Will a GEN III Hemi fit into a 71 Demon engine bay? Will stock suspension work?

New Hemi Engine Swaps

  1. a34

    a34 The Etowah Flash

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    Hey Guys,

    What needs to be done to make a GEN III Hemi work in a 71 Demon? Will it fit in the engine bay without cutting? Will the stock suspension support it, or does it need beefed up? What about maintenance of the engine afterwards, can you work on the thing?

    My son is thinking of doing this with his car and I'm not sure how easy of a swap this is. Would appreciate some practical real world advice from guys that have done it.
    Thanks!
     
  2. mvh

    mvh FABO Gold Member FABO Gold Member

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    It can be done with A-bodies, though I don't know of any Demons. I am familiar with one 67 Barracuda with this swap. There should be a lot of info if you search the forums. Not a trivial undertaking, but yes, you can use the stock suspension and k-frame, although I think a lot of people go to coil springs. TTI even makes headers for this swap. The main point of interference, as I understand it, is at the firewall.
     
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    • 408 swinger

      408 swinger FABO Gold Member FABO Gold Member

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      • 70Sbird

        70Sbird Possessed by Demons

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        My 71 Demon:
        Yes and Yes.
        Crate 6.4, original slant six K frame, Schumacher conversion mounts, Borgeson power steering box, TTI Headers. I redrilled the mounts to move the engine 3/8" forward so the SRV would clear the firewall and had to notch the RF framerail for the alternator. I'm also running the low mount A/C compressor so I had to modify the rear of the compressor a bit and clearance the K frame in that area. I will still need to find a spot for the remote mount oil filter, but I'll need to put the sway bar and front suspension on to see what is the best options for that location.

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        Last edited: Apr 1, 2021
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        • KosmicKuda

          KosmicKuda FABO Gold Member FABO Gold Member

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          The physical block size is the same for 5.7, 6.1 and 6.4. The flow numbers for stock Eagle heads are phenomenal.
          It's a fact that a dressed 5,7 is about 70 lbs lighter than a small block Mopar. Aluminum heads, plastic intakes, etc.
          Not much maintenance needs to be done, theoretically comparable to a new car. Logan's Cuda has something like 50,000 miles on his swap.
          There are LOTS of documented builds here. Spend some time reading.
          Hotwire and Mopar Performance have plug and play kits. If I had to start over, I'd go with the Holley Sniper Hemi setup which wasn't out when I started.

          I'll tell you right now. Hemi and cheap never appear in the same sentence.
           
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          • toolmanmike

            toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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            • loganscuda

              loganscuda DON’T reMember

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              Only maintenance I’ve done is oil change and plugs. It is no difference than any other engine for the most part. More room to work than in new vehicles. As far as fitting it depends on what year and what the motor is out of. I have a truck motor and the accessories are all up top ie: alternator compressor. The car motors are at the bottom and a few small cuts have to be made. The biggest problem is what transmission you use. I have a 2005 ram 5.7 and transmission with factory ECM. THE HOTWIRE harness is unbeatable the trans tunnel required cutting as the trans is enormous. You will have to do extensive research on what combo you want and ease of control and install. The New Hemi Swap forum is the only place you find out. There are guys who have done every combo in there. You just have to figure out what is best for your son. It will be confusing at first. But if you don’t research it right he would blow a bunch of money. He will need the basics; fuel delivery, headers engine control, new driveshaft, oil pan. I did the most efficient way for me I could. Used motor and trans from a truck $2500 (this was 2009)
              Harness $1000
              Headers $800
              Fuel tank w/fuel cell 800
              Shifter $175
              Electric fan $150
              Radiator $180 (Dillans Radiators)
              Motor mounts ?
              Fuel lines ?
              Trans cooler ?
              ECM $75

              Labor - free (sleepless nights drunkenness, anger issues, depression)
              There’s still quite a lot I’m sure I left out.
               
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              • loganscuda

                loganscuda DON’T reMember

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                • JDMopar

                  JDMopar Well-Known Member

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                  It's not all that hard, and a Gen III fits pretty nice. I was doing the swap to a Duster, which has the same engine compartment as a Demon. I had it all mounted, and then got sidetracked by a remodeling project that just had to be done "RIGHT NOW" :rolleyes: and then just lost interest. I have everything he needs to do it, minus a wiring harness. Not trying to start a for sale ad, but I don't want it anymore...and it's just sitting! PM me if he gets pumped up about doing it.....we don't live that far apart. :)
                   
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                  • mopar65

                    mopar65 Well-Known Member

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                    My Friend has a stroker gen 3 hemi in his 71 duster. He is useing TTI headers and a QA1 frame.

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                    • a34

                      a34 The Etowah Flash

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                      Thanks Guys for all the great info guys!! I have forwarded to him for review!
                       
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