Oyaji

. That's good to know about the reliability and longevity of the B-series Cummins engines. In that case I agree that need not be a fear when boosting its power. . It will sure smoke a lot more - but in a state that doesn't care, that smoke may add a certain perverse pleasue to driving a diesel! :D Economy will suffer in proportion to the increase of smoke - but sometimes it will no doubt be worth it just for the visual effect!. :rotf: . . Regarding aerodynamics - your VW TDI example not only has less frontal area but also a much lower coefficient of drag than a Comanche. You're right in your suspicion about its 80+MPH capability being tied to its aerodynamics. Gearing choice depends on power required to equal load demand, so the VW as an example isn't a good one to use in helping to choose.

. It's an option - but the more you turn it up, the more you lose advantages of economy and longevity. . On a mechanical injection fuel pump the easiest way to boost power and torque is to simply increase the charging pump pressure (by turning up the charging pump pressure regulator adjustment - usually all it takes is an Allen wrench and a couple turns or less). You can also fiddle with the timing fairly easily; fiddling with the advance requires disassembly of the pump (best left to a specialty shop). . One job I had to work my way through college was to rebuilt pumps and injectors in just such a specialty shop. I wouldn't want to fiddle with them, at least not beyond maybe turning up the charging pressure a little... and even then I'd want to do it on a dyno (~5% gains or so, 10% max).

. Naturally aspirated - 60 horsepower. Turbo version - 85 horsepower. Torque about the same as the 4.0 Jeep engine, at ~220 pound-feet. . Torque is fine, but with so little horsepower your top speed will be limited to 65 MPH or a bit more, I think. Acceleration will be slow (painfully slow for someone accustomed to gasoline-powered engine performance). Hills will be challenging at high speed. Climbing long grades at speed will be impossible: you'll have to gear down. Is that acceptable?

Thanks for the ideas guys. I really like the stuff you are coming up with. The ideas I think have the most merit so far are the cam change in the 4.0, the Volvo/AW4 match, and the 2.4 DOHC/6-speed with 231, as they would seem to offer the most bang for the the least work. . One thing to point out is that even if another car demonstrates a certain stellar economy with a given engine, swapping that engine to a truck will NOT yield similar results. Since the shape is different, the aerodynamic load will be different (pick-ups generate horrid drag!), and thus will the gearing required for efficient running be different (note that weight has almost no influence on economy at highway speeds, though it does in stop and go urban driving). In the extreme case, a given engine might not even be suitable at all no matter what the gearing is changed to, simply because the torque and power curves may be so incompatible with the application so as to be unable to offer acceptable performance over the complete operating envelope. . Here is an example. Fella I know was hot to make an entry into the Automotive X-Prize for fuel economy a few years back. To even qualify, all entries had to demonstrate a minimum of 100 MPG. He had custom mounts fabbed (at no small expense) to mate a 17 hp Yanmar 3-banger to a VW-based dune buggy and was sure he was in the running. Early on in the project, via an introduction by a mutual friend, he approached me to help him get an estimate (this was when I accompanied him on the initial trip to the machinist). When after some guesstimation and figuring on scrap paper yielded an estimate of 65 MPG at 40 MPH and a top speed of around 55 MPH, he was furious with me, held faith in his belief (he had no facts to base his belief upon), and I nearly had to walk home! Months later when he had built the thing and the performance fell far short of the requirements to enter the contest, he never spoke to me again... nor would he admit his fuel economy results to my friend, either. I saw him on the road with the thing a couple times that first year, backing up traffic for a quarter mile... but that buggy has been sitting in his yard for a couple years now. If it still runs, it ain't getting any use at all anymore.

. Interesting. . But how much torque does such a little engine put out? Maybe enough to pull a trailer with the 6-speed - but not a heavy one, I reckon... I'd like torque in the ballpark of the 4.0 if possible, and that means a diesel (or re-camming a 4.0 as Eagle suggested). Still, if it has variable valve timing, it might do significantly better than the stock 2.5 on both torque and economy. The 2.5 is already capable enough if you are not in a hurry, right? So this option is worth a closer look I think.

