L.A 360..Magnum ?

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71scamp78

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Ok just bought a 71 Dart it has a running 360 seems to have been apart at some point at least it appears that way..all newer gaskets even head gaskets. Has brass freeze plugs as well but even with all that they could have simply just put all new gaskets on it. It's a 71 360 engine and I'm pulling it out because of all the leaks and and to clean it up, plus I'm gonna have trans gone through as well. Has J heads as well and the way it idles I'd guess a stock cam or close to it. Goal is a street , strip car with 3.55 gears and a stall to match cam and gear combo. I would like to make around 400 hp which should be easy and very streetable. Should I use the LA 360 in car or go with a magnum engine I've always wanted to try..I know the magnums have some better sealing surfaces and roller cams to boot. But aside from that is it worth it. I mean I'm not sure what I'll find when I pull engine..hopefully it's still got bore life left. What combo of heads , cam and pistons should I use. Should I even use the J heads or go aftermarket. Thanks in advance guys.

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Magnums are from ma Mopar the best heavy duty non performance small block Mopar. Find out why they are superior at
Magnumswaps.com
 
LA, cause you have it and it has the better factory heads of the LA bunch.

You can put mag heads on.

The mag is roller..but no shaft mount, short cam snout so need adapter, new balancer for old pulleys, new intake, it's basically gonna cost you more and yield very little if any advantage other than a roller cam..which you will also have to buy new unless you like .405 lift and 0 o lap.
 
LA, cause you have it and it has the better factory heads of the LA bunch.

You can put mag heads on.

The mag is roller..but no shaft mount, short cam snout so need adapter, new balancer for old pulleys, new intake, it's basically gonna cost you more and yield very little if any advantage other than a roller cam..which you will also have to buy new unless you like .405 lift and 0 o lap.

Ok the j heads would have the smaller valves correct. Should I use them and be able to get around 400hp or get a set if eddie, eq or trick flow heads. I'm sure the cast crank is ok and the rods. Price to recondition rods may be just as cheap to get new ones.
 
Ok the j heads would have the smaller valves correct. Should I use them and be able to get around 400hp or get a set if eddie, eq or trick flow heads. I'm sure the cast crank is ok and the rods. Price to recondition rods may be just as cheap to get new ones.
Find out what your local shop charges and decide based on that.
400 from small valve j heads, possible for sure. I'd buy some cheap chevy valves and work those.. but for you that sounds out of your realm, so maybe a set of promax heads would be right up your alley. You won't have to mess with porting or machining them etc. Bolt on.

For me, I can have a short block machined as package with cam bearings, freeze plugs, bored n honed cleaned for 350
...and rods resized and pistons pressed for 120 , crank ground for 90. Head valve grind package is 400.

Pistons like speed pro 9.1 hyper are 155
Bearing off ebay or from the shop rod and main 56 bucks! Gaskets 50, cam kit from scummit 135. 45 dollar oil pump, 56 dollar timing set summit.. springs 70..cheap.
 
Like almost everything else these days, Eagle rods are made in China, but their I beam rods are made to some nice tight specs. They also use a bushed small end for a floating pin, ARP 2000 bolts, and a matched set of 8 weigh within 1 gram of one another. It's a 6000 rpm rod all day long. About $300 and change for a set of 8, and arguably better forgings than OEM. Last set I bought was $319 shipped to my door.

By the time you take the OEMs and
1. Shot pen
2. Magnaflux
3. Check for straightness
4. Install new ARP rod bolts
5. resize the big ends

You will still be into time cycled stock forged rods with typical pressed pins for way more than these new. Add about $150 to that $300 price tag and you can have new Eagle H beam rods which are even better.

Make no mistake, I'm no big fan of China. They do make some junk. However they will make whatever you want, and to the exact specifications you want. Some stuff coming out of there is pretty good.

Look into procomp bare heads. Eddy copies. They are essentially cast as magnum chambers and runners in an LA style aluminum head. The guides are junk, and they are machined for 2 02"-1.60" chevy valves. But install new guides for whatever valves you want to run.
 
A 71 360 block would be an early casting. I seem to recall those were excellent candidates for stroker motor and preferred by some.
I keep a virgin set of J heads just in case I need a replacement for x head. Just add larger valves.
Magnums are great too.
 
KB107s/63cc alloy heads/.028 gasket/ with a 230@.050cam/ 750DP on an AirGap.
Falls together at about 10.7/176psi/.040Q/and altitude adjusted Effective Dcr of ~8.5@500ft.. Mine went 93 in the Eighth with 3.55s. I run dual 3" full-length pipes with NO crossover. The Wallace calculator says 433hp at 3457pounds. Your Dart is lighter, so it will post a higher trapspeed. If you're ok with a lil less power, I highly recommend the old Hughes HE2430AL, or something equivalent. That was a 270/276/110 and 223/230@.050; better on the street, more bottom end, great fuel mileage, and only a lil slower . I set mine up to run 7000/7200 on the backside of the power-curve. Super much fun.
 
