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Some things may apply to engines in general
By Steve Baur


428 Cobra Jet blocks are getting harder to find these days and usable cores even harder. Many of these have been beaten on for years or left to rust in a junkyard. This particular block had several cracks in the main cap area that were revealed upon magnafluxing. This is a common problem with the 428 CJ blocks and something that was easily repaired.


While most FE engine blocks are similar in appearance from the outside, many details on the inside can reveal their true identity. These heavy main webs are a 428 CJ feature designed to add extra support to the main bearing saddles.


Even with the heavy main bearing webbing, cracks have formed in this area that needed to be repaired. To provide additional strength, a steel main girdle was purchased from eBay. Manufactured by Concept Design Engineering, this girdle ties the main caps together and it also ties them to the skirt of the block.


Once the block was repaired, the machining processes could begin. Competition Motorsports uses a BHJ fixture to machine the deck surface. This squares the decks to exactly 90 degrees of each other and brings them parallel with the cam tunnel and crank centerline.


Here’s where the cylinder sleeve meets the bottom of the block. Normally, there is a natural chamfer at the bottom, but Mike Broadway of Competition Motorsports prefers to square this off so the sleeve rests on it. The idea is that it helps hold the sleeve in place and it provides an overall increase in strength to the block.


There are a number of areas that benefit from opening up the oil gallery entry and exits in the block. This is the oil filter boss on the block, and opening the galleries up offers better port alignment and better flow. Remember to modify the gasket here as well.


Due to core shift and manufacturing tolerances, the main bearing oil gallery openings do not always line up. Just as the oil filter and oil pump ports are port matched, this is done to the main bearing oil galleries as well.


The full-groove on the main journals has been in use since the ’60s. It supplies an abundant amount of oil to the mains and both Clevite and King offer the correct grooved bearings for this 428 CJ application.


Since drag cars do not require that much in the way of engine cooling, many racers opt to fill the bottom half of the block with a solid block filler. Often referred to as concrete or cement, this substance is a cement-based, specifically manufactured product that fills the water jackets and solidifies to strengthen the block. As you can see from this picture, it’s usually the bottom half of the engine block that is filled so as to still provide a suitable amount of coolant circulation.


The cylinder heads for this build are casting number C8OE-N, specified as 1968-70 428 Cobra Jet cylinder heads. The NHRA’s minimum combustion chamber size is 68cc, and these particular ones measured in at 68.4. The intake port measures 2.34 x 1.34 inches and the exhaust port measures 1.84 x 1.34 inches. No porting is permitted in Stock Eliminator — some more nefarious racers opt for illegal acid porting. This process opens the ports up while leaving a factory cast look. We don’t need any drama with this build.


Due to the 428 CJ cylinder head’s relatively small size, it can be prone to distortion when machined, so Competition Motorsports performed all of the headwork with the cylinder head fitted to a torque plate. “It’s a relatively small piece to begin with, plus you’re dealing with a head bolt torque around 90-100 lbs-ft,” notes Competition Motorsports’ Mike Broadway.


The combustion chamber cannot be modified, but you can modify the angle throat and top angle of the valve seat. The sealing angle must be stock. Factory valve sizes must be used and these come in at 2.080 inches on the intake and 1.65 on the exhaust.


Connecting rods and pistons are stock or stock based and must meet a minimum weight for the combination. This build utilizes stock connecting rods (blueprinted) with ARP hardware, as well as the NHRA-spec Venolia piston. The piston is sized for a .030-inch overbore and features the stock 10.25cc dish. Per the rules, a piston skirt coating is permitted.


The NHRA specifies a piston ring groove size, but not a size for the ring itself. To take advantage of that, thin, low-tension rings like these from Total Seal are used in conjunction with spacer rings that do not scrape the cylinder wall, but take up the necessary space in the groove. You can see the difference in width between the tension ring in the middle here and the spacer ring below it.


COMP Cams provided the valvetrain for this build, including this hydraulic flat tappet camshaft. The hot Stock Eliminator-spec bumpstick (Grind card number 25642814) offers 258/266 duration at .050, a valve lift of .527-inches, and an intake centerline of 106 degrees.


