First Look: Edelbrock's Magnum Heads

An upgrade with room to breathe.

It's not surprising Edelbrock has earned quite a name in the Mopar world with their cylinder heads--a combination of high-quality, reasonable pricing, ease of installation, and right-out-of-the-box performance delivered in the bargain. It's not a stretch to say Edelbrock heads have actually changed the way that performance Mopar engines are built. The cost effectiveness of their offerings has virtually made stock iron obsolete in applications where power and price are primary considerations--key factors in practically every engine we build.

Edelbrock is at it once again, this time with a new cylinder head designed as a replacement for the '92-and-up Magnum small-block architecture.

When the original production Magnum heads were introduced, it was a significant step up for small-block Mopar performance. While the early 340 "X" heads had set a high benchmark in the late '60s, by the early '90s there had been a long drought in high flowing production heads. The Magnums were quite a departure, and the new Magnum engines stepped power up considerably over what had been previously available. A large part of that production power increase was via the improved flow of the Magnum cylinder heads.

However, high flow was only part of the story in improvements with the Magnum small-blocks. The sealing of the intake manifold was improved, the intake was redesigned for vertical attaching hardware, and doubling the number of fasteners attaching the valve covers, eliminating the ever-present seepage through the valve covers. The dead space of the old-fashioned relieved open combustion chamber was finally gone in favor of a head with abundant squish/quench areas via a closed chamber. The exhaust port was streamlined, at last doing away with the horrible shape of the earlier ports and the useless "dog-leg" of the center two port exits. Of all the changes incorporated with the Magnum, the most dramatic was in the valvetrain.

The LA-series small-block had always used shaft-mounted 1.5:1 ratio rockers, feeding oil from the cam bearing journals through passages in the block. This block passage met the heads, which routed the oil via a gallery between the intake ports leading to the rocker pedestal, and, ultimately, into the shaft and to the rockers.

The Magnum valvetrain is totally different. The rockers were up-rated to 1.6:1 ratio for higher lift and are individually mounted on paired pedestals. The valvetrain is lubricated via the lifters through hollow pushrods. The system proved to be bulletproof. Traditionalists were upset with the change from shaft-mounted rockers, but, in reality, that system was also very good. However, the shaft-mounted rocker's real performance advantage only comes into its own in very high-output configurations, utilizing offset rockers, as Chrysler exploited with the T/A and W-series heads.