KB107s/63cc alloy heads/.028 gasket/ with a 230@.050cam/ 750DP on an AirGap.
Falls together at about 10.7/176psi/.040Q/and altitude adjusted Effective Dcr of ~8.5@500ft.. Mine went 93 in the Eighth with 3.55s. I run dual 3" full-length pipes with NO crossover. The Wallace calculator says 433hp at 3457pounds. Your Dart is lighter, so it will post a higher trapspeed. If you're ok with a lil less power, I highly recommend the old Hughes HE2430AL, or something equivalent. That was a 270/276/110 and 223/230@.050; better on the street, more bottom end, great fuel mileage, and only a lil slower . I set mine up to run 7000/7200 on the backside of the power-curve. Super much fun.

Sounds like a pretty good combo there for sure. I'd be happy running sub 8 sec in the 1/8 mile . Should be easy
 
Odds are the magnum won't even need bored. Low tension rings and efi make em last forever.

And you'll NEVER wipe a cam lobe with that roller cam. To me, the roller cam and its improved profiles makes this a no brainer. The magnum heads are pretty good, and net you 1.6:1 rocker arm ratios.
Electric fuel pumps are something you ought to do anyway.
 
Odds are the magnum won't even need bored. Narrower rings and efi make em last forever.


And you'll NEVER wipe a cam lobe with that roller cam. To me, the roller cam and its improved profiles makes this a no brainer. The magnum heads are pretty good, and net you 1.6:1 rocker arm ratios.
Electric fuel pumps are something you ought to do anyway.
Fixed

Actually 360 EFI engines suffer from extreme lean conditions and that's why they usually crack the heads ...which most Magnum heads have cracks even if they still run.
Cause is phlenum gasket and o2 sense.
See when O2 sensors go bad they go to the lean side usually it's like pretty much always. Then usually get the classic plenum gasket leaking on that barrel intake manifold -vac leak city and sucking oil too..that design also sucks for anything above 4500 RPM. And I'll just toss it in there that you'll probably want to get the heads rocker stands tapped for 3/8 so you can put some real springs in there.
 
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KB107s/63cc alloy heads/.028 gasket/ with a 230@.050cam/ 750DP on an AirGap.
Falls together at about 10.7/176psi/.040Q/and altitude adjusted Effective Dcr of ~8.5@500ft.. Mine went 93 in the Eighth with 3.55s. I run dual 3" full-length pipes with NO crossover. The Wallace calculator says 433hp at 3457pounds. Your Dart is lighter, so it will post a higher trapspeed. If you're ok with a lil less power, I highly recommend the old Hughes HE2430AL, or something equivalent. That was a 270/276/110 and 223/230@.050; better on the street, more bottom end, great fuel mileage, and only a lil slower . I set mine up to run 7000/7200 on the backside of the power-curve. Super much fun.
Can you do everyone here a favor and show us the time slip that you ran 93mph with your 360 in the 1/8th .

We look forward to seeing it.
 
First i EVER heard of this. It's not often an engine will default to a dangerous condition.
You should own a focus sometime.
They spend half of their lives lean and pinging. Yes they fail usually to the lean side and the computer dumps fuel, Rich ,kills catalytic converters and makes more heat from slower burns.
They can fail either way...Truth be told
 
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Both the Magnum and the LA make for good combos. But if you already have a good la then I would definitely go with that it'll also look much more at home in the engine bay with its five valve cover bolts and it's proper angled manifold bolts. I think the condition of your heads will make a big difference in which direction you go if the heads have been rebuilt and are in good shape that would be great if they're shot then you'll have other decisions to make.
 
First i EVER heard of this. It's not often an engine will default to a dangerous condition.

F or whats its worth reading the destructions manual for my -97 dodge ram it clearly states that pinging under light load is normal and not a problem so not nescessarily all that dangerous,sure magnums are known for their heads cracking betwen valves but do you ever hear about that crack ever turning into a real problem?

You should own a focus sometime.
They spend half of their lives lean and pinging. Yes they fail usually to the lean side and the computer dumps fuel, Rich ,kills catalytic converters and makes more heat from slower burns.
They can fail either way...Truth be told

The destructions manual for my -97 dodge ram clearly states that pinging under light load is normal and not a problem,yeah i know Magnums are know for their cracked heads (not to be confused with owned by crackheads) but i dont think i ever heard about those cracks actualy hurting anything.
 
F or whats its worth reading the destructions manual for my -97 dodge ram it clearly states that pinging under light load is normal and not a problem so not nescessarily all that dangerous,sure magnums are known for their heads cracking betwen valves but do you ever hear about that crack ever turning into a real problem?



