Diesel Demon

[03TKMRacing]

I’m definitely far into the project to be posting about the car but I have a 1971 Dodge Demon that I am swapping a 6.7 Cummins from an 09 Ram 3500.

Originally the car was a slant six 225 with the 904 and 7 1/4. I thought of turboing the slant six, ls swap, and even a 2j swap but ultimately I wanted a Cummins. I started with a 12v block and got the engine mounts in, oil pan cut, trans mounted, radiator moved in front of the support but the 12v just didn’t seem right. I always wanted to do a 6.7 build but they were always too pricey. That was until I found a great deal on an engine from a wrecked truck with an upgraded turbo and was meticulously maintained.

I then found out that the 6.7s are a lot bigger everywhere than a 12v. The oil pan is wider and the crank/rods dip below the bottom of the block and the valve cover assembly is a lot taller too. Surprisingly when I remade the engine mounts I was able to get the engine to sit lower and further back this time. I clearanced the floorboard crossmember to fit the large 47re and made a bolt in tranny crossmember that also works as crossbracing to triangulate the subframe connectors I made.

For suspension I installed all the QA1 goodies; upper/lower control arms, strut rods, k member. I plan on getting a large sway bar and some shocks other than KYBs. For torsion bars I got 1.20” from SwayAway that are roughly 480inlbs spring rate. For steering I have a borgeson quick ratio ps box and I’m going to make my own center link/tie rods to clear the oil pan but keep the correct geometry.

The rearend I will eventually minitub and swap to a 9” (I know it’s not an 8 3/4 or a Dana 60 but I’m going for ultimate strength and really tall gears). For now it’s just got the 7 1/4 so I can get the engine and trans tuning good for easy driving and make it a solid cruiser.

There’s honestly a ton I’ve done to the car and I can’t think of everything off the top of my head but I plan on posting about it more often now so hopefully I’ll remember more later.

 

[clementine]

torque and traction = sub frame connectors. cool build!

 

[BigStrok3]

I like it.

 

[ch1ll]

I really like the trans mount from the trans tail to the frame rail connectors.

 

[azaustin]

Ok folks, don’t want to hurt anyone’s feelings, but this is what REAL hot ridding is all about. Going where no one’s gone before and doing as much of it by yourself as possible. This is going to be a really cool car when it’s done. Please keep us posted. Oh, the tire smoke…

 

[JDMopar]

DANG!!!! And the hood even shuts. There was a guy a few years ago who swapped a Cummins 4BT into a 72 Dart....but I can't remember if he was on here, or Moparts.com. Good job on the swap.

 

[Kern Dog]

Diesel stuff is popular now but I can't get excited about them given how they sound and smell.
I know that there is a world out there outside from V8s but they don't interest me for my own cars.
Turbo 4 cylinders, Supercharged V6s, hot rodded slant sixes and diesel engines are all capable of spanking many of our V8 cars but to me, they just sound strange.
I still respect the skill level needed to make them run. Good luck with the build.

 

[qkcuda]

That Demon looks like my first car, it was the same colour, and a slant six also. Cool build. Can't believe the hood actually closes.

 

[72bluNblu]

That's an 1,120 lb engine, dry. That's 300 lbs heavier than a Gen II 426 hemi. Even with the front suspension upgrades you have planned the sheer physics of the thing is going to make handling less than ideal. Guys run 1.20" bars with small blocks for road race and autoX applications. I run 1.12" bars on the street with a small block, and they're not anywhere near too big. And thats with almost half the engine weight up front. I think you're going to need to do more to that QA1 K and suspension components if you want them to live longterm. Not trying to be negative or anything, I have the QA1 LCA's on my Duster. But after seeing how the old CAP ones failed (bad welding), I gusseted my brand new QA1's even for my car. Probably overkill for me, but with the kind of weight you'll have up front I'd be looking to gusset the K and control arms further. Do you have additional chassis stiffening planned beyond just the subframes and crossmember? I would think you would need additional chassis work up front for all that additional weight.

If you're interested, here's the work I did on my QA1 LCA's, as well as some pictures of the failure on my CAP LCA's (QA1 bought CAP, the design of the LCA's is the same, but the production is much better).
My "new" '74 Duster- or why I need a project like a hole in the head

It also looks like it will be a dramatic reduction in ground clearance, based on the pan and how low the transmission mount appears. Maybe that's just the angle of the picture, but what are your plans for ride height?

Your fabrication work looks great, and I definitely appreciate the skill it takes to get as far as you have. Not sure I understand this one at all though, the size and weight of the thing is going to make life difficult at every turn. Literally and figuratively. Still I'm looking forward to seeing the finished product!

 

[03TKMRacing]

That's an 1,120 lb engine, dry. That's 300 lbs heavier than a Gen II 426 hemi. Even with the front suspension upgrades you have planned the sheer physics of the thing is going to make handling less than ideal. Guys run 1.20" bars with small blocks for road race and autoX applications. I run 1.12" bars on the street with a small block, and they're not anywhere near too big. And thats with almost half the engine weight up front. I think you're going to need to do more to that QA1 K and suspension components if you want them to live longterm. Not trying to be negative or anything, I have the QA1 LCA's on my Duster. But after seeing how the old CAP ones failed (bad welding), I gusseted my brand new QA1's even for my car. Probably overkill for me, but with the kind of weight you'll have up front I'd be looking to gusset the K and control arms further. Do you have additional chassis stiffening planned beyond just the subframes and crossmember? I would think you would need additional chassis work up front for all that additional weight.

If you're interested, here's the work I did on my QA1 LCA's, as well as some pictures of the failure on my CAP LCA's (QA1 bought CAP, the design of the LCA's is the same, but the production is much better).
My "new" '74 Duster- or why I need a project like a hole in the head

It also looks like it will be a dramatic reduction in ground clearance, based on the pan and how low the transmission mount appears. Maybe that's just the angle of the picture, but what are your plans for ride height?

Your fabrication work looks great, and I definitely appreciate the skill it takes to get as far as you have. Not sure I understand this one at all though, the size and weight of the thing is going to make life difficult at every turn. Literally and figuratively. Still I'm looking forward to seeing the finished product!

For chassis stiffening the trans crossmember mounts to 6 points. The rear most ones were visible in the pic. Then two mount in line with the trans and the last two actually go forward right before the frame curls up. A little further back I have a drive line loop made of 1 3/4 x .090 tubing. I do plan on adding some bars in the front wheel wells from the bottom up to the shock tower and after I get the new valve cover and other things routed I’ll build a strut tower brace that’ll tie into the radiator support.

As for ride height I set the car down with the adjusters set about halfway threaded in and added another 200 lbs to the nose to simulate fluids and any missing parts (and I also rolled the car back and forth a bit to get true ride height) then measured the height and bounced on the car to feel the ride. It came out the same as stock height wise and was stiffer than stock. The pan does hang down lower than stock but still has more clearance than my parents Mazdaspeed Miata does and I’ve taken that down a few fire roads for pictures.

I am going to take a look at how your beefed up your control arms. They’ve always looked a little on the weaker end. As for cornering I don’t plan on doing any road courses. Mostly straight line stuff. The car handled pretty crap to begin with since all the steering and suspension was original and had been used as a daily by the last owner so really it can only go up.