Magnum Vs LA 360

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wes beem

wes beem

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Howdy, Ive always run magnum motors in my builds but i recently came into a D150 with a 1979 360 LA motor.

What difference in power/economy should i expect assuming i removed all of the Smog accessories from the motor?

What i'm really getting at is, Should i still try to find a magnum to replace the LA or wil lthe LA perform the same with the Smog accessories removed?

The general consensus regarding the Magnum seems to be that once you throw headers, a good 4bbl intake and carburetor you can expect to be around 300-320 HP.

Is the same true of the LA? Or does the LA have internal things like Pistons ext that hamstring its power.
 
Hey Wes. Having both scenarios played out in my own cars, both in the same car, I’ll fall you what the LA lacks and you can take it from there. In my experience….

The LA lacks compression. Being a ‘79, in the heart of the crap power years due to emissions, it will only recover so much. This is what I did to my ‘79-360 in my ‘79 Dodge Magnum.

For starters, the car was loaded except a moon roof, buckets, power everything. A 904/8-1/4 w/2.76 gears & 245/60/15’s.
Best mileage was 20 Hwy.

I used a OEM 4bbl intake, Carter 600 AFB, ‘72 trap door air cleaner & K&N filter. A junk yard distributor fired by a Chrysler chrome box, 2-1/4 H pipes dual exhaust off of the stock manifolds. Due to the era I had the car, NY state was doing yearly inspections that included looking for a catalytic converter. I used two high flow units from summit. The car passed for a newer FI engine. I thought it was a reasonable performer.

No cam change, the oem 2bbl cam stayed in. No headers.

The 5.9 Magnum is a ‘03. The long block is stock. I added a Edelbrock 750 Carter AFB, RPM intake, Hooker super comp headers @ 1-3/4, 2-1/2 true dual exhaust into Dynomax super turbos.
A 727/9-1/4 w/3.55 gears on the same tire as above, 245/60/15.

This is a nice performer for what it is. Power to 4500 where it starts to roll over. It’ll keep rpm-ing, but you can tell it’s done.
No accurate Hwy mileage reports. But I think I’m getting 17.

The LA is missing a camshaft & it’s compression was measured to 7.8-1, a bit far from the Magnums 9.0-1.

To beef the LA up, go with a cam and closed chambered heads. Maybe even a light milling on them. IMO, a cam duration greater than 218@050 could use a converter.
 
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Here's some basic mods to a stock LA and Magnum short blocks





In stock form the magnum makes more stock hp and seems to respond a bit better to basic cam 4bbl headers but were only talking like 20 hp or so. Is that worth a swap? It's a bit from CR but mainly do to heads, LA will accept magnum heads but also a little work to the LA heads will also work or better yet a set of speedmasters etc.. if more than basic hot rodding will do.

If the 360 is a good runner I'd stick with that.
 
If you REALLY want hydraulic rollers, I think it'd be worth while.
 
Jomar??? Jolmar??? Makes stud girdles for the Magnum, IIRC, I don’t know if they’re still made though. Would be good if they did.
 
If the LA 360 is in good shape it's probably not worth swapping to a Magnum. I've tossed around the idea of swapping a 5.9L Magnum in place of the LA 360 in my '72 D200 but I'll only go through the trouble if it retains the factory EFI and I get an overdrive transmission with it.

Magnum is overall better when talking close-to-stock setup. More compression, lighter rotating assembly, more precise machining with tighter tolerances, moderately better heads, ROLLER cam. People bring up the rocker arm design which isn't as good as the older shaft-mount design but that makes no realistic difference under about 6,000 RPM. The pedestal-mount rockers are known to be reliable up to the ~6,400 RPM limit of the factory hydraulic roller valvetrain. Ain't no press-in stud mounted Chevy BS.
 
You found a decent 79 D150? With a 360 to boot? My envy is boiling over. I had a 79 with a teener and it was my favorite of all the pickups I had. Just love that body style over the boxy later models.

I also had a 89 D250 with a 360 roller engine with a holley tbi(stock that year). It got up plenty for the big *** truck it was. It had a 9 1/4 rear axle and was a bouncy ride compared to the 79 D150.

So I would stick with the LA. I’m just not enthralled with the magnum. Cracky heads and I like my rocker shafts and the way they are oiled. They did a partial redesign for that magnum engine, but they should have went with a total redesign. They didn’t go far enough.
 
Oh, @wes beem , sorry, what transmission and gear ratio are you working with?
Headers or not?
 