I was thinking about trying this, as a matter of fact. . You might have to fiddle with the centering a bit - check it on the smooth wear surface of the drum so you don't get out of round grinding down the lip. You won't need much speed - idling engine will do. Try to come up with some blocks to use as a jig/brace to hold your grinder steady, and take care not to get long sleeves or anything else caught, else we may not be hearing from you again! . It goes pretty fast depending on your grinder, so it pays to be slow and deliberate in your work as you go.

You could bolt the drum on backwards, start the engine, drop it in gear, and use the rear end and drivetrain as a lathe. If you do this, take all safety precautions of course, and use Jim's grinding method. Keeping the drums balanced will be less of an issue with them rotating.

. Most plastics are safe from brake fluid (it ships in a plastic bottle, after all). Are you saying the plastic fuse block itself will wash away in brake fluid, or just the tar backing?. . Eagle mentioned corrosiveness - I thought he was referring to the terminals of the fuse block. Anything that is corrosive will by definition carry electric current, so the fuse block terminals are in double jeopardy (as is the surrounding sheetmetal - like the floorpanel - because it is grounded to the battery). The threat of dissolving the plastic fuse block and having it puddle on the floor makes it triply bad (I had never seen nor heard of this) - quadruply so if you consider the resulting fire risk. . I guess the choice of plastic for fuse block plastic was a poor one if it dissolves like paint in contact with brake fluid. I wonder if there is a replacement alternative that would weather DOT3 - and why NHTSA never forced a mandatory safety recall.

. DOT3 brake fluid isn't in itself corrosive - it's the moisture from the air that DOT3 absorbs that causes the corrosion. (For that matter, water isn't itself corrosive, but rather the dissociated ions that water picks up in solution that are.) Since DOT5 doesn't absorb moisture, you don't have that problem, which is I think the best reason to use it in a street car.

. Good call. . Unlike DOT3 brake fluid which absorbs moisture out of the air, DOT5 is silicone-based and doesn't. That alone is good enough reason to use it, besides the fact that its boiling point is something like 3 times higher. . There are 3 problems I see with DOT5. First is the price - the stuff was $32/quart last time I priced it (and it was a while ago). Next is that you cannot mix it with DOT3 fluid - so any time I am replacing major components I consider changing over to DOT5 (you're supposed to clean the DOT3 out with isopropyl alcohol and compressed air). Last is that it doesn't like fast bleeding. Any rapid agitation in the presence of air will mix tiny bubbles into the fluid, which take months to get out. Best way is to slowly back-bleed with low pressure from the bottom to the top.

. That info about diesel options for AW4 and AX15 is tantalizing. I'd like more details, so I'll start Googling. If you have more to share, please add it here if you have the time and inclination - thanks!

. WOW. . That there is as good a testimonial that ATF won't destroy an engine as you will ever hear, I reckon. I would still be worried that it might soften the seals too much, but still, this particular engine seems to have tolerated the ATF very well. . I am curious - after the ATF incident, did the oil leaks subside any?

. Nope, no noticeable power gains... but remember, that engine was near the end of its life. But when I did pull it down for overhaul a few months later, it looked like new inside - there were no deposits built up anywhere. (Remember, there were 2 inched of sludge built up under the valve cover a few months earlier.) Even the piston ring grooves were spotless (though stained), as were the passages behind them. There was nothing to clean out of the grooves, though I tried using a broken ring to scrape them out just to be sure - not even a little coke remained there. I used the same pistons since they mic'ed out within spec (as did the cylinder bores - could still see the original hone marks everywhere), and just put in new rings. A couple of the rod bearings were showing copper and I swapped them for new ones, but used the same main bearings (crank and rod ends mic'ed out good too). . I just fired that engine up last week (after the truck it is in sat unused in the barn for the last 20 years) - needs a bit of work on the carb (idle jet is plugged at least), but once I redo that and the brakes and put on new tires I think I'll put it back on the road. :)

. Has anyone tried a CV joint drive shaft (to replace the U-joint(s)) to alleviate that problem? Certainly more expensive - which would be "Chiseller's" management's rationale behind cheaping out on the concentric damping weight - but perhaps the best fix?. . [And re the name "Libertine" - :rotf:]

