Installing a Magnum in place of an LA is mostly a direct swap, but there are a couple of areas where the Magnum differs significantly enough from the LA that modification is required.
Grind for Headers
Be sure to check your headers for fitment before installing the engine in your car. Depending on which headers you use, you may have a significant grinding job to do. Some headers will hit the truck style engine mount on the driver’s side. We had to remove nearly the entire mid-mount on our engine. This grinding may be possible with the engine in the car, but it would be difficult, messy, and unpleasant. An angle grinder makes quick work of this, but is messy! Make sure the engine is properly sealed during grinding, and take the correct precautions to protect yourself and your car from the flying iron dust!
The standard Hooker Comp headers(and the Dynomax, Blackjack, Pacesetter, and Summit copies) require grinding to fit. In most cases, Doug’s, Hooker Super Comp and TTi do not.
Unless you’re using the stock Magnum EFI or another crank trigger style ignition system, the stock Magnum distributor is not going to work for your swap. Fortunately, the LA style distributor is a direct drop in. We recommend a unit with a performance advance curve built-in.
We recommend using a mini starter. Even with the smaller starter, the block may still require some minor grinding for fit. If possible, test fit the starter before installation to see if grinding is required. While you can do this with the engine in the car, but it is much easier when the block is on the engine stand.
Mopar Small Block engines are hard on timing chains because of the unusually long distance between the cam and crank centerlines. The timing chains stretch easily, resulting in poor performance, or worse, breakage. The classic symptom is the rapidly fluctuating mark on the balancer when using a timing light. The stock timing chain on a Magnum is not a performance piece. A We recommend the best double roller timing chain you can afford. We also highly recommend the use of a Mopar Timing Chain Tensioner.
To install a Magnum motor in your car, you will need a car-style mid sump oil pan and matching pickup tube. All Magnum motors have rear sump truck-style oil pans. If you’re putting the Magnum in a truck or SUV, the existing pan will work.
The Chrysler LA 360 oil pan will bolt-up to the Magnum with no modifications, but you aren’t stuck with the typical leaky four-piece 360 Gasket. The Magnum uses a one-piece oil pan gasket. If you use the Magnum timing cover, you can use the gasket as-is. It is possible to use the Magnum gasket with the LA timing cover, but modifications to the front of the gasket are required. Details here: Oil Pan Gasket