Im considering building a 408 for my foot brake bracket car over the winter and I'm curious about strength of block differences between the two, I am currently running a 5.9 magnum and really like the ease of the factory roller cam set up so I'm leaning that way. I have both blocks available so that's not an issue...so magnum vs LA...what say ye? Advantages vs disadvantages I'll be planning for something in the 600hp range

from my limited small block experience......Magnum is the way to go. For 600hp all you need is a decent cam and some ported Edelbrock heads. Magnum is a great platform and the blocks are stronger? than the LA ( i think so)

No personal experiance with 600 hp in a stock block, but have r0ead that is on the edge? Worth investigating, maybe shoot for a very light rotating assembly. I like the rollercam option of the magnum. I used sbc 1.6 rockers, Olds 3/8 to 5/16 studs , Comp guide plates on EQ heads. Then you can run a solid roller.

Limited choice of Magnum intakes is an issue unless you get the heads drilled for LA intakes.

in my opinion 600 hp for sure is solid roller territory, the stock hydraulic roller setup is not usable - no advantage for the Magnum. I think either platform can be used, but honestly i think the Mag 5.9 blocks are available in better condition to start with. Valvetrain oiling has to be considered, but there are solutions to use mag heads on LA or LA heads on a magnum.

Regarding the intakes: there is a Indy 360-3M intake available with mag-style bolt pattern, so this is no deal breaker.

Michael

hummm, interesting input, I appreciate it , am I incorrect to think it would be "easier" to convert a magnum to solid roller? My current combo is a stock 5.9 short block with the exception of KB pistons, Hughes hyd roller .576/.587, 1.6 rockers and straight out of the box Eddy's, car weighs 3080 with me in it, 4.10 geared 8 3/4, leaving at 2000, shifting at 5800. Best 1/8 mile time (only 3 passes so far) is a 7.28@97mph. Need to be running 6.50s next year to run the new 6.50 index class, thanks again for all the input

First off, i went with a magnum core for my deal because there are plenty of cheap core motors out there. If you plan on running a 600 hp stock block for a long time that is worth considering. Since the deck height is so tall i would look for a stroker combo that uses the longest stroke commonly available and the longest reasonably priced h beam rods, all to make a big yet light rotating assembly. The more cubes, could equal lighter pistons and less rpm combined with more torque at lower rpm. I don't know if a 4.25 crank is available but would be great to have 430+ cubes.
I did find a 6.125 long hbeam rod on Molners web site .SBC with 2.00 rod bearing. That would allow another .115 stroke on any 2.123(mopar rod size) crank.

Obviously the magnum block is missing the oil feed for the LA head. That being said, you will be limited in head choices at that point unless you are willing to pushrod oil a LA head (which then limits rocker arm choices).

I think what it comes down to is, see what heads are out there that could fit your goals, and decide if you need a solid roller to get there or not. That will guide you which block to use.

You do have other options also, if you really think the newer blocks are better, the 85'ish to '92 LA blocks are more like a magnum with hydraulic rollers, but still feature the oil feed hole for the heads. I have a '91 block in my turbo car, and it has a factory hydraulic roller setup in it, but LA heads.

My understanding is that the Magnum block lifter bores are taller than the LA and pose less risk to exposing oil band on the lifter with high lift cams. If true, the magnum should be more conducive to a high lift roller with less block prep. I don't see pushrod oiling as a big detriment using LA heads, and the better selection of intakes makes it worth the effort IMO. Unless you want to run old iron rockers, there are multiple oil-through rockers available for the LA heads and anything approaching 600hp should be using a good quality rocker. There are other options to getting around the head oiling issue with LA heads on Magnum blocks as well. Unless I can fall into a good 340 block, I'll be going with a Magnum for my future stroker.

The Indy 360-3m is the best magnum intake out there, that's what I use on my Magnum build, it was heavily ported by Shane Studley, Precision Cylinder Heads. He was not impressed with it out of the box. I'm using Bam Solid rollers and Jesel shaft rockers for the reason you mention....640 lift cam.

THE Earlier magnum blocks were still drilled for rocker shaft oiling. I think up to 95/96 years
I agree I have the indy cylinder head intake for a magnum on my 360. But I had to have the indy intake drilled for the L/A head bolt holes, when I switched to the trick flow heads. I am useing PRW 1.6 billey steel Rocker arms with a comp cams 550 solid lift and push rod oiling.

Really good info here, saving the thread and making notes, this is my first real effort at a serious small block build, always been a big block guy so I'm in new territory here, thanks for all the input, I'm sure I'll have more questions

I have the indy magnum intake on my 360. Then I decided to switch to the new Trickflow heads which take the LA intakes. I decided to get my indy intake drilled for the LA bolt pattern..

I feel the same. Lol I am used to messing with big blocks. This 5.9 magnum thsts in my 96 dakota is my first attempt at a small block. But now I find my self already wanting to stroke it out to a 434
Lol

Yeah, I really like racing A bodies, I've built at least half a dozen big block A bodies using the old school fenderwell headers, I helped my cousin build a Duster with under chassis TTI's and while they look good his car is a maintenance night mare...so...here we have a nice little ease of maintenance small block and so far I really like it, racing this weekend in a 7.00 pro tree index class, trying to move up to the 6.50 class next year

I just did one and the thinnest the block sonic checked was .190 on 1 minor thrust at .030, it is a 1995 block. The head oiling is easy to get around with external lines at the rear if needed. The deck was within .003 of square, and smooth, oil holes for the main feeds were already big, really nice block.

what issues are you running into?

Sorry, just saw this....the issue I have is not necessarily a TTI issue, in fact their headers are a work of art...once installed...to me it's the larger issue of under chassis headers, a big block and an A body...even with a mini starter the headers must be removed to change the starter, to remove the headers the engine must be lifted enough to get the header out...gawd help you if the car still has factory k member, motor mounts and torsion bars. On my cousins car we installed the headers in coordination with the engine install so it wasn't horrible but the first time his car ate a starter we got a life lesson