318 la or 318 magnum

M Body General Discussion

  1. kingoftooland

    kingoftooland Active Member

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    well the beast still runs but is WAY tired valve guide seals are shot burns oil and the rear main is pissing oil as I drive when taxes come in I am gona build a motor for my 84 5th ave yea some people say go all out swap a 440 bb nope or even a 360 but for what I do with the car a 318 is just fine but trying to decide if I should stick with a la or get a magnum since the magnum family is more easily available all I am really gona do is get a master rebuild kit from summit and maybe a mild cam n a set of headders I am planning to get this car ready to take to the mopar nationals
     
  2. Duke5A

    Duke5A Well-Known Member

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    You should only entertain Mag motors. Factory 5.2 Mag was rated for 70 more horse power than the 318 LA. Honestly, do not rule out a 5.9 Magnum. If it were me I'd run a 5.9 Magnum rebuilt to factory specs and reuse your exhaust manifolds with a custom dual 2.25" exhaust. Not too loud with gobs of low end torque. Remember, the more torque you have down low the easier it is to get these barges to move with numerically low gears. A 2.94 gear will still be tolerable on the street thanks to the torque and won't wind the motor out on the express way.
     
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  3. kingoftooland

    kingoftooland Active Member

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    hmm because it's got a freshly rebuilt 904 and still has the factory 7 1/4 rear
     
  4. Duke5A

    Duke5A Well-Known Member

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    That 998 will be just fine. The 7.25 is on borrowed time even with a warmed over 318. It's going to have to be upgraded anyhow. Don't hold out on its accord.

    Check Parts Galore. I just saw an AHB 8.25 rear in there last year. They still turn up.
     
  5. kingoftooland

    kingoftooland Active Member

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    ill take a look on sunday I am goin down to the 8 mile n hoover location atm they have 2 5th ave's n a dippy I belive
     
  6. AJ/FormS

    AJ/FormS Well-Known Member

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    The Magnums have four main advantages over the LAs
    1) A higher factory rated Compression ratio; 9.2/9.4Magnum over 8.0 to the LA
    2) A cam rated nearly two sizes bigger that according to my data was installed at 119* , which IMO, is ridiculous if true.
    3) A roller cam
    4) the Magnum heads are said to be, OOTB, better than any other factory SBM heads.

    And the Magnums, if fuel-injected have one drawback; namely either converting the car to run EFI, or converting the engine to run non-EFI.

    If you are rebuilding an engine, for just commuting, as you say; then NONE of this matters. You just buy the appropriate pistons and cam for your combo, and even out the playing field.
    To me, the roller cam is no advantage at all; but some people like the peace of mind that the roller lifters have a reputation of lasting nearly forever, no matter how crappy the oil gets.

    But if you just want a salvage-yard take-out and drop-in , then you will get more bang for your buck, with a Magnum...... unless you have to spend money in the conversion.

    And if you are already at the salvage yard, then for me, getting a 360Magnum is a no-brainer.You can retune that 360 to get better fuel-economy than any stock 318 ever made, and in the meantime, it makes a ton more torque to pull that stinking tall hiway gear back there, and you will finally have some passing power. But this is not a straight RnR.
    But in the above case, if you pick a 5.2Magnum,leave the Magnum cam in it, but retime it to where it belongs, namely 106, that will make a killer bottom end to pull those ridiculously high,hiway gears.

    If you put a performance cam in a 318LA without bringing the compression up
    AND if you do not replace the rear gears at the same time,
    OR install a hi-stall TC ,at the same time,
    then you will be in for a world of disappointment.
    I guarantee you the car will be slower out of the gate, slower from 30 mph, and slower from zero to 60 mph; so don't do it.
    The LA already has a poor 8.0 rated compression ratio, which the 240* factory cam nicely works together with. But with say a 262 cam for instance, the cylinder pressure will drop waaaay into the basement (slanty territory), making an already poor situation, unbearably poor, from which , with 2.45 rear gears or less, it will never recover from, because the power peak of a 262 cam, namely ~5000 will be 57mph even with that 2.74 low gear. Don't do it!

    Headers are still far superior to the factory log manifolds,but will do little for the LA combo with 2.45 gears, no matter what cam you install in it, with the factory pistons and heads . What I mean is with a power peak at 5000@57 mph,With that 262 cam, it takes to about 40 mph to find any significant horsepower that they might bring to the table, and then comes either the speed limit or the shift, and you are back in the basement@2800rpm.


