick to attach the Shelby name to their new pony car, the Mustang. Though Shelby built specialty Mustangs from 1965-1970, the association helped sell endless versions of the standard Mustangs as well.
In terms of performance, the Shelby Mustangs (and small-block Cobras) were only slightly more powerful than their production-line counterparts. The factory HiPo 289 was rated by Ford at 271 hp, while the Shelby version offered 306 hp, thanks to a revised induction system and Tri-Y headers. Fast forward a half century or so, and the Shelby Mustangs command some serious coin, to say nothing of a true Cobra.
The pricing has pushed the cost of ownership well beyond the reach of most Ford enthusiasts, and to be honest, we are not sure a Ford fanatic would be happy with the performance, even if they had an original. Despite all the snake-oil offered by Shelby, even the 306-hp 289 was never a serious performer. It lacked the displacement of even other small motors like the DZ or Boss 302, to say nothing of the 327, 350 and 351 small blocks of the period. This doesn’t even taken into account the big blocks, but we will keep our focus on the smaller motors that fit right into an early Mustang (or other mid-late 60s Ford)
With a real Shelby being inexpensive and underpowered, many enthusiasts are building clones. That is when you take a standard Mustang and make it look and sound like an original. There are several great things about a clone, including not having to worry about putting miles on it, not having to be 100% original, and, best of all, the ability to make it perform even better than the original.
To that end, we decided to build up a realistic small-block Ford that looked like the original 289, but offered considerably more power. Naturally we wanted to start with a hike in displacement over the original 289, but the taller deck of the 351W limited fitment, so we stuck with the standard deck-height of the 289/302. To add inches, we combined a .030-over, late-model, 302 block with a 3.4-inch stroker crank to produce a finished displacement of 347 inches. Right off the bat, the little Ford was up 58 inches over the Shelby 289, so we were off to a good start, but only if we managed to properly feed the extra inches.
Knowing that we wanted the Shelby clone motor to make decent power AND drive acceptably, the most important part of the little stroker was actually the camshaft. Understanding the cam determined the personality of the motor, we chose a grind from Comp Cams designed specifically for a stroker application. The XFI236HR-14 cam from Comp Cams was actually designed with fuel injection in mind (for a 5.0L Mustang), but this cam (.579 lift, 236/248-degree duration split and 114 degree lsa) worked equally well on our carbureted 347.
The cam was wild enough to offer both a noticeable idle (to impress the cruisers at your local Cars and Coffee) and serious performance. Though powerful, the cam was mild enough in the 347 stroker to allow for use as a real driver. The XFI cam was teamed with a set of Comp link-bar lifters, a double-roller timing chain and a dual-spring package to ensure uninterrupted trips to 7,000 rpm. Comp Cams also supplied the necessary 1.6-ratio, aluminum roller rockers, as no self-respecting stroker should ever be sporting stock, stamped-steel rockers. The rockers and spring upgrade were teamed with a set of hardened pushrods, as the last thing you want is pushrod deflection or (even worse) failure on your high-rpm stroker.
With our valve-train choice in place, we now needed supporting components to allow the XFI cam to really shine. To that end, we installed a set of aluminum KC LH 17 195 heads from Brodix. The peak flow numbers near 300 cfm (intake) and 214 cfm (exhaust) for the aluminum heads compared nicely to either stock 289 or 302 heads that offered roughly half that. Looking back, it was impressive that Ford and Shelby managed to coax the power they did with such lackluster head flow. The aluminum heads flowed well, even past the near .600 lift offered by the XFI cam. The increased port volume offered by the Brodix heads also favored the rpm potential and additional displacement of the Comp-cammed 347.
To keep the combination streetable and promote plenty of torque production, we equipped the Shelby clone with a dual-plane intake and 750 carb. Of course, this would all be hidden under a set of finned-aluminum (Power by Ford) valve covers, a finned-aluminum, Cobra oil pan and (not shown in photos) a Cobra-logo air cleaner set up. The 347 should make plenty of power, but the small block also had to look the part, right?
Having run reproductions of both the HiPo and Shelby versions of the 289 in the past, we knew how they performed. Both the 271-hp, HiPo 289 and 306-hp, Shelby versions were accurately rated, assuming the testing was run like we do, with optimized timing and air/fuel and long-tube headers. We doubt they had electronic water pumps back when they were testing these motors in the 60’s, but the numbers were still pretty accurate.
Naturally we were looking to exceed these numbers by a substantial amount with our stroker, and that is exactly what happened. Run in anger after a couple of break-in cycles, the XFI-cammed 347 produced peak numbers of 479 hp at 6,600 rpm and 424 lb-ft at 4,800 rpm. Thanks to the extra displacement and right combination of components, what looked like any other carbureted small block (decked out in Shelby guise) improved the power output of the HiPo 289 by nearly 200 hp. Imagine what your light-weight, early Mustang would feel like with an extra 200 hp, to say nothing of an extra 100 lb-ft of torque. Those original 289s were hardly torque monsters! Armed with this stroker, your Shelby clone (or any early Ford) should now cook as good as it looks.