Magnum 318 -

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Magnum 318


Old 06-14-2011, 11:04 AM
markdawson38 is offline
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Default Magnum 318

What is the difference between a Magnum 318 and a regular 318? Also, are the parts interchangeable?? Will my intake work from my 1997 Dodge Ram 1500 4X4......

How do you know it is a magnum?
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Old 06-14-2011, 01:02 PM
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Two different styles of engine. I think in 92, or 93, the changed to the magnum style. (earlier engines were "LA", whatever that means....) I think ALL 318's after the target date were magnums though. If both engines are indeed magnums, then all of the parts should interchange. If one is an LA though, there are quite a few differences, and a fair few parts will NOT.
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Old 06-14-2011, 01:51 PM
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the magnums use roller lifters and pedistal mount rocker arms, the older 318s used flat tappet hydraulic lifters and a long rocker shaft that all the rockers pivoted on, Magnum cylinder heads are different(closed chamber and better flowing) the intake manifold mounts with vertical bolts as opposed to diagonal bolts of the older engines, you can use magnum heads on the older engine which would allow you to use the magnum intake manifold,

what are you trying to put the manifold from your 1997 on?
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Old 06-14-2011, 02:06 PM
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The LA 318's used roller rockers in the late 80's also.
I believe they started using them in 1987 in cars and 1988 in trucks.
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Old 06-14-2011, 02:12 PM
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The LA designation stands for "Light A" engine. The A engines were the 318's, 360's and I believe 340's from the early Mopar days. The 340 was discontinued by 1970, and I can't recall if any were ever built as an LA option.

The light designation is a reduction in weight by thinning the block castings. I think they saved something like 53lbs off the engine block by casting thinner. This lead to obvious weight savings, reduced raw material manufacturing costs, better heat dissipation and greater fuel economy, at the expense of reducing the number of times the block could be safely machined and the bore enlarged.

A magnum engine is a re-engineered LA block with Magnum heads. Better intake port flow, combustion chamber design, as well as pedestal mount rockers with a 1.6 ratio and more secure valve covers are the big differences between the LA and Magnum heads. Magnum heads can be drilled to bolt on to certain LA engines for a nice performance gain.

The engines were sightly changed with direct-oil thru pushrods, a vertical mounted intake manifold, hydraulic roller lifters and camshaft, electric fuel pump instead of camshaft driven, multi-port computer controlled fuel injection, and a few other goodies I can't recall right now. Some of the very late LA blocks may have been hydraulic roller, I don't know when the exact switch was. All LA's were either carbed, or very late models were TB injection engines.
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Old 06-14-2011, 07:48 PM
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I got inquisitive and had to go looking, here's what I found-

•1985 - Federal 318s went to a roller cam and lifters unless they had the four-barrel
carburetor. I assume this was cars only.
•1986 - 318 receives high swirl heads
•1987 - 3.9 is developed from 360
•1988 - 318 get hydraulic roller cam; 3.9 and 318 get throttle-body fuel injection. Trucks
•1989 - 360 gets hydraulic roller cam
Also the 340 was an LA engine.

Last edited by charlie1935; 06-14-2011 at 07:52 PM.
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