Eric English
June 2, 2014
Photos By: Source Interlink Media Archives, Bob Mannel

Somewhere on the heels of celebrating the Mustang's 50th birthday, we find it appropriate to commemorate that same half century mark for the iconic pony's very first high performance engine—the 289 High Performance. Of course most of us lovingly refer to it as the Hi-Po 289, and it played a huge role in putting Mustang on the roadmap for real car lovers across the land. Available within a couple of months of the April 17th Mustang debut, and lasting through 1967, it was this engine which made Mustang more than just a pretty face; more than a sporty looking secretary's car. Simply put, the Hi-Po 289 literally transformed Mustang into a true performance machine.

Before we go any further, let's be quick to acknowledge the 289 High Performance's debut in the Fairlane during the 1963 model year. From that perspective, the Hi-Po has already crested the half century mark. Since our focus here is Mustang-centric, perhaps we'd be better off framing our celebration story as a “Happy Birthday Hi-Po Mustang”. From this perspective, we remind readers that all Hi-Po Mustangs carry a K as the fifth digit in the VIN, thus the “K-code” description often seen.

Nineteen sixty seven was the last year for the K-code Mustang, and with in-house competition from the newly available 390 big-block GT, very few were produced. Kevin Marti’s data shows that just 489 were built, and unlike in earlier years, the GT (or GTA) package was required. This is Gary McKay’s incredible K-GTA convertible—one of just 50 droptop Ks built for 1967—16 of which were GTAs.

The Hi-Po strutted its 271 horsepower stuff with heavy duty engine components, mandatory four-speed transmission (until 1966), and a tough as nails 9-inch rear. The beefier engine components were present top to bottom, what with a solid lifter cam and associated valvetrain, larger two-bolt main caps, better connecting rods, and a high nodularity iron crankshaft. Add in a dual point distributor, Hi-Po specific exhaust manifolds, and a host of smaller supporting cast members, and you had a balanced package all the way around.

The automotive press of the day was impressed—although multiple magazine drag tests in the mid-high 15s aren't much to write home about today. Arguably the downfall of the Hi-Po was too few cubes, a low-rise induction package shared with the A-code 225-horse engine, and the same small valve sizes common to all sixties-era Mustang 289 and 302 small-blocks. Yet helping make the whole thing work well was the lightweight nature of the new Mustang, owing to its economical Falcon roots. You simply don't need huge power to smartly move 3,000 pounds, and that lithe weight also does wonders for cornering and braking. Carroll Shelby capitalized on all this with his GT 350, born from K-code chassis' and bolstered with some of the goodies Ford left on the table. Namely we're speaking of the hi-rise aluminum intake, Holley 715-cfm carb, Tri-Y headers and voila, you've gone from an advertised 271 horsepower right up to 306. Better than 1 horsepower per cubic inch was still pretty heady stuff in 1965.

Race versions of the Cobra and GT 350 were often around 350 hp with a single four-barrel—take for instance a GT 350 R-model engine. Such Hi-Pos did get improvements in the cylinder head department, what with larger valves (1.875/1.60-inch) and porting, more camshaft, bigger headers, etc. Dual quad or Weber induction, when allowed, made for even more power. In the end though, it's the street versions of the Hi-Po Mustang which have made it the legend that it is. Sure, there were plenty of faster cars in a straight line, more solid and luxurious muscle cars, and cars with a more pure and distinct sports car persona. And yet none of them ever sold like a Mustang, and none had the broad popular following. Mustang hit all the buttons for a vast base of people, with a pretty face, economical price, and a fun to drive demeanor led by none other than the K-code 289. So Happy Birthday Hi-Po Mustang—and a toast to another fifty!

This is a “factory correct” engine compartment, but sharp eyes will no doubt wonder how that can be. Whether in a Fairlane or Mustang, Hi-Po 289s weren’t available from the factory with air conditioning, right? True, but one could argue that there were four legit exceptions, including the one here. This is the engine compartment of Len and Linda Perham’s ’66 GT 350 convertible. That’s right; the four very special and unique ’66 GT 350 convertibles were all fitted with A/C at Shelby American.

Hi-Po Values

We hate to broach the subject of Mustang values in general, because there are so many variables. K-code Mustangs are no different, with wildly varying advertised and selling prices. Just one example can be seen in the results of the 2014 Barrett Jackson auction at Scottsdale. Mining the sold results from the auction on the Barrett-Jackson website (www.barrett-jackson.com), we found lot number 1565, a K-code/four-speed '66 Mustang GT convertible; Candyapple Red over black pony interior (original colors) which sold for $49,500. Likewise the same auction sold lot number 966 for $84,700, which seemed a virtual twin in terms of option—body style, colors, drivetrain, etc. save for a claimed 125K fresh restoration. Having never laid eyes on either, it's hard to opine, but one was clearly nearly twice the money.

We perused NADA and Hagerty classic car value websites, and found interesting numbers, along with some head-scratching discrepancies. For example it's possible on the NADA site to equip a '65 Mustang with a 390, and to arrive at an estimated value for such. On top of offering a combination that never existed, the ever-popular 200 hp 289 option is noticeably absent. With Hagerty it seemed the value calculator didn't understand that a base '65 or '66 Mustang could be optioned with a 271hp 289, limiting the option to a Mustang GT. Yet regardless of the omissions/errors of either, we offer the following examples of pricing from both sources:

NADA, 1965 Mustang (non-GT) (High Retail) 225hp 289 271hp 289
Hardtop 36,750 $41,160
Convertible 57,500 $64,400
Fastback $57,250 $64,120
NADA, 1965 Mustang (non-GT) (High Retail) 225hp 289 271hp 289
Hardtop 36,750 $41,160
Convertible 57,500 $64,400
Fastback $57,250 $64,120

Production Data

We've explained in the past how Kevin Marti's exhaustive Ford database begins with the 1967 model year, and when it comes to '67 Mustang K-code cars, the records show just 489 were built. Unfortunately in the absence of data for the '64½-'66 model years, production numbers are vague at best. Some hard numbers float around in certain books and internet sources, but an explanation for the data source is always missing, and we discount those numbers because of it.

To get some idea of how many '64 ½-'66 Hi-Po Mustangs might have been made, we turned to Bob Mannel, who literally wrote the book on all things 289. His monstrous “Mustang and Ford Small Block V8, 1962-1969” from RPM Press, is a minutia laden tome that is a worthy addition for any sixties-era Ford fan (www.fordsmallblock.com). Bob also runs the Hi-Po Fairlane Registry, and so we figured if anyone had some good ideas about how many K-code Mustangs were built, Bob would be a good bet. All of that said, Mannel is quick to emphasize his guesstimates are based on educated extrapolations of data, and should certainly not be viewed as hard and fast. Nevertheless, his insight gives us something to consider. Not including GT 350s, Bob believes around 600-800 K-code Mustangs were built for '64½, 3,500 for '65, and 2,500 for '66. This is based on familiarity with how many Hi-Po engines were manufactured, how many Hi-Po engines Ford generally produced each month, how many went into Fairlanes and Cobras, and other factors. Bob would love for conclusive numbers to be discovered some day, but until that time…

Seen here are two of the very worthwhile upgrades which Shelby American applied to the Hi-Po 289 for GT 350 production. Holley’s 715-cfm carb atop a Cobra lettered aluminum hi-rise intake. The Holley used vacuum secondaries and Le Mans style bowls.