Ford really got it right with the 1968 428 Cobra Jet (CJ). Technically a midyear offering, the 1968 1/2 CJ combined 427 Low Riser heads, a cast iron copy of the aluminum 390 Police Interceptor intake manifold, the 390 GT’s hot hydraulic cam, a healthy 735-cfm Holley four barrel, and streamlined exhaust manifolds to fight off the 396s, 440s and 400s from the competition. Best of all, unlike the fire breathing 427 FE (which was mostly installed in fullsize 1963-1967 models), the 428 CJ was commonly available in all the popular midsize Ford-Mercury muscle models. More than 18,000 were installed in 1968-1970 Mustangs alone.
But there was one thing about the 428 CJ that left everyone puzzled. The factory power rating seemed to be a typo. Without a wink or a nod, Ford claimed the new CJ made 335 hp at 5,600 rpm and 445 lb-ft of torque at 3,400 rpm. While the torque claim was in line with expectations, many wondered why the big 428 CJ was only 10 ponies ahead of the 325hp 390 GT four-barrel mill. Beyond that, the so-called Thunderbird 428 offered in fullsize Fords and T-birds made 345 hp, 10 more than the CJ despite its milder cam, low-rise iron intake, 446-cfm Ford 4300 series four-barrel carburetor, and clunky log-style exhaust manifolds.
The facts became clear once 428 CJ Mustangs and Fairlanes started running high 13s at the strip with zero preparation. The 335hp rating was nothing more than a ploy to distract the NHRA from the CJ’s true ability, in hopes of getting more advantageous classifications in Stock and Super Stock competition. Because the NHRA used advertised factory horsepower and shipping weight claims to group vehicles into competition classes and categories, it paid to fib a little bit; 428 CJ-powered Mustangs and Fairlanes quickly became feared street and strip machines.
As with most deceptions, the ruse was quickly unmasked as the NHRA factored the 428 CJ into higher classes so it couldn’t bully weaker machinery. Oddly, however, Ford never revised the sandbagged horsepower claims. Right to the end in 1970, the 335hp rating stuck. So the question remains, how much horsepower does a stock 428 CJ really deliver?
To find out, we visited Donnie Wood and his team at R.A.D. Auto Machine where a Q-code (non Shaker) 1969 Mach 1 428 CJ was being rebuilt to stock specifications. We could tease you and save the punchline for the end of the story, but we will save you the disjointed experience of leafing ahead by reporting that it delivered 365.1 hp at 4,800 rpm and 452.4 lb-ft at 3,700 rpm on the R.A.D. Land & Sea dynamometer. Given the CJ’s reputation for being underrated by Ford, the 30.1 extra ponies weren’t a big surprise. Let’s dig in and see what makes the 428 Cobra Jet tick.
