Tom Wilson
December 20, 2006
It's another hot-rod interior until you notice the automatic transmission shifter. Even that has remained stock, as the prepped 4R70W doesn't need any help shifting.

A couple of unusual requirements arise at this state of tune. For starters, a taller Cobra R hood is required to clear the sewer-sized Cool Air plumbing, and the big Cobra fuel system needs a modified pump driver. The Two-Valve GTs come with a single pump driver-a compact circuit board that controls fuel pump output that's in the trunk-that soon can't handle the Cobra dual pumps' amperage needs. Kenne Bell's answer was to fit a second driver. This is an absolute must if SVT Focus fuel pumps are substituted for the stock Cobra pumps, which is a common upgrade, as stock Cobra pumps support up to 650 rwhp and the SVT Focus pumps 750 rwhp. All of this fuel pumpery is in addition to a Kenne Bell Boost-A-Pump which steps up the pump voltage as required. The good news is the entire 700hp returnless fuel system, drivers and all, is now available exclusively through Earl's Automotive [(818) 838-7154]. They can give you the details on the pump fusing requirements and other details.

Electronic tuning was done in-house at Kenne Bell's by Ken Christley. While hundreds of dyno runs were made with about as many different calibrations, it all boiled down to one of Kenne Bell's switch chips. Anyone hoping to duplicate this car would be forced to custom-tune it, although KB could get you close right off the bat because they have so much development tuning done already.

Jim Bell admits he's found plenty of horsepower on the inlet side of superchargers, and he has the low-restriction intakes to prove it. The cool-air intake leading to the 90mm Cobra mass air meter is his breathing aid for big-power applications. It mounts a large conical air filter in the inner fender, then connects it to the air meter with giant 5-inch-diameter flex hosing.

The front-engine dress is a more mechanical concern. The stock Mustang GT uses a six-rib, 6.5-inch-diameter pulley, and there are several options to deal with the blower-ratio and belt-wrap issues. What's needed is a large-diameter crankshaft pulley. KB makes these by machining and then sleeving a 4.6-liter Triton truck crank damper/pulley to arrive at an 8.5-inch-diameter crank pulley. This large pulley fowls the water-pump pulley, so Kenne Bell tried going down an inch to a 4-inch-diameter water-pump pulley, which proved a disaster. The water-pump speed was much too fast, and the resulting out-of-control water pump resistance cost 26 rwhp before the water hoses blew off. KB then went to an electric Meziere water pump, which cured the issue. The end result for ultimate power is a six-rib system with the electric pump and an 8.5-inch-diameter crank pulley. KB says the six-rib pulleys give adequate belt wrap given the large pulley diameters. Alternately, a 7.5-inch-diameter crank pulley with a 5-inch water-pump pulley on the conventional water pump is fine for 500 to 600 rear-wheel horsepower, with only a 1hp loss attributable to the overspeeded water pump.

Chassis-wise, Kenne Bell tried a fair number of bolt-on solutions before reverting to a nearly stock chassis fitted with Mickey Thompson drag slicks on the strip and Nitto Extremes for street duty. Lakewood drag struts up front provide the necessary weight transfer, while a D&D K-member reduces weight and provides header/working clearance.

So, how did it all work out? We're showing the stock and highest-power dyno results. Even given the big boost, prepped engine, non-emissions configuration, and custom electronics tuning, the 431-rwhp gain is still mighty impressive. The final tally was 642 rwhp at 20 pounds of boost on 100-octane fuel. This was with the low, 8.1:1 compression engine and through the automatic transmission. Jim Bell says the same configuration with a manual trans is worth an additional 40 rwhp, or 682 rwhp. That gives this Two-Valve the edge over the earlier Four-Valve test by approximately 20 hp when both are tuned way out to the edge.

Yes, the Colorado Custom wheels in front are larger at 18x10 inches. They mount Nitto 255/35AR18 Extremes and do their best to obscure a set of Baer brakes underneath.

More real-world is an intermediate set of numbers at 579 rwhp from 15 pounds of boost and 91-octane gas. Again, that's with the prepped engine, 8:1 compression, and automatic trans. KB reports the car behaves nicely on the street in this configuration. We didn't drive it, but there's no reason why it shouldn't, although the low compression means it won't be super snappy or return stellar fuel economy when off boost. But it shouldn't be a dog, either, and what the heck-you can always step on the throttle.At the Fontana dragstrip, Kenne Bell reported a 10.32-second/134-mph pass with 20 pounds of boost and 118-octane C-16 race fuel. Running at the limit of 91-octane pump gas-15 pounds of boost-netted a 10.71/127 timeslip. Not bad for a full-weight Mustang GT.

And what about those hoped-for 9-second passes? Traction was an issue, and when KB tried for 9s with 24 pounds of boost, ignition breakdown was a problem. After trying some exotic arc-welder aftermarket ignitions, Jim Bell says the best spark was the stocker amped by his Boost-A-Spark.

So, the 9-second pass is still to be had, and considering this yellow Cobra-killer has left Kenne Bell, along with Brent Morris, the single-digit track heroics are awaiting work on the short times and likely some weight reduction. But isn't it amazing to think it's even possible?