The destructions manual for my -97 dodge ram clearly states that pinging under light load is normal and not a problem,yeah i know Magnums are know for their cracked heads (not to be confused with owned by crackheads) but i dont think i ever heard about those cracks actualy hurting anything.
A later tech bulletin said to go one step colder on the spark plugs
 
my 2 cents, build a magnum, store the running 360....just incase a problem with the magnum develops.
 
my 2 cents, build a magnum, store the running 360....just incase a problem with the magnum develops.
The la. 360 has a little noise..something up high not a rod or main noise..seems it would be easy to pull a low mileage magnum out of a truck and just stuck a cam, intake , carb and headers on it and have some fun..may sell the 71 360 engine. Not sure what it's worth really..
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The la. 360 has a little noise..something up high not a rod or main noise..seems it would be easy to pull a low mileage magnum out of a truck and just stuck a cam, intake , carb and headers on it and have some fun..may sell the 71 360 engine. Not sure what it's worth really..View attachment 1715760501
More than usual the 70-71 block have thicker cylinder wall I have heard of
100 thousandths ovebore, safely
 
More than usual the 70-71 block have thicker cylinder wall I have heard of
100 thousandths ovebore, safely

Yeah but one might also want to consider coreshift and what rust may have done to the waterjackets over the course of the last 50 years..
 
Can you do everyone here a favor and show us the time slip that you ran 93mph with your 360 in the 1/8th .

We look forward to seeing it.

That was 2004, com'on, it wasn't that big a deal to me.
If I'd have known I was someday gonna be called out on it on a Forum I hadn't yet even heard of, I mighta kept track of it's whereabouts. The only reason I was there, was because a buddy kept bugging me to run against his "oh-so-hot tunnel-rammed-340."
We both have same cars; his was 340/A833/4.30s to my 367/Commando-833/GVod/3.55s. The 4.30s were mine that I loaned to him, lol, on a spool. The buddy thought his hot 340 could take me. I said lets go to the track.
It wasn't even close.
My secret weapon is gear splitting; Mathematically, I was expecting to trap at hi 80s at high 5000s; (230Hughes cam). But that lil 367 hit 7000 out of the gate and stayed there all the way to the traps; I'm not kidding; the tach was "stuck" on 7000, I rode it like that from out of the 60 ft, to the trap, guessing when to shift. I really thought the clutch was smoked, but kept my foot in it, when she stayed off the rev-limiter (7200).
First/first-over/Second/ and second-over, trapping, one track official said, still hazing the 325/50-15 BFG DRs (yeah it was a shitty track). Another track official wandered over to my parking spot and recommended I drop my tire pressure. OK I said, not telling him that the pressure he had just recommended was already in there, lol.
This was an old airport runway, so no scales. I had scaled the car, the day before on a nearby truck scale at 3457 pounds.
ET was 7.92 with a 2.2plus 60ft.
My buddy don't bug me no more, lol. But we're still good friends. And yes I got my 4.30s back about a week later, which I later sold to a different friend.

BTW;
The gear splits on that combo are .78-.80-.78, which, shifting at 7000 should be an rpm drop of 1470rpm. We both know that a 7000 shift rpm is way too high for this combo. I drove it like I drive it on the street.
The 230* cam probably peaks closer to 5200/5400. So a better shift rpm mightabin 5600/5700 . and then, the rpm drop woulddabin 1200 or less. But like I said, it was a one-run deal, to shut my buddy up; and all the DAs who ever told me that I shouldda built a 340 cuz you know, everybody just knows that the 340 is King of the hill..... . Had the car not run this number, I mighta made a few more runs that day, but I was good with what it did.
Yeah, I was surprised too. I even went immediately back to the booth and inquired as to the veracity of his equipment; but he said no one else was complaining. I even went to talk to the guy in the other lane who I ran against (TnT), but no He said, his time looked right on, and his speed was faster. So I did my due-diligence.
Well there ya go;
hot street 340s @3450, don't usually get out of the 80s, do they. My buddy's car is a lil lighter than mine, and altho I don't remember his trapspeed, I think it was in the range of 84 to 87, still pretty hot, given that crappy track.
Please notice that nowhere in this post did I diss the tail-light-sucking 340, lol........
Oh yeah I shouldda mentioned, my buddy runs the Mopar 292/292/108 cam, as compared to my Hughes 276/286/110; as if that makes a difference, lol.. And he runs the 2.66-1.92-1.40-1.00 box compared to my 3.09-2.41-1.92-1.50/ 1.40-1.09-1.00-.78od GVod in red. Both are 68 Barracudas.

Even if I hadda kept that lil scrap of paper, the ink on it 17 years later, would have long ago faded into oblivion. Like I said; to me it was no big deal, I was just there to quiet the 340 worshipers.
 
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F or whats its worth reading the destructions manual for my -97 dodge ram it clearly states that pinging under light load is normal and not a problem so not nescessarily all that dangerous,sure magnums are known for their heads cracking betwen valves but do you ever hear about that crack ever turning into a real problem?



The destructions manual for my -97 dodge ram clearly states that pinging under light load is normal and not a problem,yeah i know Magnums are know for their cracked heads (not to be confused with owned by crackheads) but i dont think i ever heard about those cracks actualy hurting anything.
This is true.
They can run for thousands upon thousands of miles and never hit water...but the issue becomes a burnt seat when the crack is a break in valve seal , combustion shoves through.
I've changed the phlenum gskt 3 times in 10 yrs! Crap design!lol check this out though, it a a redesign in the gasket 3 times
Victor reinz-one small section wider
Doorman-wider all the way around
Felpro-as factory

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