1 R.A.D. bored the cylinders 0.030 over on a Rottler F79A three-axis CNC milling station to clear up minor wear. The main bearing saddles and caps were align honed.2 The fingers point out oil galley cap plugs, which must not be overlooked during block cleaning and assembly. Another plug is present near the distributor mounting boss.3 While Ford offered forged-steel cranks in the 427 family, the cost-conscious 428 uses a cast-iron unit with a 3.98-inch stroke. R.A.D. removed 0.020 inch from the main and rod journals to restore fresh surfaces. Main bearings are Sealed Power (PN 4261 M20), as are the rod bearings (PN 8-3230CP-20).4 Designed long before the advent of one-use, torque-to-yield fasteners, the 428’s main cap bolts are tightened to 100 lb-ft in two steps. The standard two-bolt main caps are totally adequate for all but the most extreme naturally aspirated applications.5 The 428 shares its 6.488-inch-long forged-steel connecting rods with the 390 except for one important difference: 11/16 fasteners versus 3/8. The larger-diameter bolts/nuts (in the center of the photo) weigh 16 grams more per rod and can cause high-rpm vibration if carelessly mismatched. R.A.D. replaced the Ford hex nuts with 12-point ARP units tightened to 52 lb-ft.6 The stock-spec 428 cast pistons were replaced by Sealed Power forgings (PN L2303NF-030) with floating pins. At 840.5 grams, each piston is 19.4 grams lighter than the stock castings removed from the engine. Compression remains at 10.5:1. Rings are Hastings moly-faced units (PN 2M-595-030), gapped at 0.019 inch. The 427 was the only FE engine factory equipped with forged pistons.7 With its abbreviated intake port architecture, each FE head weighs a mere 39 pounds (bare). The 428 CJ’s C80E heads have as-cast (nonmachined) 73cc combustion chambers and 2.09/1.65 valve head diameters. The seats were in good condition so R.A.D. recut them instead of resorting to insert replacement surgery.8 Stock-diameter 2.09/1.65-inch valve sizes remain, but R.A.D. upgraded to 427-style swirl-polished stainless units from Engine Pro (PN 01-2300-8). The pen points out the abrupt stem-to-head transition of the stock valve. The streamlined valves add modest gains to flow.9 The stock valve-guide bosses accept most double valve springs without diameter reduction machining. R.A.D. revived the guides with bronze wall inserts. The exhaust seals are rubber umbrella-type (in fingers), while the intake seals are smaller PC style units with spring-loaded lips. They better prevent suction from drawing oil into the intake ports.10 To match the stock-spec camshaft, stock replacement single-valve springs (with flat-dampers) deliver 85 pounds on the seat and 300 pounds at 0.500-inch lift. Outside diameter is 1.812 inches, and stock stamped steel retainers and locks are employed.11 Aiming to replicate a stock 428 CJ driving experience in the restored Mach 1 host vehicle, hotter camshaft profiles were shunned in favor of this Howard Cams CJ clone (PN 257611-10). Specs are 0.481/0.490-inch lift, 256/256 degrees duration (advertised), 200/200 degrees of lift (at 0.050 lift). Like all (non 1966 Police Interceptor) 428 cams, it uses hydraulic lifters.12 Thicker Fel-Pro head gaskets (PN 8554PT) have a crushed thickness of 0.042 inch. They trim the 10.5:1 compression ratio by approximately a quarter point for added safety with modern 93-octane unleaded pump gas.13 The pen points to the integral air injection passage found in all CJ heads. Part of Ford’s Thermactor emissions control system, the threaded holes accept air injection piping to increase post-combustion exhaust gas temperature to burn off residual hydrocarbons before they exit the tailpipes.14 With its nonadjustable rocker arms, simple 9.59-inch long, 5/16-inch-diameter pushrods with ball-ends actuate the valves. FE builders must remember to install the pushrods after the intake manifold goes on because several of them pass through the manifold. Naturally this tip excludes the 427 SOHC, which eschews pushrods and lifters.15 The pen points to the rocker arm shaft’s oil squirt holes. They must be targeted inboard toward the engine centerline during assembly of the rocker arms. Failure will result in oil-starved rocker arms and scuffed valve guides.16 With the pressed steel oil deflector plates in position, the