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.
all I am really gona do is get a master rebuild kit from summit and maybe a mild cam n a set of headders
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