340 Candidate? 1971 Dodge Demon

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In the wake of the successful launch of the Plymouth Duster (a Valiant fastback), Dodge lobbied for and got its variant, the Demon. The little car with the devilish name debuted in 1971 and was essentially a Duster with a Dart front clip. This first year’s edition looks faster than it would be with a Slant-Six engine but that motor has gone bad and needs replacing. This Demon 340 clone candidate is north of Fresno, California, and available here on craigslist for $9,500. A shout-out goes to Pat L. for another great Mopar tip!

It was not uncommon for comparable Dodge models to sell in smaller numbers than corresponding cars from Plymouth. In 1971, Plymouth built 186,000 Dusters while Dodge saw 80,000 Demons. But in 1972, while Duster output increased by 22%, Demon assemblies dropped by 39%. Dodge executives concluded that the name was the problem and that they might be alienating their church-going customers. So they changed the name of the product to Dart Sport in 1973. Same car, different moniker. That may have done the trick as output increased back to 80,000 units from 49,000. These numbers were for both the base models and the 340-performance cars.

With its black stripes, this 1971 Demon looks like it could hold its own in a stoplight drag race. But it won’t come close, even if its base 225 cubic inch Slant-Six engine was working properly. At more than 100,000 miles, we’re told the motor has a bad knock and will need to be rebuilt. A lot of would-be buyers might decide to use this as an opportunity to upgrade, to turn the car into a Demon 340 clone as these 275 hp engines are not hard to come by.

The body and paint (one repaint) seem to be nice on this Dodge. The only rust seems to be in the spare tire well in the trunk which could easily be patched. The same might be said of the interior, which looks fine except for the driver’s side seatback which is quite worn. But that shouldn’t be a big problem to overcome. This 52-year-old car has only had two owners, and no one has attempted to modify the car (at least not until now). If you stayed with a Slant Six, this would be a civil car to drive with an automatic transmission, power steering, and power front disc brakes (which would help with a 340 under the hood, too).

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  1. Slantasaurus

    Russ, apparently you aren’t too familiar with 340 engines, they are kind of hard to come by and expensive when you do find one. 360s are much more common and cost less. That said Id rebuild the Slant in this one with some parts and tricks Ive learned along the way.

    Like 8
  2. Rabbit

    I guess the real question here is “How did they manage to blow up a Slant Six?”

    Like 28
    • Paolo

      If you aren’t careful about oil changes and oil levels you can spin a bearing easily. Slant 6’s are very tolerant of neglect and abuse which allows owners to get the idea they need no maintenance at all. A warn out slant will toil along burning a qt. of oil every 50 miles with the oil light coming on at every stop sign for years. But if you don’t top it up or if you stupidly over-rev it you will throw a rod.

      $9500 seems a bit much for Demon with a rod knock, if that is the actual diagnosis.

      Like 3
    • Ed P

      The only way is to run it out of oil.

      Like 0
  3. Grant

    Slant six all the way, the world has too many 340 clones. A nice rebuilt six will out live all of us, and then some.

    Like 5
  4. Nevadahalfrack NevadahalfrackMember

    Yank the S/Six, set it aside for posterity and drop in a new crate HEMI 392! THEN build out accordingly with goos suspenders, discs on all 4, quiet cans-but set up with cutouts..

    Like 7
  5. Big Bear 🇺🇸

    I was on the fence about keeping the slant 6. Until I read knock in the motor. How is that possible on a Mopar slant 6? Forgot to put oil in after oil change? If that engine is done . Then stroker 406 6 pack with 727 and sure grip 8 3/4 with 3.91 custom driveshaft. Then you need to change the torsion bars to 340/360 all the shocks to a V8. Maybe re-arc the leaf springs. And patch weld the holes in the tire holder. That’s my take on it. No it’s not cheap but it will surprise lots of folk’s. Good luck to the next owner. 🐻🇺🇸

    Like 2
  6. Maggy

    My buddy bought our history teachers 71red demon with a slant 6 for 200 in 8th grade with permission of his parents.Whomever owned this example probably never checked the oil.I’veNEVER heard of a slant 6 with a rod knock.I’d go the 340 route but like someone else said they are not cheap or too easy to find.

    Like 3
    • Robert Holt

      I would have to agree with you about the bulletproof nature of the slant 6 225, my very first car was a ’76 Dart Custom with that venerable little motor. It would really surprise you, doing a lovely single tire burnout from a dead stop after pulling it down in 1st and romping the gas.. yeah I was one of those guys, I kinda still am. Although I still appreciate a good smoke show, I don’t do it in my 5-speed Silverado, cuz I depend on it for work, and I know the way my luck runs I’d surely tear the 350,000 mile clutch completely out of it. Plus I’ve got 400+ lbs of plumbing tools in the back, so no donuts either… and although I’ve witnessed some pretty phenomenal burnouts on Harleys, I don’t dare try it on my Fatboy, those little tires ain’t cheap either! But that little Dart was what I learned to drive in, and drift in (on gravel roads, if course), and I ended up breaking a couple of teeth out of the rear end doing neutral drops. Yeah yeah, I hear you guys all saying ‘monkey see monkey do’… but the little 225 was flawless when I sold the car, I even saw it a few years later, in a local parking lot, still had my Air Force sticker in the back window. I thought ‘man I miss that car but I’m glad she’s still going!’ But I also agree with big bear, I’d probably redo the slant 6 and squirrel it away for posterity and drop a mill under the hood of this little sleeper.

      Like 0
  7. Big C

    Slant Six? 340? 360? Oh Hail No! This car cries out for an LS-1!
    just kidding…

    Like 0
  8. Jay E.Member

    10+ years ago I had a 225 Demon with 4 speed. Yellow with black stripe. Great condition, no rust. Had it for around 7 or 8 years and didn’t use it much. A friend needed a car and so I sold it for 2K. Didn’t realize the market had changed since I bought it. $9500.00 for a blown engine one. Wowzers…

    Like 1
  9. Jay E.Member

    Color me…Gone

    Like 0
    • Harry

      And for a brief moment Gary was able to bask in the glory of the slant 6 option!

      Like 1
  10. Davey Boy

    Already sold. Bummer

    Like 0
  11. Mike Styles

    I’d go with a 360 4V just like on Roadkill garage.

    Like 0

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