I'm not big on either Sea Foam or Marvel Mystery Oil - I put both in the "snake oil" category. But the one thing I see they do accomplish - removing sludge from an old engine - I get in a different way. . Here is a tip I picked up from a master mechanic I worked for to make money for college after I left the farm: every couple years and just before an oil change when the engine oil is a quart low, add a quart of automatic transmission fluid and drive under light load for 50-75 miles. Make sure the change the oil and filter that same day, just as soon as the engine cools enough that you can. . This works wonders. I had the proof of it firsthand the very first time he talked me into it. I was adjusting the valves of my old 1972 Datsun pickup, and was scooping enormous gobs of sludge from the valve cover, wondering about how to get all the crap out from under the separator chamber below the PCV, when he walked past and asked WTH I was doing. When I replied that I was saving time by cleaning the valve cover up now so when I did my planned overhaul in a few months then I'd have that much less to do, he laughed and told me I was wasting my time because there was a much easier way to get it clean - and told me the ATF trick. When I was incredulous and voiced my fear that it would dilute the engine oil too much, he pointed out that the trick was not to leave the ATF/engine oil mix in there for very long and to drive under only light load. . Well, he finally convinced me to try it. When I drained the oil a little later, it looked like Hershey's Chocolate syrup! The compression went up across all cylinders (a little - about 5 PSI IIRC - likely from de-sludging gummed-up rings), and when I pulled the engine down a few months later, aside from a little grainy residue in the oil pan that wouldn't drain out with the oil, it was spotless inside. That included the half-cleaned valve cover, which I had put back on the engine with 2 inches of sludge still stuck to the underside but was now so clean I could see all the scrape marks from where I had been gouging out chunks of the sludge with a putty knife. Further, rubber engine seals that are normally pretty stiff and brittle after 200,000+ miles felt lively and nearly as soft as the new ones Ireplaced them with! My boss attributed that to the different composition of ATF. He said the superb cleaning action resulted from the detergents used in ATF, but I am unsure on that - I was thinking it could result purely from the thinning of the oil. Whatever the cause, there was no arguing with the results. . That very first experience made me a believer. I suppose you might get similar results from diluting the engine oil with anything, but I'll stick with what I and people I know well have experience with. Those solvents scare me off, to tell the truth.

. OK - the binding issue is as I guessed. I expect that adding a leaf will help, but won't cure the problem, because the lurch you feel is under deceleration, and axle wrap is far less an issue then than under acceleration. Getting stiffer front springs might help more, since the weight shift forward under braking causes the rear to rise while the rear end stays on the ground, causing a driveline geometry change that has your yoke sliding out a bit and binding upon return to level unloaded suspension position. . That doesn't fix the root cause. Though having the annoyance go away will probably restore your peace of mind to some degree, if you are like me then you will still be bugged by the knowledge that there is still something inherently wrong with the design... .So what is the vibration issue? I was guessing wear would allow the yoke to wobble a bit on the splines, thus causing vibration. . I see Chrysler had the grease idea, but I wonder if the dealership packed enough inside the yoke. I also wonder if they used molybdenum CV joint grease, and if it wouldn't be a good alternative, and if a couple shots through an added grease fitting every so often wouldn't help even more.

Exactly as I expected and described - so what is the problem with lubrication then? The grease is not up to the task? Or there is no easy way to add more? If so, that was why I proposed adding a grease zerk.. Otherwise, what sort of grease is used to lube the splines? Maybe a swap to a specialty grease would help - like CV joint grease - its molybdenum content and high-pressure qualities might alleviate the problem. Another alternative would be universal joint grease, if you can get it - it is a specialty high-pressure grease also. U-joints fail without it, and that is the reason that manufacturers no longer incorporate grease zerks: the special grease they are assembled with is not generally available and regular grease isn't up to the task, so nowadays they come with no zerk to add grease so as to not adulterate what is packed inside from the factory.

Nope, the vibration is a result of u-joint angle combined with unsupported length of tailshaft. It affected ALL XJs with the Up Country suspension. I know -- I own two of them. I discussed it with the service manager at the dealership where I bought them, and he admitted that his wife's '99 XJ had the same problem. The factory did offer a "fix." Not a short shaft conversion, which would have been a real fix. No, the factory wanted to just install a transfer case drop to change the u-joint angle. The vibration isn't too bad on my wife's 2000 with the 242 transfer case, so I'm not worried about that one. My 2000 5-speed has a severe vibration, so I baby it when driving, and I have a short-shaft conversion sitting in the garage waiting for the day (week) when I can find the time to install it. The output shaft lubrication issue causes a different phenomenon -- a short of "lurch/bump" feeling coming from the drive train just as forward motion stops when driving and then stopping (such as a t traffic lights). I get that a lot more in the 2001 than in either of the 2000s. Eagle - what's the lubrication issue? That the splines on the output shaft and inside the slip yoke are not in a bath of 90-weight? And if that, are the splines binding and wearing for lack of lubrication?.. If so, seems like the addition of a grease zerk and the occasional shot of grease through it into the slip yoke might fix that? It works for other driveshafts on much heavier equipment... or maybe I am misunderstanding your description of the problem.