    For your car, you gotta look at the whole picture. The only thing that car has got going for it is the A999.
    And it's a pretty heavy car
    If your budget is limited, and you want to be quicker ,then yur kindof screwed.
    The Magnum is still a good idea, but the rear gears have got to go, and the cam and stall have to be considered together, just as the cam and compression ratio need to be considered together. and a 360M will make the car feel hundreds of pounds lighter.

    Happy HotRodding
     
    Last edited: Dec 29, 2019
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  7. beatersRus

    beatersRus Well-Known Member

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    im doing the exact same build currently on an 81.
    youll need the following
    parts from Your Original la motor-motor mounts,oil pan and pickup.

    Distributor..this is your call but they sell Nice 1 wire hookups over on ebay for less than a 100.
    a Magnum 4bbl; intake manifold...selling for 220 at summit.
    a standalone Fuel pump/electric,w pressure regulator.
    a Full gasket set.
    a New timing chain.
    a New water pump.

    things you want to use.
    more than likely,you just pulled a magnum motor out of a truck.
    believe it or not,use the truck Exhaust manifolds.
    take the motor mounts,the oil pan and pickup off and swap them with Car pieces.

    Most important*
    make Sure that you keep and Reuse the stock Flywheel/on the magnum motor that Came With It.
    take the torque convertor and lay the flywheel against it you will see one hole is offset and HAS to be ground out enough for the 4th convertor bolt.
    do NOT use the la flywheel/flexplate!!

    do Not forget to Fully seat your torque convertor before putting trans on motor.
    it goes in Twice,youll feel it.
    spin the tq as you push gently inwards until you feel it go in Twice and then Spin it Both ways if you hear a click,then youve seated the pump drive and are good to go.

    tip,you can use older mopar valve covers just ignore extra holes.
    this opens up a lot of possibilities for dressing up your magnum motors.

    last thoughts,yes you can use a 360 magnum but it gets a little more expensive.
    Many thanks to AJ,for letting us know about the magnum cam timing as well.
    its a good day when you learn something new.
     
  8. AJ/FormS

    AJ/FormS Well-Known Member

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    As to the Magnum cam; I have never had one in my hands to measure.
    From many different forum sources and I cannot confirm this to be true; it seems to be like this;
    250/264/110/37* overlap; and 182/195@.050; .411/.430 lift.
    When installed as per what all the forums say, namely at 119 centerline, them you get;
    250/264/110+9/12* effective overlap/116 compression/127 power, Ica of 64*
    but straight up;you get
    250/264/110+0/36*Effective/129 compression/114 power extraction/Ica of 51

    Do You know why they do this?
    At least Two reasons, that I can think of;
    1) to reduce the cylinder pressure, so the engine can run pumpgas; and
    2) 13 more degrees of power extraction makes sure that when the exhaust comes out the tailpipe it is cold and has little to no energy left in it. That's good for fuel economy.... I guess; and
    3) since the engine is running log manifolds, and the overlap cycle is pretty much dead, they sacrifice it
    4) IDK how this affects the emission stuff.

    Lets put that cam into the 9.4 Scr 318M and see what happens;
    First as factory stock
    Static compression ratio of 9.4:1.
    Ica of 64 and 700ft elevation.
    Effective stroke is 2.57 inches.
    Your dynamic compression ratio is 7.51:1 .
    Your dynamic cranking pressure is 146.84
    PSI. ............................. 147
    V/P (Volume to Pressure Index) is 109 ......................................... 109

    next as cam retimed to zero
    Static compression ratio of 9.4:1.
    Effective stroke is 2.84 inches.
    Ica of 51*, and 700'
    Your dynamic compression ratio is 8.20:1 .
    Your dynamic cranking pressure is 165.15
    PSI. .............................. 165
    V/P (Volume to Pressure Index) is 135 .......................................... 135

    Wudyalookatthat!

