So, the slant in my B150 cargo has a SERIOUS rod knock--see recent associated posts. Although it would probably be easier to just drop in another slant (In fact, I actually already found a long block in the near that's already been completely rebuilt by a local machine shop and never installed--still has a warranty even), I thought it might be worth exploring the 4.0 Jeep conversion option. The van gets a far bit of abuse doing a lot of towing and hauling through the coastal mountain ranges, so the extra power would definitely come in handy. I haven't looked around much yet, but I'm guessing I can find a complete donor Jeep with all the associated control units and wiring for a reasonable price.

Of my six vehicles, not including motorcycles, my van is the only automatic. Simply put I don't trust 'em. However, one of the buying points for me on the van, apart from the slant and the price, was the 727 Torqueflight. A forth gear would be really nice, but I don't know much about the reliability of the Jeep autos, and I'd give up a gear not to take chances. Anyway finding a donor vehicle with a bad auto trans seems my best route.

I'm guessing that mating-up the 727 requires at least a bellhousing change, but beyond that, is it straight forward, or even possible? Talk about any other serious considerations concerning the engine or trans is very welcome. The nice thing here is that it's a van, so clearance issues are less an issue, I'd think. And they'll be lots of room to work once I dismantle the front end to pull the engine out. I've read it can go out the door, but my B2150 Kubota is my dedicated engine puller, and the loader forks won't fit through the door.

Short answer, no.

I don't know why you don't trust automatic transmissions. The 904 and 727 are aomg the most rugged and reliable automatic transmissions ever made. Properly adjusted with the correct fluid they will give very dependable service for hundreds of thousands of miles.

Neither the 904 nor the 727 has a removeable bellhousing. You would have to fabricate an adapter plate and a crank spacer, plus extend the kickdown linkage.

Save yourself a lot of money and frustration and just put in that long block you found. While the motor is out, replace the front seal on the trans, adjust the bands, change the filter, and adjust the kickdown properly once the motor is back in.

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Casually looking for a Clifford hyperpak intake for cheap.

AMC actually used the 904 and the 727 in the 70s and 80s, behind their own inline 6s. The case and bell housing are cast as 1 piece so an AMC version won't work with a Dodge /6 or V8. Unless you get new enough that you are talking about a MAGNUM V8 which by then is the same as the equivalent Dodge engine except they put the starter on the opposite side. But the 4.0 is different than the V8 bell housings. That 4.0 would bolt up to the older 232/258 AMC trans though.
And I believe that the trans mounts on the older AMC 904/727 is in the same place as the equivalent Dodge trans. So that would locate the engine and transmission in the right place if you did swap out the slant for a 4.0.

But putting in another slant 6 would be the easiest way out, and you're only gaining 17 CID going to the 4.0
Not enough to go to the trouble. Look around here, power upgrades are out there for the/6, money saved by not having to seek out parts that do bolt up to the 4.0, and no headache of having to have custom made motor mounts, you're better putting in another /6.

Yeah, what ☝︎those guys☝︎ said.

I would also like to gently point out that the odds are overwhelmingly against successfully going directly from
I don't know what these ports and things are on my carburetor, or what might be making this noise I hear

to
I'm gonna swap in a completely different kind of engine.

Even if it were a kind of engine that's known to fit the vehicle, and for which all the ancillary parts exist and don't have to be fabricated or modified, that's a giant job with many, many ways to go wrong. Make it an "alien" engine with zero precedent and zero existing parts to put that kind of engine in that kind of vehicle, and severe doubt that the engine will even fit (probably too long), and it turns into a quick, direct route to the van never again moving under its own power.

To get an idea of what it's like to swap a 4.0 into a vehicle not designed for it, see this very very long thread.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yeah, I guess I was sorta hoping someone would talk me out of it, unless it was pretty much a snap fit and go. Worth asking, I guess. Now I won't have to wonder.

But.. while we're on the subject. How different is the 4.0 head vs. the slant in terms of manifold ports? Specifically, is there any chance the 4.0 exhaust headers I see for under $100 on eBay could fit the slant? If it's a matter of bolt pattern, or misalignment, I also find a guy that sells plasma cut 1/2" mild steel header flanges for the slant that would fix that problem. I do a lot of welding and fabrication, so a little bending and tweeking is well within my purview.

The AMC-Jeep I6 has a completely different port arrangement. If you're looking at Jeep exhaust it should be obvious. Just for a start the two center ports on the 4.0 are exhaust and the 2 center ports on the 6 are intake.

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Joshua

I haven't looked closely at either, which is probably obvious. So, definitely not bolt up and go.

But.. bear with me here.. you've still got a collector with six header pipes of about the correct flange angle and port size to work with, and a flange that does fit the slant for about $100. Knowing what you know about the relative placement and spacing on both motors, would it be out-of-the-question (or just stupidly time consuming) to cut the pipes at the original flange and near the collector, and then re-weld them on the new flange and at the collector--bending, tweeking as needed?

