This is your stock replacement for 1992-2004 V8 Magnum's
INTAKE RUNNER VOLUME 172CC
COMBUSTION CHAMBER VOLUME 62CC
INTAKE VALVE 1.920" EXHAUST VALVE 1.624"
This is our Magnum head that uses all Magnum rocker parts with LA style intake bolt pattern.
Chrysler 318 and 360 cylinder head built from a MAGNUM casting that has been drilled for a early intake manifold bolt pattern.
Retrofitting an LA engine to a Magnum configuration is amazingly straight forward, requiring no special modifications, just the right parts. Naturally, the Magnum heads are needed, and to attach them to the block, specific Magnum fasteners are needed. Mopar LA small-block heads are attached with 10 bolts each, with four short ones and a long one under the valvecover, while the Magnum bolt set uses five long ones in these positions. The stock fasteners are available (order part number HB318N. The production Magnum head gasket is a unique design, however the changes from the LA series are primarily to corral the pushrods into position during assembly. Regular LA engine gaskets can be used here.
As noted earlier, the major difference with a Magnum package is the valvetrain. Naturally, Magnum specific rockers are need. The OEM rockers are actually a very good design, suitable for milder street performance applications.
With lifter oiling confirmed, the pushrods need to be hollow, with oil passages at the tips to transfer oil up to the rockers. Since all Magnum engines were equipped with tall-body hydraulic roller lifters, the factory pushrods will be too short to work with the lower flat tappet lifters. Mopar Performance has a pushrod package designed to mate the standard Magnum valvetrain with a hydraulic flat tappet cam. Competition Cams provides pushrods in their retrofit valvetrain kit, PN 1425-KIT, so you are covered there. Any custom pushrod supplier can provide the required length pushrods where modifications require a special length. In fact, once the length is determined, the pushrods can probably be found in most aftermarket cam companies catalog as a stocking part by length listing, since the “ball/ball” end configuration in an “oiling” pushrod is the most common type used in the aftermarket.
With the Magnum's vertical intake mounting pattern, a Magnum-specific intake manifold is required. There are those who have gotten around this problem with custom modifications to change the bolt pattern on the Magnum heads, or revising the intake bosses. There are several good aftermarket choices in Magnum carbureted intakes, making bolt-on manifolds readily available. Mopar Performance has both dual- and single-plane intakes available for the Magnum heads, and Edelbrock has recently introduced their excellent Performer RPM Air Gap for this application. Professional Products has a manifold that has a dual bolt pattern, which fits both Magnum and traditional LA heads. You'll need to get intake manifold gaskets for the Magnum application, to match the revised bolt pattern.
Magnum valve covers are needed to work with the Magnum heads, since the number of attachment bolts are doubled for better sealing. OEM valve covers are a decent choice, but for a little more flash, Mopar Performance carries nice cast aluminum covers. The swap to a Magnum top-end is really a bolt-together deal on an LA engine, which shouldn't be too surprising, since that's the way Mopar essentially did it in the first place.
New for 2012: Racers can now use EQ’s cast iron Magnum cylinder head (Part #CH318B) as a stock replacement for three divisions: Hobby Stock, Northern and Southern SportMod. EQ's Magnum cylinder head replaces a stock 1992–2004 Chrysler 318/360 head and is machined with a pre-1990 LA-style intake pattern that still uses all Magnum rocker parts.
Click the link below to read our Magnum cylinder head articles in Popular Hotrodding magazine.