    165psi is probably pushing the limits in a heavy car, but I would certainly give it a try with a Magnum; but no way in an open-chamber LA.
    But more importantly, look at what happened to the VP! from oil-burning 318LA territory (109) to warmed up 360 territory (135). That is a 24% improvement in performance from stall to about 3500 rpm. That is exactly like running 24% more rear gear. So 2.45x1.24=3.04s. That is how it will feel to you. Keep in mind, with 2.45 gears and a 2.74 low, 3500rpm is about 40 mph so this torque improvement is a very big deal.
    Or you could think of it also a running up the power curve and finding 24% more torque. Let's say your 5.2 made 150 ftlbs at 2200 (63hp), I'm just saying. With the retimeed cam add 24% and I get 186 ftlbs still at 2200, but now 78 hp.See that! like 15hp from a cam retime. and it's right where you need it, namely at stall.
    but what happens to the rest of the program?
    The only thing that got worse is power extraction... but you still have more than enough left over for a streeter 114* is plenty.
    The effective overlap jumped from 12* to 36* so headers are gonna increase your power throughout the powerband, and on the 110 LSA, it will make a nice lil boost at the power-peak. There is no downside to this retiming ............. unless the engine detonates itself to death. Your job will be to see that this does not happen, and you do it in the tuning. There are several options open to you.
     
    Last edited: Dec 31, 2019
  9. BudW

    BudW Moderator Staff Member

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    If you need a car to drive while in the parts gathering/building mode, then finding a Magnum 5.2 (or 5.9) would be good to do. After built, it could be swapped out in a weekend.
    If car must be down for repairs for a while and you have other transportation, then other things do open up.

    For bang for the buck, the Magnum gets you most power for least $. Many things can transfer over, some things will not. Fuel injection (factory Magnum or aftermarket) would be really nice, but also mean more things to change to get engine into vehicle and running.


    I’m in a very similar boat with my ’86 Fifth Ave. It is using a bit of oil (valve seals are shot, and every gasket is leaking) in addition it also has very little get up and go. The bigger reason is the 2.2 gear ratio.
    My ’77 wagon has same engine, transmission and about same weight vehicle - but has 2.9 gears in it. The wagon will do circles around the Fifth Ave from a take off. It also is a lot more – no wait, loads more fun to drive in town than the Fifth Ave is – all because of the gear ratio.

    I have a ’84 8¼” differential with 2.9’s to put into the Fifth, after I rebuild and paint it (look for a forum post about this in the coming months – after it warms up, that is). That in of itself will transform that car into something a lot more streetable and be more withstanding of future power upgrades.

    Now with that said, I just picked up a late ‘60’s 8¾” differential last weekend, so I might just build it for the Fifth. Either way, I can’t get rid of those 2.2’s fast enough.
    BudW
     
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  10. AJ/FormS

    AJ/FormS Well-Known Member

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    My father's 84 Fifth, which I inherited, was a great Hiway cruiser; but as you might imagine; it only needed low and hi, cuz 65 mph was 4000rpm in first gear. Well second was used for passing, every now and then.
    I briefly considered spending money on it as the body was very nice, but at 60 years of age, I reasoned that it would never happen.
    It took two years to move it off the yard.I let her go to the first guy that offered money.

    I installed a stock smoggerteen into my Barracuda every winter 5 in a row, with nothing but a 4bbl and headers; she was my winter engine. One particular winter it ran with an A833od with the GVod behind it and 3.23s. 65 was about 1400rpm in double od.
    The thing I actually liked about that combo, was putting it into too-high a gear and then flooring it. Listening to the 318, TQ howling, laboring up to hiway speed thru dual 3inchers, at about the same rpm all the way,(7 speeds) was killer amusing,not to mention watching the time, tick-tocking...... away, lol. I used to lean forward, grab the 13" steering wheel hard, and pretend I was on a rocketship, heading for outer space, and the burn-time was in slow-motion, lol Hyup, good times. I was a lot younger in 2003 or 4......... lol.
     
    Last edited: Jan 1, 2020
  11. Ele115

    Ele115 Well-Known Member

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    A wrecked Jeep or Durango with a 5.9 should do.
     
  12. beatersRus

    beatersRus Well-Known Member

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    i sincerely hope that you are actually Reading the post i made.
    Before you just go yank a magnum out of a truck or a jeep and think itll drop in,
    with nothing needed extra..because..it wont.

    also,seeing as noone else bothered to pointed it out.
    you will need the La engine Timing cover as well.
    and,keep the magnum Balancer On the Magnum motor just bolt your pulleys to it.
     
