1971 Dodge b100 dajiban (possible MZR/ SJ6AEL swap)

Still in the "I just drug this thing home, now what?" stage.

 My original intent was to swap in a 2.5 MZR/ Fusion  (with needed oil pan and pickup swap/ balance shaft delete) and 6 speed manual. I have since been giving some thought to possibly using an automatic from a Miata due to the shifter location and the fact that there is an interference issue with my left foot and pretty much everything near the clutch pedal (size 18 feet).

The van is a complete base model with power nothing and no interior beyond the front seats, so I'm guessing it is still going to weigh about 3700-3800lbs post-swap- which is a far cry from the weight of a MX5. 

I guess my question is:

How much abuse will the MX5 (SJ6AEL) put up with, and does 3800lbs with a stock 2.5 exceed that?

I'm hoping someone here might have some info, because, thus far- google has been useless.

I'm going to chime in and hopefully it comes across as my opinion of this idea without any reflection on you personally:

I generally like engine swaps and weird projects. The big car - small engine - direction = The opposite of what makes sense to me. I don't think the Miata engine swap would be better in any sense than any of the factory offerings for the van. 

Is it all pieces that you already have?

Is the goal weird for the sake of weird or something else? 

In reply to GoLucky :

The goal for the van is to be just a cool parts hauler with about the same power to weight as a 90's minitruck. The engine that is currently in it is a 225 that hasn't run in over a decade, and the compression test I ran on it doesn't bode well for it (70ish psi on all but #2, which had 90). The transmission is currently held up with a ratchet strap, and I'm missing some of the clutch linkage, so I figured I'd swap it.

Swapping a Mopar V8 into it has a few disadvantages, mainly that the LA series V8 hasn't been produced in almost 20yrs, so any example I find is likely going to need a rebuild (or at least freshening up), and you're stuck with a Chrysler automatic transmission to put behind it (see also: rebuild, upgrade or very expensive standalone for the 8hp), or an adapter plate to put a GM transmission behind it. Most stock (or nearly stock) 318 magnums only put out about 180hp at the wheel, with about 230 ft/lbs of torque, and are fairly thirsty to boot.

Swapping in a LS would make significantly more power, and allow a decent transmission selection, and I am kicking around the idea, but then it's just "another LS swap".

Rebuilding the 6 is entirely possible, but the amount of money needed to be sunk into it in order to move the van at a reasonable pace would more than pay for a V8 swap.

MZR (duratec) 2.5 makes 170ish HP, 170ish torque at the wheels in a Miata (about double the HP, about the same torque as a 225, almost the same HP as a stock 318 magnum), new enough to get a low mileage unit, small enough to fit in the van's engine bay and be pretty easy to work on, and has a few RWD automatic transmissions that can be bolted to it (Mazda 6 spd, Ford 5 spd, Ford 6 spd, Ford 10spd). It also can usually be had for about the same price as a camshaft for a Mopar V8, or what Holley charges for LS swap mounts.

The reason I asked about the trans is I had a lead on a wrecked NC (2009) a few months back that had one in it. My thinking was to buy the car, sell the 2.0, and swap a boneyard 2.5, that trans and the harness/ ecu/ tcu into the van, but I couldn't find any info on the trans, so I (stupidly) didn't jump on it. 

I realize that looking at if from a pure displacement standpoint, it does sound kinda dumb- and If I were building a hot-rod, the MZR wouldn't be anywhere near the top of the list. All I am looking for is "easy to work on, easy to get parts for, capable of keeping up with modern traffic, and cruising at 70", so "same torque, twice the power and twice the gears for the same cost as rebuilding what's there" starts to make a bit of sense.

Cool. I have swapped and owned a number of swap cars. Some of them were "another LS swap" but still very enjoyable to drive and build. Also just rebuilt a Dodge 46re auto too, so I can feel the concern about the Dodge transmissions. 

Genuinely hope it is a fun project that meets your goals. My concern with the MZR is not with the quantity of torque or power, but more where those numbers happen in the RPM range as compared to any of the stock engines. Heavy (comparative to donor chassis) plus highway gears in the rear end may end up un-fun to drive.  I suppose that if you invested in re-gearing the rear end you could make up for the higher peak torque and HP.

I had a JDM b18c (Integra type-R) swapped 1st gen CRV that had more torque and bunches more HP but it all happened at high rpms. It was still a fun car , I seem to recall hitting 80+ in 2nd gear. It would have been even better with either much lower gearing or more torque and HP lower in the rev range. 

How about other modern(ish) engine or trans families from truck/suv/full size car donors? Off the top of my head: Nissan VQ's or GM Atlas 4,5 or 6 or  Toyota UZ should all be up to the task. Probably some ford stuff too. 

Just thoughts. Stoked for whatever you end up going with and please put up your van pics. 

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In reply to GoLucky :

I have looked into A LOT of other options, The Issues I have found are that whatever it is has to be rear sump, and the dimensions of the engine bay (and doghouse cover). The rear sump thing in unavoidable, and while there are many rear sump conversions most of them cost as much as an entire engine that doesn't need the conversion. The rear sump thing rules out the majority of Japanese car V6's, the 3.5 Chrysler V6, the Atlas 6cyl, pretty much every Mercedes engine, and the Honda K series.

The other limitation is the shape of the engine bay/ doghouse cover. A Jeep 4.0 is too long, VQ35 (depending on intake) is too tall at the rear, VQ40 would have ground clearance issues with the Frontier pan, the 5.6 Nissan V8 is both too tall and wide, etc. Lol, Like I said I have looked at a lot of options.

I thought about the 5cyl Atlas, but I haven't been able to take any measurements off one, The 4cyl Atlas isn't any more powerful than the 2.5 MZR- so I'd probably pass on that one just due to the cost (or lack thereof) compared to the Mazda/Ford unit.

I also thought about doing a Pentastar swap, but after the debacle that trying to tune my daily has turned into (I swapped the 2.62 diff for a 3.90 unit from a scat-pack challenger, and the ECU lost its dang mind) I would rather shoot myself in the face with a nail gun than deal with another late model Stellantis ECU.

Going by the dyno sheets I have seen, the MZR isn't really that peaky. It seems to have most of its torque by 2500, which should work (should being the operative word) pretty well with an automatic- yet another reason I'm leaning that way. It's likely not going to set anyone's hair on fire with acceleration, but I'm hoping it'll be enough to do 0-60 in the sub-10 second range.

The van currently has a 3.55 ratio (or at least that's what's on the tag) in it, and I plan on lowering it and running a fairly short tire (less than 25" so that I still have a little bit of bump travel in the front), so the cruising rpm works up to be 2000 at  70mph. A re-gear to a 4.30 or 4.88 might be necessary (4.30 brings it up to 2400, 4.88 to 2750), but given the condition of every other fluid I have removed from the van, it's probably gonna need a rebuild anyway.

I still have a while to figure it out. The current project is to get it moved from the street in front of my house where we unloaded it, to my driveway off the alley behind the house. Haven't decided if it's going to be easier to try and reassemble everything and limp it there under its own power, or try and find a way to shove it with another vehicle (my driveway is pretty steep) without destroying both in the process. There's also the matter of the rag joint being totally shot (not so much a steering wheel as a suggestion wheel), and brakes that look like they haven't had fluid in them since the Reagan administration, so like I said, I have plenty of time to figure it out.