Dan the man
Well-Known Member
Dollar for dollar which one would be the better choice for simple performance upgrade?
LA / Magnum blocks
- Thread starter Dan the man
- Start date
-
Magnum
Superior pan and valve cover gasket
better factory machining
Hyperuetetic pistons
Metric rings
Lighter rotating mass
Heads as Good as any stock 340
1.6 rocker arms
Factory roller camshaft
More compact, more overall engine compartment room
Dead end bolt toles, not water leaking problems like LA
ETC
How many LA engines have you seen with 100k plus miles that have factory hone marks and almost no cylinder ridge
Comlete motor trans bracket pulleys etc.
$359-600
Superior pan and valve cover gasket
better factory machining
Hyperuetetic pistons
Metric rings
Lighter rotating mass
Heads as Good as any stock 340
1.6 rocker arms
Factory roller camshaft
More compact, more overall engine compartment room
Dead end bolt toles, not water leaking problems like LA
ETC
How many LA engines have you seen with 100k plus miles that have factory hone marks and almost no cylinder ridge
Comlete motor trans bracket pulleys etc.
$359-600
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Dan the man
Well-Known Member
Good enough for me.
Jarlaxle
Well-Known Member
Saw one with 330,000 miles that looked factory fresh. (AHB Diplomat, factory moly rings.)
Projectile Dart
Well-Known Member
I am not disagreeing with anything here but more of a question. You said more "compact". I was under the impression that externally they were basically identical as a package?
Placement of accesories
furrystump
Well-Known Member
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The question was about the block? No? Not rotating assembly, not heads, not accessories. The block, lifter bore machining tends to be less of an issue with oil pressure loss at higher roller lift numbers. Provision for roller lifters. Block material? Who knows?! If you’re starting a build, its getting machined anyway.
No advantage either way, unless you want roller lifters. I don't run roller lifters.
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Superior pan and valve cover gasket - not worth much
better factory machining - debateable
Hyperuetetic pistons - no thank you, I've seen what they do when they fail
Metric rings - No much if any
Lighter rotating mass - Really? How much?
Heads as Good as any stock 340 - Not true
1.6 rocker arms
Factory roller camshaft
More compact, more overall engine compartment room - Not buying that one
Dead end bolt toles, not water leaking problems like LA - My early LA's have blind head bolts, never had any water leaks from threaded holes in the block
ETC
How many LA engines have you seen with 100k plus miles that have factory hone marks and almost no cylinder ridge Quite a few actually, used to get well maintained engines, lightly hone with torque plates and reuse the pistons on budget builds.
Either one if your rebuilding, there is difference in the short block, not enough to consider it an entirely different engine. Later LA or magnum if you want factory hydraulic roller. LA allows more head option unless I you drill the magnum block or rockers that work with oiling through push rods. Magnum heads work really well with a basic 4bbl cam and headers but if rebuilding your probably gonna need to replace the heads so not much advantage once going that route.
MopaR&D
Nerd Member
I vote Magnum for all the same reasons @Brooks James noted. I pulled a complete short block from a local junkyard for $150, couldn't find the mileage since it was a 2000 Dodge truck with the digital odometer and the wiring harness was hacked out. Based on the condition of the truck it was likely around 200k miles.
Bores still had crosshatch, all I did was install new rod bearings and 'sent it' with ported Edelbrocks, port-matched RPM intake and custom-ground hyd roller cam. Still running strong and tight after 6000 miles or so (including some track days and lots of fooling around) in my '70 Duster.
They do have better factory machining, I haven't confirmed that myself with measurements but I'd bet the decks are much straighter and the tolerances are much tighter than back in the 60s-70s. The casting quality of the block was visually much better than the handful of LA blocks I've inspected. I did check how far the pistons were down at TDC and they were all right at .050". LAs usually have more variation between cylinders. Pistons are also tighter-fitting in the bores than factory LAs.
The pistons may be hyper but I've never heard of one failing in a factory Magnum engine and they were installed in 1-ton pickups pulling 10k+ lbs and often had detonation issues due to the intake plenum gasket going bad and sucking in oil from the valley...
