When Edelbrock introduced their Mopar small-block heads a couple of years back, they filled a sorely needed void in the Mopar performance marketplace-an affordable, bolt-on, high-flow replacement for the production passenger-car cylinder head. The head quickly became a popular choice with Mopar fans looking to build that special engine, but one question remained: When would they come out with a version for the big-block? After all, you could get the small-block with decent-flowing production iron heads, but making real power with the big-block was always a challenge with the relatively flat-flowing stock heads.
It takes a lot of airflow to feed 440-plus cubic inches, and Chrysler big-blocks needed serious improvement in cylinder-head flow. So the factory created a series of big-port high-flow heads for the Max Wedge. In 1964, the introduction of the Hemi was really an adaptation of the highest-flowing cylinder heads the engineers could conceive for the existing (but improved) RB Wedge. With the release of the Hemi, continued effort on serious high-flow wedge heads became irrelevant. The heads used on the famous 383 and 440 Magnums from the musclecar years were nothing but the very same heads used across the board on all big-block engines (except on '67 440s). That's essentially a one-size-fits-all head, from a 383 two-barrel in a four-door Polara, to the 440 Six Pack in a '69 Super Bee.
To fulfill such broad requirements, the production cylinder heads necessarily became a compromise. In the context of the time, it wasn't really a bad compromise. The biggest production cams in the 383s and 440s only lifted the valve some .450 inches, and the production head offered reasonable low- to mid-lift flow. Turn up the heat, however, and the heads become the limiting factor. Making big power with production iron heads requires porting, and competent porting at that. We thoroughly researched 440 production head mods in previous articles to get the information out there. Unless you have time, patience, and a sculptor's touch, be prepared to pay big for a set of fat-flowing old iron. We don't know any porters who work for free, and with the time involved to really get the stock heads to move air, we're talking $1000-$1500 worth of cutting. Add the cost of 16 new valves, springs, retainers and keepers, a high performance valve job, guides, machining the spring seats if a large cam is used, a set of hardened exhaust inserts, and we're talking serious dough for a really good set of iron heads.
Edelbrock has developed a line of high-flow aluminum cylinder heads for a broad range of applications, but until now the big-block Mopar version has been conspicuously absent from the lineup. The Edelbrock approach is to design the head as true to the concept of a bolt-on replacement as practical, retaining the production layout so items such as the valvetrain, intake manifold, and headers will interchange with those designed to work with production heads. This constraint makes it more difficult to design a head that offers meaningful improvement in airflow; however, it dramatically lowers the cost of making the transition from the production head to the aftermarket Edelbrock head.
Since the basic layout is similar to the production piece, the design and execution are critical to achieving high flow. With the resources of Edelbrock's high tech research and development (R&D) facilities, design engineers are able to create the basic port profiles using computer models. Through stereolithography, the electronic information is transferred to a tangible working prototype of the port. The prototype comes in the form of a laser-cut full-size plastic model, called a flowbox, that gives the design team a port that can be easily tested for flow performance. Evaluation at the flowbox stage can be incorporated into the design before any real metal castings are poured.