Time does not stand still in the automotive performance world. Technology and competition never cease raising the bar to a higher level. What was good a decade ago is today’s also-ran. In the case of the Ford 429/460 big-block engine series, Ford Racing knew its existing nine-year-old aluminum Cobra Jet heads were facing serious competition from a number of aftermarket alternatives. It was time for an update that would incorporate modern technology, yet still work with most existing parts—so Ford had head maestro John Kaase at Kaase Racing Engines redesign the heads with a new combustion chamber configuration, revised valve angles, and subtle internal port alterations. Result: a new Super Cobra Jet (SCJ) head that should be available by the time you read this.
The head’s new heart-shaped combustion chamber maintains the CJ’s 72cc chamber volume, but the valves have revised angles that position them further away from the cylinder wall to reduce shrouding and improve flow. These new angles may cause piston contact, especially with big cams or near-zero deck heights. You may need to fly-cut a new valve notch on the intake side to correspond with the revised valve location.
The altered angles also mandate different pushrod guideplates and pushrods than previous 429/460 head designs, and—for the first time on Ford’s 429/460 big-block series—dissimilar pushrod lengths are needed on the intake and exhaust sides. Exact lengths will vary depending on the camshaft base-circle, the lifter type, the previous cylinder head and valvetrain configuration, and how much the block has been decked, but if upgrading from typical early Ford 429/460 heads with stud-mounted valvetrains or Ford Racing’s previous aluminum Cobra Jet head, Ford sources say pushrod lengths need to increase about 0.350 inch on the intake side and 0.600 inch on the exhaust side.
Despite these changes, the new heads still use the same 2.200-inch intake/1.76-inch exhaust valves, valvesprings, retainers, and standard 7/16-inch stud-mounted roller rockers as previous Ford Cobra Jet heads with adjustable valvetrains. Just as important, standard Cobra Jet-style intakes and exhaust manifolds or headers bolt on and current valve covers fit. Thanks to the redesign, Ford claims the SCJ heads are worth 40-50 hp over its previous aluminum Cobra Jet design when installed on a big roller-cammed 514 crate motor (Ford plans to make the changeover to the new heads soon). But what would the average car crafter see on a typical bolt-on 460 hop-up? To find out, we had Westech Performance, our favorite dyno-test facility, modify a 9:1 Ford 460 short-block that had been previously assembled with iron heads and a generic RV cam (about 0.545-inch lift and 220/228-degrees 0.050-inch tappet-lift duration). The iron heads were vintage ’68-’72 D0VE-C castings with 2.06-inch intake and 1.76-inch exhaust valves that unlike ’73-and-up heads at least have independent stud-mounted rockers and small 75cc combustion chambers. Although not up to modern standards, the early castings are considered a step up over commonly available ’73-’97 92-97cc large-chamber heads, which are said to have poorer-flowing ports and an inefficient, detonation-prone chamber shape.
First Westech stabbed in a modern, aggressive hydraulic cam profile—a Comp Cams Xtreme Energy 274, selected because of its excellent track record in last year’s big-block buildup series. The cam was complemented with a Hi-Tech double-roller timing chain, 1.7:1 Pro Magnum roller rockers, dual valvesprings, and appropriate pushrods and guideplates.
Union 76 91-octane unleaded was metered by a Demon 950-cfm carb atop an Edelbrock Performer RPM intake with a 1-inch spacer. With 37-degrees of ignition lead, the engine made a best of 464.8 hp and 512.3 lb-ft of torque with the iron heads and Comp bumpstick—up a healthy 20 lb-ft and 30 hp from the original RV grind. Not bad for a first pull, but now it was time to get ahead. On went the SCJ heads, complete with valves, the new-configuration guideplates, and Ford-supplied springs. Pushrod length was adjusted to achieve proper valvetrain geometry, but the deep-dish pistons used in our generic rebuilder short-block were so far below the deck at TDC that there was no need to fly-cut new intake-valve notches.
With slightly smaller 72cc chambers, the new heads raised compression about ¼ point over the iron heads’ 75cc chambers, but this slight gain was more than offset by the cooler-running aluminum heads’ greater heat rejection properties…so we believe the observed power and torque increase is primarily due to the new head’s chamber and port improvements. And what a gain it was! Even though the SCJ heads are really designed for big cams and high rpm, they still kicked ass on this relatively mild engine, gaining 46 hp and nearly 35 lb-ft of torque over the iron heads. Our mild-mannered engine was now thoroughly tuned up, generating 511 hp and 546.8 lb-ft at the peaks. Overall and average numbers increased significantly throughout the 3,500-5,600–rpm test range. All in all, a successful outcome. This is one swap you can’t afford not to pass up!
