150 HP LA 318 - vs - 230 HP Magnum 318
Do those numbers sound right?
Well that depends.
I see this is an old thread, but I'm gonna unload anyway.
The 150hp 318s were rated 8/1, Emission slugs with retarded timing, crappy heads, tiny 2bbl Carter carbs, and a restrictive single exhaust system. Being 1973; that 150hp was a net rating.
The 1972 engine, just one year earlier, was rated 230 hp, gross. It was rated at 9.2 Scr and, closed-chamber crappy heads, way better timing, a single-plain intake and a bigger Rochester carb.
The point is that if you are rebuilding the 318LA anyway, with new pistons, then the Magnum advantage quickly loses it's shine. If you already have a Magnum, and an intake for it, then it makes sense to use it; just don't use the factory cam.
But don't throw an LA away if it's what you already have.
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But if you have neither, you know what I'm gonna suggest right ....................... it costs the same for machining any SBM regardless of size, and the KB107s for a 360, drop in at about .012 below deck, so with .028 gaskets you already have a flying headstart on anything else SBM; no matter which direction you take it.
From there, everything else SBM can be installed, including the smog-era crappy 318 heads..... altho, that would be throwing away the Tight-Q advantage.
And besides all that, the 360 falls together with a nice modern high compression ratio real easy, so you can run a pretty good sized cam, and not need a stinking hi-stall, nor race gears in the back, altho for street duty, the big cam and 2.73s are not the hot ticket.
Just try to make 185/195psi with a 318 and you'll see what I mean, whereas with a 360, it's harder to not exceed those numbers than to sneak up on it. And I guarantee you that, that when running such hi-pressure, on the street, you will not care one bit about the size of the cam.....
Meh, some people will aver that you don't need big pressure on the street. Ok fair enough, it's true you don't. But if you end up at 140psi or less, two things are gonna happen;
1) If you come from running say even 185, you are gonna be one sad SBM owner; and
2) now you gotta throw another wagon-load of cash at it, to try and find the smile that the hi-pressure engine used to light up your life with. But no matter what you throw at that low-pressure wanna-be SBM, that smile is just not forthcoming. You will buy a hi stall, and big rear gears, perhaps multiple times, and see your fuel-mileage plummet into the single-digits, while the hiway cruise rpm will drive you nuts, and on and on it goes.
Look,
building a high-pressure 360 will cover all the bases and, relatively speaking, is at least as cheap, or cheaper in the long run, as band-aiding any smaller engine, with a suitable convertor and gears, which will still never compare to a hi-pressure 360 anyway.
Well unless you supercharge your smaller engine....... but there goes the budget.
Dear Mopar HotRodder, do yourself a favor; if considering a low-compression/ small displacement style engine, you might as well budget an overdrive right from the get-go. So now, you can run a proper stall and gears to get the rpm up to where it needs to be, to have fun with, while simultaneously being able to drive it anywhere anytime. Then gear the daymn thing to run outta power at around 55/60 mph in Second gear, but build it to rev a good 10% higher, than it needs to, just so you can hear your stinking Mopar wind up!, and put some decent closed-chamber heads on it.
For instance to hit say 60mph at 5500 rpm with 27"tires, your car will need an overall roadgear of 6.63.
If yur running an A500, it has a Second gear of 1.54 so then, 6.63/1.54= 4.30s in the back. and with those,
65= 2400 in overdrive and Locked Up, badaboom!
Knowing this now, you can select an appropriate cam.
Having done that, you can now select the heads.
Having done that, you can now work out the Scr to maximize the pressure, so you can run as low, yes as low, a stall as will make you happy.
Now, I gotta tell you, when coming up behind a slowpoke doing 55 in a 65, downshifting from locked-up in overdrive, to into Third gear, your engine will hit just 3200 in direct at WOT, or 5000 in Second, so pretty much your best choice is Third gear. The thing is, at 3200, a NA lo-compression 318 with a modest cam pulls like pushing a limpdyk; you will only ever try that once in traffic.
Yur gonna want that hi-pressure 360, cuz when you nail it in Third gear, you will already be at 5000 rpm=85mph as you fly by the driver, and see his stunned expression. I know this is true because mine does that with 3.55s lol, all be it in Second gear, with a 4-speed, and at 7200/lol.
Now;
meh, some will say you don't need a 360 to have fun with, on the street, and that's true. But I say, if yur gonna spend the coin, yur gonna get way more smiles per dollar out of the hi-pressure 360. And you can tell all your friends, who are gonna insist that the 340 is the king of smallblocks, to kissyurazz. Just ask any hi-pressure 360 owner if they ever regretted not having built a 318. Don't ask a 318 owner, their egos get in the way.
Doing it any other way IMO, is just looking for disappointment and/or a never-ending parade into and out of the shop, do-overs, or finally, getting a hi-pressure 360.
BTW
Yes I have, built 318s and owned several HO340s ; which is why I don't have one anymore, lol.
Meh!, it's only 42 cubes guys will say. Well, when yur sitting on the line, with your convertor pulling at stall rpm and my 360 has 13% more torque than yours right at the line, tell me how much you don't mind having 22 fewer cubes .......
Or; when you are screaming your 318 down the hiway at 3600rpm with 4.30s, and pulling 9mpgs, to my 367 idling at 65= 1600rpm in double-overdrive and pulling 30 mpgs; go ahead and remind me it's only 42 cubes.
Or; when my 367 pulls 93 mph in the Eighth, in Second-over, doing under 6200rpm, to your 318 hitting 93 in the quarter @5500...... remind me about the 42 cubes.
Or; remind me why guys install 4"cranks in 365s; It wouldn't have anything to do with the 40-odd cubes now would it?
Meh, lunkheads I say.
Happy HotRodding
PS;
can a 318 even pull itself at 65= 1600 rpm? IDK.
and if it can, how much throttle will it take? and
how do you give it the timing it craves?
I know with 2.20 rear gears 65=a tic under 1800, so that seems to be possible ..... but 1600 is still 11% slower ......
