THE  FORD 289  K CODE HIGH  PERFORMANCE ENGINE

 In June 1964  the HI-PO engine, as it was known, became a Mustang production option at about $325.00. The fifth character of the VIN is the letter K in these cars, hence the name K code. There are a few  64 1/2 HI-POs which are generator equipped (the distinguishing feature). The engine was rated at 271 @ 6000, 312 @ 3400. 64 HI PO Comet below.

The HI-PO engine was also offered as a production option in 1966, and again (for the last time) in 1967. By then the  more popular  big blocks were taking over as sales favorites. Because of the potential racing applications of the 271 HI-PO engine and to limit factory liability, Ford warranted the HI-PO engine for 90 days / 4,000 miles. All other Mustang engines came with a standard 1 year / 12,000 mile warranty. The option package included special suspension and 6.95 x 14 dual Red Band tires. These tires were part of the reason that road test figures show high 14 second quarter mile times. These were inadequate, skinny bias play tires that evaporated in smoke the minute the power was turned on. Better tires and a good rear axle produced high 13 second times.

Production Figures

1965  7,273 of the 680,989  Mustangs built 

1966  5,469 of the 607,568  Mustangs built 

       1967  489 of the 472,121 of the Mustangs built 

The engine began life as a standard 289 cast iron block. Unverified and an area of controversy is the crankshaft. It is said that the crankshafts were tested for hardness and ones that met a standard were  picked for the HI-PO engine. The remaining cranks  went into standard 289 engines. The rod bearings and bolts were upsized. The front of the crankshaft has a hatchet weight to balance out the weight of the larger rod bearings and bolts. The harmonic balancer was also enlarged for the same reason. Pistons were cast, and the compression ratio was 10:5 to 1. The alternator pulley was also enlarged to reduce the number of revolutions at high engine RPMs. HI-PO engines also had a metal radiator shroud, and a wide four blade, riveted cooling fan. 

The cast iron heads were unique to the HI-PO engine, with chrome plated valve stems, solid valve lifters, screw in rocker studs, and cast in valve springs guides. The camshaft has special contoured lobes for high lift valve openings, and contributes to the slightly uneven idle and that unique solid lifter sound. The exhaust manifolds were cast iron free flowing 'header type' and all HI-POs had a 2" exhaust system with a crossover H pipe to equalize pressure and dual  low restriction mufflers. The sound was amazing; a friend of mine had one of these Mustangs, and everybody thought it had a 427 under the hood. His had a Cobra kit with 3 x 2 barrels and a hotter cam, rated at 343 hp.  Believe me, this car was an animal. Easy high 12 second quarter mile times.

The intake manifold was a standard cast iron 289 4V, but the carburetor was a 600 CFM Autolite (Holley) 4100 with a manual choke and a tuned 360 degree low restriction air cleaner. The distributor was a Ford dual point with mechanical advance, ignition wires were solid core, and the spark plugs (in 1965) were Autolite BF-32s. The BF-32s were a fairly cold spark plug that occasionally fouled in normal driving and BF-42s (slightly hotter) spark plugs were specified for later 1966 & 1967 engines.

The transmission was a Ford close ratio 4 speed cast iron top loader with a 10.4" clutch. This was a mandatory option with the 271 HI-PO engine in 64 1/2 and 1965. In late 1966 and in 1967 an automatic transmission was  available. The rear axle was the Ford 'unbreakable'  9" ring gear in ratios of 3:50, 3:89, and 4:11. Traction lock rears were available from 1966 on. Traction lock was not available in 64 1/2 or 1965 Mustangs. 

Heavy duty suspension (front / rear springs & shocks) with a larger (13/16") front sway bar was included with the HI-PO engine option. This was the same 'Special Handling Package' offered in the V8 'GT' option cars. Tires were 14" dual redlines standard with a no cost option of blackwalls or whitewalls. The steering was the fast ratio box (16 to 1) used with the power steering cars, but without the power assist. Power steering, power brakes, and air conditioning were not available from the factory on the K-Code HI-PO. 

The HI-PO engine was used in modified form by Carroll Shelby for the 1965 -1967 Shelby GT350, raising rated power to 306 hp @ 6000 rpm through use of special exhaust headers, an aluminum intake manifold, and a 715 cfm carburetor. The Shelby engine also had a larger oil pan with baffles to reduce oil starvation in hard cornering. Shelby also replaced the front press-in oil gallery plugs with screw-in plugs to reduce failure.

From 1966 to 1968, Shelby offered an optional Paxton supercharger for the 289, raising its power (on Shelby GT350s) to around 360 hp. One prototype was made in July 1965 and recently sold for over $500,000.00 Below is one of 11 1966 Paxton equipped cars, this one in Ivy Green, also a prototype car.  Factory invoices show that 28 cars were shipped with factory installed Paxton superchargers in 1967. In 1968, the Paxton was again offered on the 302 V8 which now powered the GT350. Few were ordered, as the big block models proved more popular.

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