These are the COMP Cams 428-spec hydraulic lifters for this application (834-16), but when it comes to building an engine to a specific set of rules, each engine builder will prefer to tweak things as much as they can. As such, Broadway prefers to use a 302 lifter, which is permitted by the rules, and make his own modifications to them. While we can’t tell you what those entail, we can tell you that the 302 lifter is a taller lifter than the 428 one, and that its extra height reduces the pushrod length, which helps stabilize the valvetrain at higher rpm.


COMP also supplied the build with a set of its beehive valve springs (26120-16), steel retainers (1795-16), cup seats (4697-16), super locks (616-16), and a timing set (310. The beehive springs are the latest in technology and offer a reduced weight and better high-rpm stability. The shiny aluminum spacers on the shaft are vintage Holman-Moody parts that replace the factory coil springs to provide more stable rocker arm geometry. These are legal per the NHRA, as are aftermarket roller rocker assemblies.


If you’re looking to set a record, there are some aftermarket stepped-primary headers out there for this application. However, given this build’s budget-minded approach and slightly less ambitious aspirations, Hooker Super Comp long-tube headers are to be used. These feature 21/8-inch primary tubes that meet at 3.5-inch collectors. The rather aggressive turn down from the cylinder head exhaust port is necessitated by the confines of the Mustang engine bay.


You certainly don’t want to use a stock harmonic balancer when racing, so we called up Innovators West and ordered the company’s FE Ford seven-inch harmonic balancer (20 and crank spacer, which retail for $375 and $50, respectively. The Innovators West balancer is SFI-18.1 certified and features a lightweight aluminum case, stress-proof steel hub, and 1040-steel inertia rings for durability. It can be used on both street and race engines, it accepts stock three-bolt accessory pulleys, and it is designed for stock length crankshaft snout.


Wrapped up with a stock cast-iron intake and vintage 428 Cobra Jet valve covers, this now 433ci dinosaur performed admirably on the Competition Motorsports dyno. Expectations were set at 480 hp, while hopes were clamoring for 500. Successive runs of 493, 500, and 502 horsepower were seen using the stock-spec, but blueprinted, 735cfm Holley carburetor. Torque was equally impressive at 477, 488, and 491. Every run produced better results, and there will be further tests with the Quick Fuel Technology carburetor and the roller rocker arm assemblies that are waiting in the wings.


Quick Fuel Technology SSR-780-VS carburetor


Quick Fuel Technology SSR-780-VS carburetor





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Difficulty Rating: Professional help recommended Time factor: Days

It’s no secret that muscle cars were built for speed, but unfortunately many of them today see full-time duty as parking lot ornaments at car shows.

Thankfully, there are racers across the country that flex that big-block muscle on a weekly basis and allow these legendary vehicles to do what they do best.
NHRA Stock Eliminator has been around as long as the muscle cars themselves and here among the ranks of these dedicated and hardcore index racers you’ll regularly find the legends of the ‘60s muscle car movement. Within Stock Eliminator, there are all sorts of vehicle makes and models, each packing potent engine combinations that make the most of a relatively strict rule set. Building an efficient chassis is essential — after 50-plus years of competitive development, there aren’t many stones left unturned on the engine front, though engine builders continue to try.
When we heard about an engine rebuild on a legendary 428 Cobra Jet coming up, we decided to tag along to see what goes into one of these Stock Eliminator combinations — or rather what doesn’t!
Said 428ci engine had propelled Port Richey, Florida’s Rusty Gillis and his 1969 Cobra Jet Mustang into the low 11s in the quarter-mile back in 1998, but the last trip to the track had the Cobra Jet powerplant belching smoke and more as it returned from its last run.
That sort of performance isn’t befitting of a car that was a former SS/GA record holder in the ’70s. With that sort of pedigree, any new build needed to be a step up. While the last engine was estimated to make in the neighborhood of 450 horsepower, the plan and hope for this rebuild is to be more competitive (480-520 hp) while maintaining a sizable margin of safety and longevity, all on a reasonable budget. Top-of-the-line Stock Eliminator engines can cost north of $40,000, so it’s important to have an idea of what you plan to do with the vehicle before you get started.
Handling the engine build for Gillis is Mike Broadway of Competition Motorsports in Sarasota, Florida. Broadway has a long history of building competitive racing engines across a variety of racing applications. An avid Ford enthusiast, Broadway’s most recent customer build is a high-winding, 8,000 rpm-plus Boss 302 that sees regular duty in vintage road racing. Broadway is no stranger to big-block FE engines either.