MPG Motor Magnum vs. Hemi

Discussion in 'Magnum Engine Swaps' started by slicknapier, Feb 20, 2018.

  1. slicknapier

    slicknapier Well-Known Member

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    Kind of a weird question and vehicle is definitely not an A-body, but this section seems to be the most knowledgeable out of all the different forums. I have a 62 Chrysler New Yorker Wagon with a tired 413 that in the near future would like to do an epic old school coast to coast family truckster type vacation. Say you had a $3000-4000 budget to do a newer injected motor swap what would you choose? It will definitely be injected and I already have a solid lockup 518 for the swap. Not looking for a 500 hp motor, but something I could possibly squeeze out the most miles per gallon in my big ole boat. I have a 2000 5.2 I’m my daily 63 Dodge Crewcab and love it. I look forward to get peoples opinions. Thanks!

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    • Pascamp

      Pascamp Well-Known Member

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      I've owned tons of Magnum and Hemi powered trucks and vans. Mileage ranged from abysmal to horrifying. My wife has owned a few Hemi cars and they all got mid-high 20's on the highway. All of those were 6 speeds though. I suspect the trans is the reason. Never owned a Magnum powered car (don't even know if they made one).
       
    • DFX 340 Duster

      DFX 340 Duster FABO Gold Member FABO Gold Member

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      Rebuild the 413 and stick the long ram induction system on it. It was made to give optimum power at highway cruise!
       
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      • toolmanmike

        toolmanmike FABO Staff Staff Member FABO Gold Member

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        I vote to keep the 413 also. A little RV cam and late model EFI type fuel injection would work well. Mileage depending on what rear gear and tire size, I would estimate mid teens at least on a highway haul. You could always mod a o/d tranny or the like. That 413 could pull any gear combination. Nice wagon!
         
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        • abodyjoe

          abodyjoe Well-Known Member

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          if you are set on a more modern engine then i'd say the 5.7 hemi would probably return better mpg and power.
           
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          • myduster360

            myduster360 FABO Gold Member FABO Gold Member

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            5.7L with EFI definitely has more potential for decent MPG. If a little more effort is made, you maybe able to leave the MDS enabled to run it in 4cly mode at light cruise

            5.7 from a truck mated to its 5speed Auto would be my choice for a decent mpg daily.
             
          • JDMopar

            JDMopar Well-Known Member

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            A newer Hemi would get better mileage, but there's no way to do it for 3 or 4K. It's a nice swap to do, but expensive as hell !
             
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            • thesiren74

              thesiren74 Well-Known Member

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              413 fuel injected and a gear vendors o/d.
               
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              • KosmicKuda

                KosmicKuda Well-Known Member

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                If you are set on an engine swap I'd vote for a 5.2 or 5.9 Magnum BUT you need O/D to maximize MPG. O/D will yield more mileage than EFI. A Dodge truck has what you need and Hotwire may be able to help.
                Or freshen the 413 with a Gearvendors.
                 
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                • Pascamp

                  Pascamp Well-Known Member

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                  As others have said, I'd keep the engine and do a trans swap. An acquaintance had a 3rd gen Camaro with a Caddy 500 and an overdrive (probably a th200 or 700). He was getting high 20's mpg and that thing was bad fast for a street car in the early 90's.
                   
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                  • mgoblue9798

                    mgoblue9798 Member

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                    If mileage is the primary concern, a magnum 360 will make max torque 1000 rpm lower than a 5.7 hemi. Build the 360 with some Kb107 pistons and magnum heads set up for .040 quench and mileage and torque will both go up from a regular factory motor. I don't think the hemi is even an option for most people with only a 3-4 k budget.
                     
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                    • slicknapier

                      slicknapier Well-Known Member

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                      Thanks for all the suggestions. It’s a pretty tough decision. I love the 413 and push button, but I just feel it would be tough to get the mileage up in to the mid-high teens? Tires will probably stay 14’s with factory 3.23 gears. I can get a 5.7 hemi here locally complete for $1500. Magnums can be had around $500. Then the cost of the fuel and computer system . I will look more into the gear vendors as well.
                       
                    • mgoblue9798

                      mgoblue9798 Member

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                      You could check to see if there is a quench dome piston made for the 413. They do make them for a 440. They can be used to set up quench with an open chamber head and greatly increase efficiency.Keith Black KB Performance Pistons KB184-STD
                      You could also have the 413 set up with zero deck pistons and get a set of a/m closed chamber heads to do the same thing. This set up combined with a well tuned thermoquad shout do mid teens for mileage in your wagon with no problem assuming your able to keep your foot out of it.
                       