Clearly I don't care at all about looks, equal length, etc. Anything that even resembles a header has got to be a huge improvement on the stock exhaust manifold. Also, it has entered my mind that the exhaust pre-heats the intake runners, which I know is pretty important for cold running. It doesn't take that long for an engine to warm up in Portland. And worst case, if I do have a problem, I'll wrap some 12v heat tape around the intake runners, and connect it to a toggle switch to pre-heat, like glow plugs on a tractor.

You're deluded.
I'm out.

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Joshua

Okay, thanks for your input, Josh.

Sounds like I should post a few photos of some of the stuff I've fabricated over the years, so you guys know I'm not just interested in wasting your time. Fair enough. I'm new here, I suppose I'd wonder too.

To be honest I could fabricate the header out of black pipe with a torch and a vice, flange included, if I decided to do so. I'm just attempting to think out-of-the-box a bit here, and take advantage of something that's cheap, and ready-made in China.

I think I speak for many people here by saying that I try my best to AVOID "made in China"

Sigh. I'm going to tackle this so that hopefully no one wastes any more time and energy than I'm about to.
No. The Jeep exhaust manifold has a flange with the wrong length (the AMC I6 is longer), wrong port arrangement (explained previously), even the wrong port shape. The tubes are in shapes you don't want running in directions you can't use to a collector location that looks to be inside the /6 crankcase.
This isn't a 'tweek'. You can completely cut up the Jeep header and you'd end up with maybe 1/2 the tubing you need to make a header to approximate the short Clifford headers and still not have head flanges or proper collectors.
The stock exhaust manifold is not nearly as bad as a many people think. To get a huge improvement in engine performance takes more than just nice exhaust tubing.
The exhaust manifold is open at the top of the collector area to directly heat the intake manifold directly under the carburetor. This is important for cold running, emissions and engine life. Did you know I grew up in Portland driving slant six cars? I can tell you exactly what happens when a high school kid mills the hot spot off the bottom of the intake manifold and drives the car around in cold, damp, Portland weather.
Yeah, you're fully deluded. The amount of heat energy needed will not be provided by your alternator let alone heat tape.

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Joshua

If you want to build your own header buy the flange pieces that you mentioned earlier and a universal exhaust header pipe kit and have at it.

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Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

Wow, now that's a detailed and insightful reply. I do appreciate it. Philosophically I agree with the "made in China" sentiment, but realistically half the crap everyone purchases daily comes from China. And so it goes, modern life in the 21st century. Anyway, are you going to tell me you never shop at Harbor Freight?

Re: high school kid doing stupid stuff... and burning A LOT of extra gas in the process. I've got those stories in droves. Like the time I put a 4.88 rear gear and an 850 double pumper on my 1970 1/2 Trans Am (my high school ride in Farmington Hills, in the burbs of Detroit, cir. 1979). Of course, it had the cam and manifolding to match that combo, but yeah, it used some gas. Went stop light to stop light down around Gratiot and Woodward reasonably quickly however, until I stripped all the teeth off 3rd gear. In those days seeing a Chevelle with SS 454 on the fender was so frequent it wasn't worth noticing. Whining GMC 6-71s, got most of the attention.

My username "Sportscarclinic" comes from the shop I used to own and run in Charleston, WV, before moving to Portland. At the time, it was the largest, independent import only shop in the state. Most of my 'expertise', if I can claim to have any nowadays, is in imports, specifically Subaru, and formerly Porsche. I've got a fair bit of content on Quora, mostly answering questions about engine operation, etc. Here's an example:
https://www.quora.com/Is-it-true-that-e ... a-mechanic

To speak to an earlier suggestion that I need help figuring out an engine knock, and/or finding ports on a carburetor, yes, I did. One thing I've figured out over the years is that people with hands-on experience with a specific make, can frequently save you hours of 'learning' and frustration. Could I have figured it out on my own, sure, eventually. I already had the same suspicions as to the cause. But one of the other things I've learned, is not to diagnose the problem for your mechanic, when you're the client. I provided as much, or as little, evidence as required to allow more experienced minds to come to, hopefully, the right conclusions.

I can go on and on here, but hopefully I've introduced myself sufficiently. I like the slant, always have. It's a engineering marvel for its day. So, I'm going to try to contribute here with my own journey into actually the first Mopar I've ever owned--always a GM guy back in the day, it's what dad drove, until he bought a 280ZX.

Returning to the header discussion now, concerning lack of intake preheat, condensation and lean mixture during cold operation, etc. Just out of curiosity, how do aftermarket intakes manage this problem, especially with headers? In other words, there's a solution somewhere, maybe it's not heat tape.

I did take a closer look at the Jeep header this morning, and noticed, now, that the exhaust ports are round, as you pointed out. So, yes, that claim was incorrect. Sounds like you're dead-set, and very possibly correct, about the manifold not working, so I'm not going argue otherwise. Sure anything can be made to fit, but at what cost of time and energy. I asked the question here, again, to tap expertise and save time.

Actually I found the Jeep header and flange while doing an eBay search for a universal header kit, so, yep good suggestion. But, looking at the Jeep header, and how cheap it was compared to the kit, got me to thinking...

Yes.

And I mean it.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.