LA 360 or Magnum 5.9

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texas360

texas360

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I've got a 1973 mopar with a tired number matching 318. Running a built 904. LA motors are getting harder and harder to find, but magnums are readily available. I want something around 320-350 hp. I hear it's alot easier to get with magnum motors. I know factory heads on mags are bad and the cam will need to be changed to a long snout or use a kit to create a centric on cam to run mechanical fuel Pump. Who has done this build or swap. Is it pretty simple and everything bolt up or should I just keep. Looking for a LA 360 to build.
 
T56MaxTorq said:
The roller cam ONLY is worth finding a magnum
Click to expand...
fixed it for you ;)

find a late LA, for a few years they came with the roller rockers
if you can find one of those you dont have to worry about zinc content in oil, cracked heads or what fuel pump you want to run
on top of that, there are many different options out there for LA intakes...magnums, not so much
 
You can put 1.88 valve heads on your 318 and 350 HP should be as easy as falling off a log.

The hydraulic roller is OVERRATED. In fact, I stopped using hydraulic roller lifters over ten years ago.
For what you want to do a decent hydraulic flat tappet cam would be more than worthy. If you don't mind lashing valves, do a SFT.

Use what you have.
 
Roller cam started somewhere in the later 80s in 318 and 360 LA engines. Magnum engines started in 91 or 92. I agree with yellow rose about the 318, since he already has it and goals don't require the cubes of a 360.
 
Also, the factory Magnum heads are not bad if you just install a running engine, they just usually have cracks around the valve seats, so you wouldn't want to spend money rebuilding Magnum heads when there is better replacements available.
 
As far as I can tell the Magnums seem to be at 9.588 deck heights and are said to be more consistently at that spec. That's a minimum .012 difference. And that just makes a zero-deck that much cheaper to achieve.
I haven't measured any, jus saying.
 
texas360 said:
I want something around 320-350 hp. I hear it's alot easier to get with magnum motors. I know factory heads on mags are bad and the cam will need to be changed to a long snout or use a kit to create a centric on cam to run mechanical fuel Pump. Who has done this build or swap. Is it pretty simple and everything bolt up or should I just keep. Looking for a LA 360 to build.
Click to expand...

You could run a cracked head a 100,000 miles and never know it. thecrackissue is overrated and blown out of proportion. Worth checking? Sure.

A 5.9 would require little cam to make those HP numbers. A small 224 -ish like duration @ .050 would be enough cam. Just get the cam and reuse the lifters and pushrods. Add headers, RPM intake and carb. Done.

IF you dont get theflexplate behind the engine, B&M makes one for the Magnum engine and a zero balance converter. Just a FYI there.

Here is an example of a cam. 20-811-9 - Xtreme Energy™ Retro-Fit Hydraulic Roller Camshafts
 
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I just got an LA 360 back from the machine shop and will be excited to hear it run. One more to build after that, but I am saving it for a rainy day. I find them from time to time here in my neck of the woods. Never looked for a magnum...
 
rumblefish360 said:
You could run a cracked head a 100,000 miles and never know it. thecrackissue is overrated and blown out of proportion. Worth checking? Sure.

A 5.9 would require little cam to make those HP numbers. A small 224 -ish like duration @ .050 would be enough cam. Just get the cam and reuse the lifters and pushrods. Add headers, RPM intake and carb. Done.

IF you dont get theflexplate behind the engine, B&M makes one for the Magnum engine and a zero balance converter. Just a FYI there.

Here is an example of a cam. 20-811-9 - Xtreme Energy™ Retro-Fit Hydraulic Roller Camshafts
Click to expand...

What Rumblefish said! It is sooooo easy to get those horsepower numbers out of a junkyard magnum. I have a lot of threads about mine. Also, the magnumswaps website is great! He is also a member on here and helped me a lot.

Not knocking LA engines, but at that power level its easy with a magnum.
 
I agree. Increased rocker ratio's help excite the cam action, OE 9.0-1 compression ratios, fresh, by compare cylinders with low wear, good heads and roller tappets.
the "LA" needs a rebuild up front. Not bad for a lot of reasons. But for a danm near bolt in and go, MAGNUMIZE IT!
 
doing additional research - the 360 era has some in-between years. The 1989/90 blocks have the bosses in the valley for roller lifter holds downs and continued to use the long snout cam. 1991 couple updates - basically the same with 1992 as the last of the LA blocks. These came with fuel injection and carbs.

There doesn't appear to be much after market support on these years - dont know why. Maybe just did test on these years? Maybe because at this stage this was a truck engine. All the information I found was on truck sites. Checking summit for head options - MP head or eddy victor (1985 appears to be the cutoff). Didn't look at other parts to change this low comp engine Maybe there are other options - but we know the more options and choices the better the prices

So for a drop and drive - pretty cheap engine. To hot rod it - it looks to be pricey. So for later era - late 80s-up - the magnum would be the better choice
 
So almost positive Im going to go magnum. Can't beat price of complete running 145,000 mile motor from my brother in law for $100. Then I just have to find an intake an oil pan, pump, pick up. Need to find out what cam I can upgrade to with long snout(for mechanical fuel pump) that has some power potential and it's got to be lopey or choppy. Also I have to see which flex plate I need to make it work with my 2800 stall that's currently behind my 318(no weights). I was also told as long as I use the LA front cover the power steering pump and alternator will bolt right up that's on. My. Current 318 LA motor.
 
@cudajames

You have to know your small blocks for those years that seem to have no support. Consider the divide between small blocks as you read about engines here. This is the easiest way to do it.
Poly 318
LA 273 - 318 - 340 - 360
Magnum 318 - 360

The roller LA engines can and do use all the LA stuff except the roller cam, lifters and pushrods. All other parts will swap out for older LA parts. Retro fitting is just as EZ as changing a shirt.
 
Make sure you get the stock flexplate with the magnum. Converter issue solved.

I made the hp numbers you are looking for at the tires with a small hydraulic roller cam and EQ Magnum heads. Thats over 400 on motor. Didn't touch the shortblock since it was drug home from the junkers.

Steve
 
You would have to do quite a bit to a 318 to get 350 hp.
even with new heads,cam,intake and higher compression pistons the small bore would still probably struggle to match and early stock 340 at 275 hp.
 
LXguy said:
Make sure you get the stock flexplate with the magnum. Converter issue solved.

I made the hp numbers you are looking for at the tires with a small hydraulic roller cam and EQ Magnum heads. Thats over 400 on motor. Didn't touch the shortblock since it was drug home from the junkers.

Steve
Click to expand...
Sounds like a plan. What about a pair of stock heads that are freshly redone by machine shop? Can't really afford EQ or rhs heads. I want to for sure change cam because I need the lopey or choppy sound
 
ir3333 said:
You would have to do quite a bit to a 318 to get 350 hp.
even with new heads,cam,intake and higher compression pistons the small bore would still probably struggle to match and early stock 340 at 275 hp.
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Negitive! At that HP level, 275, an intake, 220@.050 cam with matching springs and header set up matches the 340’s track times.
Stock heads, low compression.
Been there done that.
 
Yes on the LA timing cover, as those have mechanical fuel pump mounting provision and Magnum cover does not. LA timing cover will allow LA power steering brackets, water pump, alternator, and pulleys to be retained, once you slot one of the crank pulley bolt holes. Same for the flex plate if you use the Magnum plate.
 
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