I don't know exactly how much lighter the rotating assembly is but it's enough to require offset balance weights on the damper and flywheel/flex plate about half of what a 360 LA requires.
Magnums keep the cylinder crosshatch even if they aren't maintained well and they keep it to 200k+ miles thanks to EFI. LAs won't do that.
I'd also say it's more of a wash regarding heads, J/X heads with 2.02 valves will have more peak flow but Magnums have more velocity and low-lift flow. But they're also "weaker" and prone to cracks between valve seats.
The rest I agree on. Externally the same as an LA, SBMs never had through-holes for the head bolts, and those better gaskets can be used on either LA or Magnum engines. LA valve covers work on Magnum heads btw I've done it.
Bores still had crosshatch, all I did was install new rod bearings and 'sent it' with ported Edelbrocks, port-matched RPM intake and custom-ground hyd roller cam. Still running strong and tight after 6000 miles or so (including some track days and lots of fooling around) in my '70 Duster.
They do have better factory machining, I haven't confirmed that myself with measurements but I'd bet the decks are much straighter and the tolerances are much tighter than back in the 60s-70s. The casting quality of the block was visually much better than the handful of LA blocks I've inspected. I did check how far the pistons were down at TDC and they were all right at .050". LAs usually have more variation between cylinders. Pistons are also tighter-fitting in the bores than factory LAs.
The pistons may be hyper but I've never heard of one failing in a factory Magnum engine and they were installed in 1-ton pickups pulling 10k+ lbs and often had detonation issues due to the intake plenum gasket going bad and sucking in oil from the valley...
I don't know exactly how much lighter the rotating assembly is but it's enough to require offset balance weights on the damper and flywheel/flex plate about half of what a 360 LA requires.
Magnums keep the cylinder crosshatch even if they aren't maintained well and they keep it to 200k+ miles thanks to EFI. LAs won't do that.
I'd also say it's more of a wash regarding heads, J/X heads with 2.02 valves will have more peak flow but Magnums have more velocity and low-lift flow. But they're also "weaker" and prone to cracks between valve seats.
The rest I agree on. Externally the same as an LA, SBMs never had through-holes for the head bolts, and those better gaskets can be used on either LA or Magnum engines. LA valve covers work on Magnum heads btw I've done it.
Professor Fate
Push the button, Max...
Lotsa variables here, so it will depend on your goals, and your definition of "simple performance upgrade". You need to take into account the whole engine and not just the block in order to make a choice.
Are you looking to conceivably get a block that you may not have to bore, to just do a scuff and re-ring job? Then Magnum or roller LA.
Four barrel and manifold? LA- huge variety of intakes, tons of used ones out there. Magnum- only two choices- Air Gap and clones (okay, there's the Indy ModMan, too. But $$ and not that great).
Heads? LA- lots of good factory heads and tons of aftermarket. Magnum- prone to cracking. Plan on getting replacements, although there's a few starting to show up in the boneyards that already have replacement heads.
Cams? (Ignoring current availability issues) LA- run whatever you want. Hyd., solid, roller... '88ish- '91/'92 came from the factory with rollers. Magnum- most off the shelf magnum cams tend to be RV grinds, since they were originally truck motors. But the selection is getting better in recent years. "Short nose" cams, no provision for driving a mechanical fuel pump.
If you want to know the truth, there is fundamentally no difference between the late LAs and the early Magnum blocks. Late LAs had factory roller cam provisions identical to the Magnums. The early Magnums were still drilled for rocker oiling, it just wasn't used (after a couple years they stopped drilling that passage in the block) so you can still use LA heads on the early Magnums. The Magnums had the truck mounts cast in the sides in addition to the LA mounting ears. The LA 273/318/340 had identical oil pan end seal diameters, LA 360 and magnums had "big and littles". Otherwise VERY little difference in the blocks themselves. Your chance of finding a good block are better with the Magnum simply because they're newer, and the FI does a better job preserving the bores. The LAs are older and may have multiple rebuilds under their belt already...
Your choice will depend on your intentions.
Are you looking to conceivably get a block that you may not have to bore, to just do a scuff and re-ring job? Then Magnum or roller LA.