completed rocker arm units bolt to the heads. Note the cast aluminum rocker shaft stands that the 428 shared with lesser 390, 352, and 332 engines. The high-performance 406 and 427 engines came with stronger cast iron stands, which should be used with extreme valve spring pressures and radical cams.17 Like all FE engines, the 428 has an unusually long crankshaft snout. Its only drawback is a tendency to fracture when loaded with a crank-driven supercharger. Notably absent here is the “hatchet head” crankshaft weight seen on 1969-1970 428 Super Cobra Jet (SCJ) engines. Their heavier 427 LeMans-type cap-screw rods require the added mass (plus a specific flywheel/flexplate) to achieve balance. SCJ engines were installed in 1969-1970 when the Drag Pack, with its 3.91 or 4.30 axle ratio, was chosen.18 The benefit of the FE engine’s abbreviated cylinder heads is obviated by its husky intake manifold. R.A.D. Auto Machine’s Steve Chmura poses a 23-pound 427 aluminum intake manifold next to the CJ’s 85-pound cast iron unit. In a nonresto build, swapping the stock iron heads and intake for aluminum replacements chops a quick 100 pounds off the nose of any FE-powered car.19 Each of the 18,049 428 CJ Mustangs built in 1968-1970 (Mustangs only, this figure excludes thousands of additional Mercury and Ford Shelby, Fairlane, and Torino applications) inhaled through a 735-cfm Holley four-barrel. The 446-cfm Ford-Motorcraft four-barrel used on non-CJ 428s pales by comparison. Stock jetting specs were maintained for the dyno test with satisfactory air/fuel ratios.20 Built half a decade before Mustang’s 1975 switch to electronic ignition, all 428 CJ’s came with a single-point distributor. Fully capable of handling the 6,000-rpm ceiling, total timing is set at 35 degrees BTDC, all in by 2,000 rpm. Spark plug wires are date-coded reproductions from Marti Autoworks (PN SPW-11D 4Q67).21 Oddly mismatched to avoid the Mustang/Fairlane spring towers, the CJ exhaust manifolds are still an improvement over the small-outlet logs supplied on 390-powered Mustangs. Weights are 16.4 pounds (driver-side, bottom) and 19.0 pounds (passenger-side, top).
RPM
Torque (lb-ft)
HP
2,600
409.5
200.9
2,700
418.4
214.9
2,800
427.5
228.0
2,900
434.1
239.8
3,000
439.4
251.0
3,100
442.3
261.1
3.200
444.4
270.1
3,300
445.7
280.1
3,400
448.1
290.1
3,500
451.0
300.6
3,600
452.2
310.0
3,700
452.4
318.8
3,800
452.0
327.0
3,900
449.0
333.4
4,000
444.8
338.8
4,100
440.9
344.2
4,200
436.6
349.2
4,300
431.8
353.5
4,400
425.4
356.4
4,500
418.7
358.5
4,600
412.9
361.5
4,700
406.7
364.0
4,800
339.4
365.1
4,900
390.7
364.6
5,000
376.5
358.9
22 Though some claim the 428 CJ actually made in excess of 400 hp, we observed 365.1 hp at 4,800 rpm, almost 10 percent more than advertised. After some break-in miles, we’d likely see 375 hp and, with headers, yes, very likely 400 ponies. The peak torque of 452.4-lb-ft at 3,700 rpm is also higher than Dearborn’s claim of 445 lb-ft at 3,400. With more than 400 lb-ft available from 2,600 to 4,700 rpm, the Mach 1’s tail is sure to be obscured in clouds of tire smoke.
No April Fool: The 427’s Last Stand
Before being replaced by the April 1, 1968, arrival of the 428 CJ, the mighty NASCAR-inspired 427 gave one last gasp in detuned form. Identified by the letter W in the fifth spot of the VIN, this early 1968 edition was the only 427 with hydraulic lifters, an iron intake manifold, a single point distributor, a smog pump (Ford’s Thermactor system), an automatic transmission (the four-speed was not available with the 427), and optional air conditioning. It was probably a case of “building out” soon-to-be obsolete 427 inventory. The W-code 427 and 428 CJ shared just about everything except main bearing caps and bore/stroke dimensions. Common to both were vital details such as camshafts, intake manifolds, valve and port sizes, and compression ratios.
The big difference was the price (at $622, the 427 cost $188 more than the $434 428 CJ), transmission availability (the 427 was only teamed with the C6 automatic), carburetors (the 427’s single Holley four-barrel rated 600 cfm, 135 less than the 428 CJ), and rated output. The 427 boasted 390 hp, a full 55 more than you-know-who.
The immaculate 1968 427 seen here powers Craig Keith’s Cougar XR-7G and resides in West Brookfield. Massachusetts.