                    • sccachallenger

                      sccachallenger Well-Known Member

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                      And all the little stuff that really adds up! Read some of the 3rd gen swap threads $$$!
                      Freshen the 413, or swap in a 383/361. Run a 2.76 gear and add aftermarket efi.
                      The new Hemis are great, just pricy to swap at this time, hopefully it'll get better soon.
                       
                    • DFX 340 Duster

                      DFX 340 Duster FABO Gold Member FABO Gold Member

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                      I have a 5.7 Hemi in my 2007 Charger RT. I get 15 mpg around town when I really use a light pedal. I can get 25 on the highway with cruise control and the system running on 4 cylinders.
                      Back in the 1970s, I was able to squeeze 18 mpg highway out of my 361 big block in a B-body by using a 2.76 gear ratio and keeping the vacuum in the "economy" range.
                      I agree with the guys who say the best money spent for gas mileage would be on an overdrive unit/tranny.
                       
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                      • 1994redram

                        1994redram FABO Gold Member FABO Gold Member

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                        Rebuild the 413 and find a big block bellhousing to use that 518. You should be able to stay below your budget that way. You could also go with a Holley, msd, fitech, fast, etc aftermarket EFI for around $1500.
                         
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                        • SSVDP

                          SSVDP FABO Gold Member FABO Gold Member

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                          I’m thinking transmission will make the biggest difference.
                          The 5.7 Hemi advantage is the msd ( cylinder deactivation). The 5.2/5.9 magnum runs rich at any sort of load over about 3600 Rpm with stock calibration to keep the ridiculously cheap exhaust valves cool.
                           
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                          • 67Dart273

                            67Dart273 Well-Known Member

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                            I see no reason why a 5.2 should not get really decent mileage. "Back in the day" a friend had a 318 2bbl Charger (68?9?) that routinely pulled down 19 or so

                            I swapped a bone stock 71 340 into my 70 RR "back then" and later added headers. Even with my "uncareful" driving it would get 17.5.

                            These RAM pickups are HEAVY. Even my "White Whale I" the 97 1500 2wd was near 5K or so I never drove it "highway" enough to get any sort of baseline, it was high mileage and I used it mostly to tow.
                             
                          • RustyRatRod

                            RustyRatRod Just another dumbass. FABO Gold Member Technical Editor

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                            Fantastic car and cool idea! Not to rain on your parade, but no way in hell will you accomplish your goal for 3000-4000 dollars. Ain't happenin. Double it. Then you might be close.
                             
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                            • harrisonm

                              harrisonm Well-Known Member

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                              Why not rebuild the 413 and put a tall highway gear in the back and go with a carb. THAT you might be able to do for your budget IF you can do most of the work yourself.
                               
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                              • toolmanmike

                                toolmanmike FABO Staff Staff Member FABO Gold Member

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                                Another great idea! Nothing wrong with a late model HEMI it just could be more involved and expensive.
                                 
                              • 273

                                273 Well-Known Member

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                                Its hard to recoup dollars spent on gaining mileage. Especially a summer only car.

                                Your better off just putting the dollars into the gas tank. It could take decades to recoup $5000.

                                If you do a lot of highway driving OD is a decent value for performance and mpg gain.
                                 
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                                • slicknapier

                                  slicknapier Well-Known Member

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                                  This is a fun topic with a lot of great advice and ideas. I did the magnum swap on my Crewcab for about $600. I used everything I could off the donor and fabbed up the rest. It has been the single best thing I’ve done to the truck. It had 139,000 miles when I put it in and I’ve put about 30,000 super reliable miles on it. That’s what has me on the fence about the 413 that probably needs a rebuild. I could probably have a magnum in it running for under $1500 which I feel would be equal to the rebuild cost? Just trying to weigh my options.
                                   
                                • 273

                                  273 Well-Known Member

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                                  Smaller engine doesn't necessarily mean better mileage especially if your looking for a bit of performance to go with it.

                                  If you plan on going OD a 5.2/5.9 would be a good choice since it bolts right up.
                                   
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                                  • Pascamp

                                    Pascamp Well-Known Member

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                                    The 413 definitely has the cool/weird factor though, and no amount of money can add that to the Magnum.
                                     
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