Four barrel and manifold? LA- huge variety of intakes, tons of used ones out there. Magnum- only two choices- Air Gap and clones (okay, there's the Indy ModMan, too. But $$ and not that great).
Heads? LA- lots of good factory heads and tons of aftermarket. Magnum- prone to cracking. Plan on getting replacements, although there's a few starting to show up in the boneyards that already have replacement heads.
Cams? (Ignoring current availability issues) LA- run whatever you want. Hyd., solid, roller... '88ish- '91/'92 came from the factory with rollers. Magnum- most off the shelf magnum cams tend to be RV grinds, since they were originally truck motors. But the selection is getting better in recent years. "Short nose" cams, no provision for driving a mechanical fuel pump.
If you want to know the truth, there is fundamentally no difference between the late LAs and the early Magnum blocks. Late LAs had factory roller cam provisions identical to the Magnums. The early Magnums were still drilled for rocker oiling, it just wasn't used (after a couple years they stopped drilling that passage in the block) so you can still use LA heads on the early Magnums. The Magnums had the truck mounts cast in the sides in addition to the LA mounting ears. The LA 273/318/340 had identical oil pan end seal diameters, LA 360 and magnums had "big and littles". Otherwise VERY little difference in the blocks themselves. Your chance of finding a good block are better with the Magnum simply because they're newer, and the FI does a better job preserving the bores. The LAs are older and may have multiple rebuilds under their belt already...
Your choice will depend on your intentions.
MopaR&D
Nerd Member
You can also use hollow pushrods and aftermarket rockers to get oil to the valvetrain if you use LA heads on a later undrilled Magnum block. Or do it the hard way like I did and make an external oiling setup lol.
'68cuda416
Well-Known Member
Not for most of the guys on here.....330k magnum engines same wear as when they were factory fresh....all I will say is it's no surprise the problems some have on here and the lousy running cars some have.
Fuxk! 2nd time replying. Freakin phone blinked and I lost everything. Ugh!
There are some advantages you listed that are NOT!
Superior pan and valve cover gasket
I do like the oil pan gasket but the valve cover gasket, no advantage. I’ve NEVER had any problems with LA valve cover gaskets.
better factory machining
Marginal and debatable
Hyperuetetic pistons
Not always a plus but I like them. Just because there a hyper slug doesn’t afford any meaningful advantage
Metric rings
Zero at the bolt on go fast parts and a cam
Lighter rotating mass
Same as above
Heads as Good as any stock 340
Show me the numbers! The heads are good for what they are.
1.6 rocker arms
There only advantage is when you use them on a cam designed for a 1.5 or lower rocker ratio for the increased rate of lift and overall lift
Factory roller camshaft
The factory cam is a broom stick falling on its face at 4500. The only advantage is you can reuse the roller lifters on the new cam. So, the price of the new roller cam vs the new price of a LA cam & lifters is….
More compact, more overall engine compartment room
I don’t see this as an advantage at all since LA V8’s were in, IIRC, every car Chrysler produced. The P/S pump gets into the battery space requiring the search and obtaining a van P/S bracket. This is not always so easy for everyone across the country.
Dead end bolt toles, not water leaking problems like LA
ETC
I don’t know what etc. implies, but if the factory LA heads end studs are in good shape, they should not leak water ever. If they do, there not in good shape. A small caveat.
How many LA engines have you seen with 100k plus miles that have factory hone marks and almost no cylinder ridge
Zero Credit the FI & computer system for that.
Comlete motor trans bracket pulleys etc.
$359-600
Not where I was from! 5.9’s start @ 1K which do not include the accessories or there brackets on the engine or computer. Just the water pump.
Magnum he says. I’m taking up the otherwise point of view ….
There are some advantages you listed that are NOT!
Superior pan and valve cover gasket
I do like the oil pan gasket but the valve cover gasket, no advantage. I’ve NEVER had any problems with LA valve cover gaskets.
better factory machining
Marginal and debatable
Hyperuetetic pistons
Not always a plus but I like them. Just because there a hyper slug doesn’t afford any meaningful advantage
Metric rings
Zero at the bolt on go fast parts and a cam
Lighter rotating mass
Same as above
Heads as Good as any stock 340
Show me the numbers! The heads are good for what they are.