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wes beem said:
Howdy, Ive always run magnum motors in my builds but i recently came into a D150 with a 1979 360 LA motor.

What difference in power/economy should i expect assuming i removed all of the Smog accessories from the motor?

What i'm really getting at is, Should i still try to find a magnum to replace the LA or wil lthe LA perform the same with the Smog accessories removed?

The general consensus regarding the Magnum seems to be that once you throw headers, a good 4bbl intake and carburetor you can expect to be around 300-320 HP.

Is the same true of the LA? Or does the LA have internal things like Pistons ext that hamstring its power.
Click to expand...
  • To me, the biggest advantage for the Magnum is roller cam for todays oils. Yes, for performance magnums have better compression, thinner rings and better heads from the factory.
  • As for the LA advantages, you get a much wider variety of intake choices and the rocker shaft is usually preferred as to the pedestals.
You can do lots to crossover these parts - like put magnum heads on the LA, or put the LA front on the magnum, and such
 
Gear ratio and tire size will point towards a camshaft size area.
Then the performance your after, weight of the vehicle and possible converter change for more stall, camshaft dependent.
 
I've been working on my 79 d200. I decided to go with the magnum. the roller cam,lighter rotating assembly,better rings and less cylinder wear all were selling points. Unfortunately I've torn apart three of them and they all had cracked cylinder heads. So much of the money saved elsewhere had to be spent on cylinder heads.
 
I’ve been running cracked cylinder heads for a long time now. Since according to everyone, they’re all cracked. I just took an otherwise good running engine out of my daughters wrecked ‘03 Durango, slammed it in the ‘79 Magnum, coupled up a 727 and away I went.

It is a little bit of a bummer that there is one iron head and one aluminum head to replace the OEM. At least the Edelbrock is a decent performer with good porting to it available.
 
rumblefish360 said:
I’ve been running cracked cylinder heads for a long time now. Since according to everyone, they’re all cracked. I just took an otherwise good running engine out of my daughters wrecked ‘03 Durango, slammed it in the ‘79 Magnum, coupled up a 727 and away I went.

It is a little bit of a bummer that there is one iron head and one aluminum head to replace the OEM. At least the Edelbrock is a decent performer with good porting to it available.
Click to expand...
I planned on doing the valves and calling it good but i also found junk guides and just couldn't see spending cash on these heads. All of the magnums i pulled apart were really high mileage though.
 
I have a 1994 360 magnum with 80,000 miles with computer. I was going to put it in a 67 fastback but sold the car. It ran great when pulled. Does anyone know what it is worth?
 
Nothing. You're too far away from me for it to do me any good.... haha
 
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everything is there including exhaust manifolds. I also have a 76 la 360 that turns over but needs rebuild. I have a set of J heads that I bought to use on the la.
 
I don't have anything that needs an engine right now but I have 2 360 magnum short blocks in the garage, one is a fresh rebuild that got spoiled by sticky valves on a set of "ready to run" (that weren't) out of the box eq heads where I had valves stick and kiss pistons.... 1st time I ever bought a set of brand new heads// and it bit me in the azz by doing so.
Add that the break in oil came out a silvery slurry mess that I've never had before on a first oil change (2-3 hours of total run time on that one)
This engine was freshly bored 30 over at the time. Total of 6 miles on it when it had to come back out...
I ended up putting a used, sourced from CL, engine in that one. And sent those brand new eq heads to the machine shop for another couple of hundred $$$$ worth of machine work to make them really " ready to run"....

Anyway my son had built a 76 360 that wasn't enough for him so he redid it as a 408 shortly later. (Like 5000 miles)
Since I need at least rings and bearings for the one with the defective heads anyway, I was wanting to buy the rings for the pistons that came out of his LA (same 30 over as my doomed rebuild) and use those.
These are speed pro hyper and coated flat tops with 4 valve reliefs (HP405 or something like that)
I've never been interested in a 7k rpm screamer, anyway. Most of my stuff never sees 4k....
I'm gonna need another set of heads to be able to use this short block when it does get used anyway. They WON'T be EQs. That set that I had trouble with, I picked up directly out of EQ's warehouse, off of the back of their dock in Chicago.

Anyway after all that, would I be able to use pistons meant for an LA in a magnum block? I know the bore diameter is and the stroke, identical between the 2
 
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And before someone asks, in that rebuild that went bad on me, I reused the original factory cam in that engine with new stock replacement roller lifters
 
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