How To Install Ported Stage V Heads - Stage V Booster Blast

Let's face it, production big-block cylinder heads aren't getting any younger. In 1978, the last Mopar big-block production engine was built, and that was almost 25 years ago. Moreover, the prized earlier #906 or #915 production cylinder-head castings are both well over thirty years old now. So, though designed as a performance upgrade in bracket or street performance applications in the 1980s, Mopar Performance's Stage V heads have been revised in recent years to double as a good service replacement head for the B/RB wedge.

The Stage V came into being, not surprisingly, as a replacement for the Stage IV performance head of the '70s. Unlike the radical Stage II and III Max Wedge production race cylinder heads, both the Stage IV and the Stage V were revised late-model passenger-car cylinder-head castings. The idea was to produce a performance head that could take all of the stock parts-valves, springs, and valvetrain-while working with the same intakes and headers as production heads.

These days, with more extensively redesigned heads such as Mopar Performance's Stage VI and Stage VI Max Wedge aluminum heads available, the Stage V has been targeted more towards the replacement market. After all, heads take a beating and wear out. Given decades of rebuilds and valve jobs, finding good used production head cores gets tougher every year. Also, a used set of original production heads typically need new guides, hardened exhaust seat inserts, a valve job, surfacing, and so on. The economics start to tip toward a fresh casting.

Indeed, priced at $375* each as bare castings, the Stage V may be the way to go from a cost standpoint alone. The bare casting, part # P4529993 (minus valves, springs, retainers and locks), is already finish machined with the seats cut for the popular oversize 2.14-inch intake, 1.81-inch exhaust-valve sizes. In addition, they include hardened exhaust seat inserts, a necessity in high load/heat applications with today's unleaded fuels. Between these two areas, there is a cost savings right off the top as compared to rebuilds. Assembled versions of these heads are also available.

Originally designed for the performance market, the earlier version of the Stage V came without an exhaust crossover. In keeping with the head's new role as a replacement piece, the crossover was put back into the current version. This allows the Stage V to be smog-legal in applications that use EGR, and also allows for the operation of the factory well-type automatic choke mechanism. In fact, the production-valve-sized (2.08-inch/1.74-inch) version of this head (P4529992) is an NHRA legal replacement for the original heads in Super Stock class racing. The Stage V's current role as a replacement head notwithstanding, it was originally drawn up as a performance piece, and these aspects of the head haven't been changed. The plan for this project was to get a baseline and port the heads for optimal street use.

A Heads-Up View
Compared to the production pieces, the differences in the intake port are subtle, starting with the more open port bowls of the Stage V. Farther down, the valveguide boss in the intake port is radically smaller than the long, intrusive boss found in the earlier '67-'70 #915 and #906 production castings. The later '71-'78 #346-#452 production castings also had a downsized guideboss in the intake, but they were still not as compact as the Stage V. As opposed to the flat roof and low shortside (the bottom radius of the port) found on the #346-#452 smog heads and Stage IV castings, the port roof and floor in the Stage V have been raised to the more desirable position of the #915 and #906 castings. The oil-feed hole to the rocker has been downsized from 7/32 inch to 5/32 inch, so the resulting bulge in the port wall has more meat in it for porting before hitting oil. Lastly, the port window at the pushrod "pinch" has been cast wider.