1.6 rocker arms
There only advantage is when you use them on a cam designed for a 1.5 or lower rocker ratio for the increased rate of lift and overall lift
Factory roller camshaft
The factory cam is a broom stick falling on its face at 4500. The only advantage is you can reuse the roller lifters on the new cam. So, the price of the new roller cam vs the new price of a LA cam & lifters is….
More compact, more overall engine compartment room
I don’t see this as an advantage at all since LA V8’s were in, IIRC, every car Chrysler produced. The P/S pump gets into the battery space requiring the search and obtaining a van P/S bracket. This is not always so easy for everyone across the country.
Dead end bolt toles, not water leaking problems like LA
ETC
I don’t know what etc. implies, but if the factory LA heads end studs are in good shape, they should not leak water ever. If they do, there not in good shape. A small caveat.
How many LA engines have you seen with 100k plus miles that have factory hone marks and almost no cylinder ridge
Zero Credit the FI & computer system for that.
Comlete motor trans bracket pulleys etc.
$359-600
Not where I was from! 5.9’s start @ 1K which do not include the accessories or there brackets on the engine or computer. Just the water pump.
Any real advantage would be thicker cylinder walls, decks, or stronger web or caps. I don't know of any of these advantages to either, except if the early 318 is true. They are all high nickel castings and a good place to start. I have little experience with anything past 1975. I view them all as the same 273, 318, 340, 360, 5.2, or 5.9. They all have different pluses and minuses, and slightly different characters. Some have better parts, but it matters little with the current price of 360 heads or aftermarket heads. Do you know what do you want? What is available to you?
Professor Fate
Push the button, Max...
Just fishin' for controversy again. Hasn't even been back.
When will I learn...?
When will I learn...?
IMO, it’s an entertaining thread just to split hairs.
Nothing more, nothing less.
Nothing more, nothing less.
I didn't see Magnum moly rings or thermal coated piston skirts listed above.
Plus, if it's a 9.0:1 compression magnum.....it's likely 9.0:1 or very close vs the "not as advertised" ratios I see mentioned all over FxBO about earlier engines.
Plus, if it's a 9.0:1 compression magnum.....it's likely 9.0:1 or very close vs the "not as advertised" ratios I see mentioned all over FxBO about earlier engines.
Not fishing for controvery, I question everything., accept very little at face value.
Just a little info to add. Weights of stock blocks by year. Link at bottom.
Same scale (new) same day
8-28-72 340 4.070 158#
2-19-71 318 4.070 122# was a running dirt track motor
5-7-70 340 4.070 159#
10-17-96360 4.040 175#
6-17-70 360 4.030 165# smallest distance between farthest apart bores
4-26-78 360 4.030 165#
1-2-97 360 4.000 179#
7-19-91 360 4.000 174# Roller has the thick pan rail also
8-30-73 318 3.910 165# Same casting as 122# block
9-19-96 318 3.910 177# Has thick pan rails
1-16-67 273 3.625 166#
Stock SB block info
Same scale (new) same day
8-28-72 340 4.070 158#
2-19-71 318 4.070 122# was a running dirt track motor
5-7-70 340 4.070 159#
10-17-96360 4.040 175#
6-17-70 360 4.030 165# smallest distance between farthest apart bores
4-26-78 360 4.030 165#
1-2-97 360 4.000 179#
7-19-91 360 4.000 174# Roller has the thick pan rail also
8-30-73 318 3.910 165# Same casting as 122# block
9-19-96 318 3.910 177# Has thick pan rails
1-16-67 273 3.625 166#
Stock SB block info
Dan the man
Well-Known Member
What scale did you use. A 122# for a complete running engine??
Dan the man
Well-Known Member
I did not obtain this information. Just regurgitating findings from the Moparts thread linked at the bottom of my post.
It’s my assumption the poster was also surprised by that 122# block.
Dan the man
Well-Known Member
Oh, thanks for passing it on. I don't know why the automotive industry wants to build lighter engines, the little weight that they save with doing so will never be noticed. I would put quality, durability in engines if I was in charge of that department
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