Magnum vs LA block...differences...preferences

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Caco2120

Caco2120

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So as im pondering my future engine choices im left wondering if a magnum or LA based block is my best bet.

I seem to gather that the magnum block carry some "negative" ora..vs an LA...but short of being limited to fewer aftermarket head and intake options...i cant pinpoint any other negatives.

So assuming a sub 500 horse engine...

There are intakes and heads avail in the aftermarket that support 500 horse for both... PLUS a roller cam...on the mag...

So why one vs the other? Educate me on the differences please!

Seems a mag with an la timing cover and roller cam is pretty much a super substitute for a non roller LA?

Lets hear it! Thanks in advance!!
 
without a huge explanation....
  • the magnums have a little lighter rotating assembly, the ring grooves are in a little better location, and all have roller camshafts.
  • LA's do offer some roller blocks (later years)
Both will work, usually easier to find a magnum, (EQ heads or aluminum heads are available), happy hunting
 
It's more a preference.
Both work great.
Different rocker arms, one more easier and possibly cheaper 'given you use factory rollers and spider'


I
 
The only draw back is (IMO) oiling the LA head in a conventional manner. A member here drilled at the rear of the heads and down the ear rockershaft stand to create an alternative. He “T’d” at the oil sender location and ran oil lines to the heads. The attaching bolt was also drilled to allow the oil up and to fill the rocker shaft.

To a lesser degree, the deck height is shorter so when you use LA pistons, depending on the deal, they can be at a positive deck height. A thicker head gasket takes care of that. But you can almost always be stuck with a higher comp ratio that your trying to target.
 
Thanks all for the info! Seems if im content with chevy rockers, and a magnum based head....not a ton of reasons to be married to the "LA"
 
Some of the first year or 2 of the magnum engines had the oiling passage drilled to the heads, don't know when they stopped that.
 
One more thing is the amount of external balance (in the 360 vs 5.9l) difference between the two. Make sure if you choose the 5.9l that you couple it up with the necessary external components for balance.
 
...........And there is no longer a difference between 5.2 (318) and 5.9 (360) pans. The Magnums all use the smaller "half moon" 360 LA type pan
 
Magnum block. LA heads (either use external oiling like I did, or get expensive shaft rockers that allow pushrod oiling). Everything LA will essentially bolt up to a magnum block. Taller lifter bores for hYd roller or if you're going solid roller you have to get the taller race styled lifters.
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Magnum rods are .170 thinner up top. Not a block thing but another Magnum thing...
 
Here you go... This is my 360 Magnum dressed took like an LA !!

dscn5079-jpg.jpg
 
Magnum engines were also made with tighter tolerances and more accurate machining. The factory EFI also pretty much eliminated cylinder bore wear; it's rare to find a Magnum engine to not have cross-hatching left over in the cylinders regardless of the miles. Check out Magnumswaps.com it's pretty commonplace for people to take junkyard Magnum short blocks and just build those up, little to no machining is usually required and with proper heads and thin head gaskets you can get 9.5:1 compression out of them.
 
Is there a guide, or information somewhere on how to drill Magnum blocks for LA oiling? Although I have NO experience with Magnum blocks, I recall hearing about better machining tolerances and less core shift in them and the roller LA blocks vs. the older LA blocks.
 
cpearce said:
Is there a guide, or information somewhere on how to drill Magnum blocks for LA oiling? Although I have NO experience with Magnum blocks, I recall hearing about better machining tolerances and less core shift in them and the roller LA blocks vs. the older LA blocks.
Click to expand...

Pretty sure it's just a straight hole from the top of the deck down to the cam bearing but that's about 5" of cast iron to drill through and it needs to be precise to get it to end up in the right place. You can easily see on an LA block where the passage starts and ends and even the casting "bulge" for it, Magnums retained that just skipped the drilling. A machine shop could probably do it but for mine I just went the external oiling route like shown above.

One of the holes in the sides of most LA cylinder heads (at least my Edelbrocks) for bolting up accessories just happens to line up perfectly with the rocker shaft stands... drill that through, re-tap the threads for NPT and you've got oil. For any realistic power level in a street-strip car I'd personally just get a pair of EQ heads and use the Magnum-style rockers, stock or aftermarket.
 
He also drilled the end attaching bolt in order to get the oil to the shaft.
 
Drilled and tapped into the last pedestal, broke through with 1/16 bit.. then took the bolt and drilled up the center and a cross to fill the rocker shaft.
48397026_10210470612840459_4508213036426723328_n.jpg
48412181_10210470612360447_572507303626932224_n.jpg
 
Oh yea dude, those pictures were a click and save.
 
A Magnum head like that?

This is the first time I have ever seen it done. An iron head would be a big PIA to do, if possible.
 
What year is the LA Roller block from? I'd like to find one. Would that block be a good candidate for a solid roller build?
 
mopardude318 said:
What year is the LA Roller block from? I'd like to find one. Would that block be a good candidate for a solid roller build?
Click to expand...
late 80's to 91 is the LA roller.. they're basically a Mag engine with block provisions for LA head oiling. And yes they should work fine for a solid roller, you'll have to use the taller race style solid roller lifters because the lifter bores are taller.
 
Toluene56 said:
late 80's to 91 is the LA roller.. they're basically a Mag engine with block provisions for LA head oiling. And yes they should work fine for a solid roller, you'll have to use the taller race style solid roller lifters because the lifter bores are taller.
Click to expand...
Can you recommend or comment on who has the taller lifter? Or perhaps spec a height?
Thanks
 
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