Exact difference between LA and Magnum smallblocks?

[Mach Manny]

Alright guys i've been trying to find more information about the difference/similarities between the early LA sb and the later Magnums. The reason why is that i've got a 94 Magnum in my Jeep, and i want to know what parts interchange between motors. A lot of the time it isn't clarified.

The only big difference i know of is that the magnum's intake bolts are vertical, whereas the LA's are parallel with the deck.

So what are some significant differences/similarities as far as interchangable parts goes?

thanks.

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73 Dodge Charger 400
94 Jeep ZJ 318
78 Dodge van 360

[kchristopher]

Not much will interchange.

Crank and rods should be the same. Pistons are different (lighter in the Magnum, leading to a different imbalance).

LA camshafts won't fit behind the Magnum timing cover.

LA intakes will swap if you grind the holds to accept a verticle bolt and use spacers.

Distributers are the same size, but I'm not sure if an old one will work with the new EFI.



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68 Cuda, twisties style
http://members.nbci.com/magnumcuda/sprfish.htm
96 Club Cab 4x4, Cummins 5spd

[GTXMONTE]

The blocks are basically the same casting, the big diff is the magnum does not have the oil passage drilled from the deck to the cam, the boss is there but not drilled. The heads everyone knows about, either will work on either motor with the right parts. Same crank, rods, pistons(weights vary). The only cam diff is the length, magnums are all injected so the cam has no room to put the fuel pump eccentric on the end(someone makes an adapter though). Timing covers bolt up the same but the magnum is more shallow and has no fuel pump boss. Distributors are the same but if the motor is using factory injection, you will have to use a late dist to fire the injectors.
Basically everything will bolt up and work with the right combo of parts. I have the magnum front cover and all the drive on my Challenger, the serpentine belt is nice and all the acc are in close and mounted well. Had to use elec fuel pump...no big deal. I recently helped a guy that had a roller pre-magnum motor that wanted to use a magnum cam he had gotten free. It was a carb motor, so I welded an eccentric to his steel timing gear, chucked the cam in the lathe and grooved two cam journals to oil the rocker shafts and he was good to go. As I said, all the parts will interchange, you might just have to be creative.

Monte Smith

[HankL]

If you can find the 3 issues of Hot Rod magazine for Aug Sep Oct 1998, Al Kirchenbaum wrote a very good 20+ page article with many pictures and tables called MAGNUM MANIFESTO on the differences between the Magnum and LA engines including what mods will make different parts work.

You can see the cover of the issue at:

http://www.hotrodarchives.com/TOCFull.asp?toc=199808

[Mach Manny]

Thanks for the info. How about starters, headers [attatchment to the heads], oil pans, transmission bellhousings [aw-4, 727], motor mounts, water pump, dampener, ...

Untilmately, i want to work with Rossi and swap in either a stroked 383 or a stroked magnum 360 into a early Grand Cherokee for maximum torque to spin 35-38" tires. Front/rear axles will be d44/d60 or d60/d70, and custom suspension i'm still trying to design.

I'm still deciding whether to go MPI or carb cuz the new Holley looks pretty tempting. Anyways, the subframe and chasis will be built around the swapped in motor, so naturally new crosmemembers will be stalled, and work with the k-member.

hank - thanks for the tip about the backissue. Too bad i just start subscribing last year.

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73 Dodge Charger 400
94 Jeep ZJ 318
78 Dodge van 360