Magnum HeadsIntroduced in 1992, Chrysler's Magnum engines are the epitome of factory produced small-blocks. Available in 318 and 360ci displacements, these engines can be found in thousands of Dakota and full-size Dodge trucks produced from 1992 to the present. While the Magnum short-block remains very similar to the 318 and 360 engines of old, the cylinder heads offer some advantages that aren't seen in previous small-block cylinder heads. The combustion chamber of these heads offers a double quench area, capable of higher power output than factory heads of the past. These heads also offer large 1.92-inch intake and 1.60-inch exhaust valves and larger port size than the earlier swirl port castings, making them the best factory produced cylinder head for a performance build.
Magnum heads can be bolted onto your non-Magnum LA engine, but there are several differences you should be aware of. First, the 60cc chamber size of the Magnum head is likely some eight to ten cc's smaller than the chamber of the head you're replacing, so the compression ratio must be factored. Next, the Magnum head uses pedestal rockers instead of the tried and true shaft mount system of old. These rockers are a good design, but are oiled via the tappet and pushrod so they require that the lifters be changed to AMC units with oiling provisions. Pushrods also need to be changed to hollow units for the same reason. An additional difference is the angle the intake manifold bolt holes are drilled into the head. Magnum heads require that a Magnum specific intake be utilized, which adds cost. Head bolt length is also different from the older LA heads, so Magnum head bolts must be utilized as well.
Even with the differences it is well worth using the Magnum head for your performance or race small-block build. These heads are readily available and offer the best power potential of any factory-produced head. Intake manifolds and performance rockers are available from several aftermarket companies and really wake these cylinder heads up. Magnum heads also respond well to port and bowl work, making these heads an excellent choice for your next small-block build.
Aftermarket Small-Block Cylinder HeadsWhenever a car manufacturer designs a product that works as well as the Chrysler small-block, the aftermarket follows by offering products to improve performance for the enthusiast. Such is the case with the Chrysler small-block. Once limited to the X or J castings for our builds, we now can choose cylinder heads from Mopar Performance, Edelbrock, Indy Cylinder Head, and Brodix for our engine build. While aftermarket cylinder heads do cost substantially more than a factory head found in the scrap yard, the additional performance can be worth it. Chrysler engineers in the early '70s realized that one of the biggest limitations to the small-block head's flow was the design of the intake port. By relocating the pushrod holes, utilizing special rocker arms, and designing larger, oval intake ports, the W-2 cylinder head was developed for racing applications. This head is still produced and used by many small-block racers today.