• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

5.2 magnum motor vs old school LA motor

dsd1967

Well-Known Member
Local time
4:49 AM
Joined
Mar 6, 2011
Messages
932
Reaction score
523
Location
Toledo
Not B body related....but you guys always have the answers. My son has a 79 power wagon with a 318 that is in dire need of a rebuild. He just found a 5.2 magnum on FB marketplace that is fresh out of the machine shop with at .030 over, short block reassembled and heads ready to bolt on for $700. If it is what it says....he's money and time ahead getting this motor. I know there are differences such as the roller cam, the pedestal rockers and the intake/head bolt pattern. What other potential pitfalls would we run into if we decided to make this changeover.

- Are there 4bbl manifolds available for the magnum motors?
- Will the ancillary parts bolt on (distributor, waterpump, engine mounts, PS and alternator brackets...or did they revise any of those locations and mounting holes
- Does the distributor need to have a different drive gear material vs traditional distributors
- Are the valve covers different

This is my first endeavor into a magnum motor.....any insight would be helpful. I know they had the better flowing chamber designs, hardened seats and there are a lot of upsides....I just need to know the pitfalls and how big of hurdles they are.

Thanks
Dave
 
Lots of accessory differences. Mags used a serpentine system on the drives. Nice setup. WP is reverse rotation. No provision for mechanical fuel pump. Balance may be different between LA and Mag. Has roller cam but not sure if dist drive is different. Get one for a Mag to be safe. VC's are different. Edelbrock and another company have an intake. Swapping on LA accessories may be a challenge. Since it's a Mag and not a Hemi, you may be able to score the accessories from a yard for a good price. This book may be of assistance.
Mopar Performance Magnum Engines
 
Last edited:
Thanks ckessel! A little more involved vs just unbolting from one and bolting onto another, but not show stoppers. I'll have to dig a little deeper into this.
 
forabodiesonly.com is the place to look for info. They even have a magnum swap section.
 
The 5.2 magnum is internally balanced so you should be okay there. Just use the oil pump drive gear that came with the magnum engine. You will need a distributor with mechanical and vacuum advance.
 
Last edited:
The switch from the LA to the Magnum designation was evolutionary. They addressed several areas where improvements could be made. The Magnums are a superior design. The roller cam was a great change. The 10 bolt valve covers seal a LOT better than the LA versions. The 5.2 and 5.9 used the same heads and they flow much better than LA castings. No LA series 318 was ever rated over 170 NET HP, even the short lived 4 barrel engines . The 5.2 was rated at 230 through a catalytic converter.
 
Last edited:
The 67 318 2bbl was rated at 230.
They went to net in 72 I believe.
 
Gross versus net is an apples to oranges competition.
 
The 1999 Dodge Dakota R/T claimed 245 HP with the 5.9 Magnum. Very little difference between a Ram Van Engine and the Dakota R/T engine. The difference was the tune on the ECM for the R/T and the exhaust. Other than that it was a run of the mill 5.9 Magnum. Mopar used to make a M1 intake for the engine. Which was costly. I paid nearly 600.00 for a 4bbl intake. Hughes makes an intake for the Magnum or atleast last time I looked they still sold them. The Harland Sharp 1.7 Roller Rockers, Headers, Mopar Performance ECU and a 52mm Throttle body woke the 5.9 up.

DSC00004.JPG
 
Thanks everyone for the feedback and links. From the Hughes site, it looks like I should be making a close inspection of the heads as they are prone to cracking, but not too much else concerning for a conversion from one to the other unless I try to do heads interchange from new to old...which isn't in the plan.

I now have a lot of information and opinions to make a better decision. I'll pass this on to my son since he's footing the bill.

Dave
 
Actually I believe there's no difference in a "regular" 5.9 and a 5.9 in an R/T.
It's just the "big engine, small truck" thing.
I LOVE mine, BTW.

Also no one has mentioned that 67-69 318's are 9.2:1 compression, then 8.8:1 until the LA rollers where they were back to a much more truly measured 9.2:1.
Seems like nearly everyone forgets this.
 
Actually I believe there's no difference in a "regular" 5.9 and a 5.9 in an R/T.
It's just the "big engine, small truck" thing.
I LOVE mine, BTW.

Also no one has mentioned that 67-69 318's are 9.2:1 compression, then 8.8:1 until the LA rollers where they were back to a much more truly measured 9.2:1.
Seems like nearly everyone forgets this.
Same engine.. Different tune with the R/T PCM and exhaust.
 
When I worked at the dealer, back counter for the dealer tech's, they went through many of those heads due to cracking. We used 4-6 pairs per week. BeepBeepRR, did you get your M1 from SoCal Dakota? If so, I most likely sold that to Sam.
 
No I bought it through Mancini Racing. My truck and I were on DakotaRT.com for a while. That is where I watched and learned about the making power with bolt on stuff. I wanted to do a 408 stroker with it but my money was thin as it is now. So I just did the common bolt on stuff which was still expensive. 600 for Harland Sharp Rockers, 600 ish for the intake and 300 for the PCM as well as another 900.00 for Doug Thorley Try Y headers. I forgot the 52 mm billet TB. Forget how much I paid for that. All that and reduced my fuel economy to 9mpg lol. Sure was fun getting it up to speed though.
 
Last edited:
Charlie/aka Ckessel pretty much nailed it. I'd do a magnum every day of the week over an LA unless I was going for originality.
They look very similar (not like plunking a gen3 in there), have plenty of aftermarket support and will bolt into any LA-equipped car with the proper mounts. A big bonus IMO is that the scrapyards are overflowing with them...so along with the engines themselves a lot of the ancillary parts can be bought cheap, cleaned up and re-used.
Better flowing heads and factory designed for roller cams...'nuff said!
 
The freedom to run regular oil is tempting.
 
Auto Transport Service
Back
Top