Donald Farr
Former Editor, Mustang Monthly
January 1, 1998

1965 289 High-Performance Automatic

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Actual Rear Wheel: 141 hp/254 lb-ft

Estimated at Flywheel: 176 hp/318 lb-ft

Factory Rating: 271 hp/312 lb-ft

Jeff Burgy from White Lake, Michigan, has owned his white Mustang K-GT convertible for three years. By Jeff's best estimate, the Mustang was completely restored, including an engine rebuild to factory specifications by a previous owner about 15 years ago. Jeff figures his 289 High-Performance engine has about30,000 miles on it since the rebuild.

Ford rated the solid-lifter 289 High-Performance at 271 hp at the flywheel, but on the Dynojet, Jeff's K-GT generated only 141 hp at the rear wheels. Of course, the automatic soaks up a lot of power, at least 25 percent by Dynojet's calculations, which gives us a 176hp reading at the flywheel. Interestingly enough, Ford's rating came at 6,000 rpm, but Jeff's convertible hit its peak at only 4,500 rpm, then started losing horsepower as the revs climbed. Jeff's convertible produced more net torque, based on the 25 percent calculation, than the factory rating.

To put it into modern perspective, the 141 rear-wheel horsepower from Jeff’s automatic K-GT is less than 20 hp off from automatic-equipped 1996-1998 Mustang GTs’ 4.6L V-8s. With some good tuning to gain horsepower in the higher rpm range, Jeff’s K-GT would no doubt outperform today’s new Mustang GTs.

1965 Shelby GT350 Four-Speed

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Actual Rear Wheel: 202 hp/237 lb-ft

Estimated at Flywheel: 236 hp/277 lb-ft

Factory Rating: 306 hp/329 lb-ft

Rebuilt and even rebodied from a "basketcase" found in the Florida Everglades, Clint Conklin's early-production No. 5R038 Shelby is used for both the street and open track, so it was crisply tuned from a recent outing at Road America. Clint's father, Fred, found and restored the car for 18-year-old Clint, who will get full use of it when he graduates from high school next spring. The Cobra version of the 289 High-Performance engine was recently rebuilt to factory specs with the exception of a smaller 600-cfm Autolite 4100 four-barrel in place of the original 715-cfm Holley. In its Road America open-track form, the GT350 was equipped with Dr. Gas X-pipes and open exhaust.

Although plagued at the start of our testing by a misfire, which was eventually diagnosed as a strange electrical glitch in the starter solenoid, Clint's GT350 ran strong on the Dynojet, even with the small four-barrel, producing 202 rear-wheel hp at 4,800 rpm. Factoring in a 17-percent power loss through the four-speed drivetrain, flywheel horsepower was estimated at 236, still 70 hp off from Shelby's 306hp rating.