  13. Ele115

    Ele115 Well-Known Member

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    Take everything from the wrecked one
     
  14. kingoftooland

    kingoftooland Active Member

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    The more I think of it I think I am gona go with a la 318 because I am not looking for a tire shredding monster I want a lil more power gona keep my 500 cfm carb n performer intake n get a pair of ally heads n a baby cam n a pair of headders
     
  15. Ele115

    Ele115 Well-Known Member

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    There is nothing at all wrong with a 318. I have several 318 weekend cars that I drive regularly and I enjoy them. Parts are cheap, but I rarely have to do much to them. They can be quite good on fuel. You can do a few things to wake up a 318 and still have a good reliable car that won't eat up your finances
     
  16. AJ/FormS

    AJ/FormS Well-Known Member

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    I think you missed the point.....
    the EFI 9.4Scr 5.2M is rated at 230 hp net, that could be as high as 270 crank
    It already has the right cam in it. and great heads for a teener.And doesn't need a compression boost.
    But if you put your 500 and headers on the 5.2M, well then,that will push the power to over 300crank, with, if you retime that funky factory cam, a very strong bottom end, just what you need.
    --------------------------------
    The 8.0 318LA is rated at about 150 net, could be 175 crank.
    your bolt-ons might bring that to 230 crank, with possibly/probably a weak bottom end, that is gonna require a TC to get past. The alloy heads may bring a bit more compression to the table, but at low-rpm they will also pull heat out of the chambers and heat is power, so below 3500ish and with hiway gears, they may actually hurt performance.
    The 8.0 baby-cammed 318LA will have less power at the top, but worse is that it will have a LOT less from idle to 3000/3500, which with hiway gears, is gonna hurt you bad.
    So if you are gonna go LA, then spend some money and bring the Scr up to match your cam and stay ironheadded to go with that baby cam.

    ------------------------------------
    To a streeter, peak power means almost nothing. But torque from stall onwards does.
    If your engine is dead below 3000 it don't matter how much power she boasts at peak; you still gotta get there to make use of it. And with 2.2s or 2.45s the getting up takes a really really long time. Peak torque on these engine is gonna be around 3200 give or take. The Hi-compression 252* cammed Magnum will be a lil higher. The lo-compression 240* cammed LA a lil sooner. So using 3200 and 2.45s, this comes to about 36mph with a 2.74 low gear. So you wait, and wait and wait, for the meager torque to show up, and finally the car starts to wake up. With 2.2s, 3200 doesn't come until 41mph.
    Ok so then get you a 3200TC and problem solved right?
    So Again I say; no matter what you do, you are gonna need a TC, and to get rid of those hiway gears........... so do yourself a huge favor, and just get that done first.
    You will have the biggest grin you can imagine,
    versus the worst frown if you go the route you are thinking of.
    I have done these kinds of swaps several times, and the guys who went gears and TCs are always excited afterwards. While the guys who went your way always cried about all the money they spent, just for less performance.

    If you need the hiway gears, you will NEVER be happy with the performance of either 318 ; unless you supercharge it,lol, but the 5.2M is still a better jumping-off point.

    I know what yur doing, your avoiding all the work of pulling the engine, aren't you........ Wait until yur 65 or 70,lol . So hire someone already. How much can it cost? He has the shop the lift, the crane and the tools. Just about 4 hours should do it. Am I wrong?
     
  17. Duke5A

    Duke5A Well-Known Member

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    If you're swapping out heads with aluminum ones and other parts then the advantages of the Magnum start to dwindle. LA motors respond to speed parts just the same as Mags do.

    Still though, 360/5.9 is still the route I would recommend. If you're talking about aluminum heads and a mild a build you're going to be disappointed. Take a 318 and 360, built with all the same components, the 360 is still going to produce more torque, and most importantly, make that torque lower in the RPM range. This greatly adds to drivability. No winding the motor out for when you do want power and you can run a much lower numerical gear. No high RPM highway driving.

    It's your build, do what you will, but I've had five motors in my car over the last twenty years. 318's just don't move heavy four door cars with keeping streetability in mind.
     
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  18. Oldiron440

    Oldiron440 Well-Known Member

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    It will be hard to equal the 5.2 M dollar for dollar warming up the 318 LA.
     
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  19. Camtron

    Camtron Well-Known Member

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    318 magnum would be the best bet off your original post.
    Your 84 engine has a garbage CR, late model 318LA’s don’t have a much better CR but, would be a better choice if you did want to go the route of building a 318la.
    The 318Mag is going to give you an instant boost in engine performance with minimum effort and dollars spent, the 360Mag would be even better bang for your buck and blow the 318Mag out of the water.
    For the type of driving and the additional parts you mentioned purchasing in your original post, I’d go 360Mag with a new gear set in the rear end and call it a day.
     
    Last edited: Jan 5, 2020
  20. Ele115

    Ele115 Well-Known Member

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    I get the impression this project is limited in scope by costs and time