I remember that commercial!

WINNAR!

If you get it cheap enough, it would be worth having around for some future project - hell, you could at least run a welder/generator with it if nothing else. . Did you ask the seller how much it weighs? Maybe he knows...

I agree. So how do they balance the 5-cylinder engine you're looking at? . That's a good question, and one that occurred to me also. IIRC, the first and second order harmonics are not as bad in an I-5 as in a V-6 (though not ZERO as they are in an I-6), so maybe they get by with only counterweights. But ultimately, longevity speaks for itself. The OM 617 I-5 has gone a million miles without overhaul! . When I started this thread, it occurred to me that there might be a suitable gasoline-powered OHC V-6 with variable valve timing out there, but it would have to be a really good'un to capture my attention. But a diesel, on the other hand...

.That is getting to be a pretty strong engine. I bet it has sufficient torque to make frame-twisting a problem. Kinda overkill for a little ole Comanche? . I really dislike the idea of a V-6 design with counterweights and balance shafts replacing any inherently-balanced I-6, but I guess if the right V-6 came along it would merit consideration. I never heard of this 3.0 V-6 diesel - I guess it is a bigger version of the 2.8L CRD V-6? Wiring is awfully complicated on the 2.8L CRD, from what I saw... but I guess that would be a mighty sweet package when done. I just don't see myself doing it, nor being able to afford to pay someone else to do it for me (at least not any time soon).

. I thought about getting what they call a "half cut", which is just the front half of an XJ cut off and shipped here from overseas. Evidently it is the easiest way to get what you need. The beauty part is that since it cannot be put on the road, it is classed as "parts" for import. Would probably need to get 2 though, just to have a parts source! I wonder what the total cost would be including shipping... . Cost seems to be prohibitive for any diesel alternative, but for someone who intends to keep his vehicle on the road for the long term (like a Comanche owner, for instance :)), I figure that eventually fuel savings would pay for the swap. . Eagle's cam swap idea seems to make the best sense so far, practically and financially. But I can't help but think that a diesel would be the perfect swap for a 1986 with a 2.8L V6.

Whoops - was posting in the other window I had open, in the wrong thread - trying again here. . Interesting comments so far guys - keep 'em coming. . I am gonna toss out my choices one at a time and let you pick them apart. Let's start with the OM 617. Pros: acceptable performance in automotive application (revs fast for a diesel), a lot of them around, reasonable price, great reputation for economy and longevity. Cons: not-so-hot-horsepower, it's a non-stock conversion, needs adapter plate, a little heavier than the 4.0 (iirc 600 pounds), old diesel technology (maybe this is a pro, not a con?). The OM617 engine family was a straight-5 Diesel automobile engine from Mercedes-Benz used in the 1970s and 1980s. It is closely related to the straight-4 OM616. Starting in 1978, a turbocharger was fitted to engines used in the 300SD. With some Mercedes-Benz 300D/300SD diesels already exceeding 500,000 miles, and a few nearing 1,000,000, the OM617 is considered to be one of the most reliable engines ever produced, and is one of the key reasons for Mercedes' popularity in North America in the 1980s, as it was economical, relatively quick (compared to most other diesels on the market) and was trouble-free, unlike the Oldsmobile LF9 diesel V8. . The OM617.951 was introduced in 1979 and displaced 2998 cc, using a 90.9 mm bore and 92.4 mm stroke. Power output was 125 hp (91 kW). Torque was rated at 180 lb·ft (244 N·m). Applications: 1981-1985 300SD Turbo 1981 300TD Turbo . Then there is the VM 2.5. Pros: lighter weight, used overseas in stock XJ application, good torque, mechanical injection. Cons: hard to get in the USA, ditto for parts, just-adequate anemic horsepower. 2.5L TurboDiesel VM 425 2499 cc (153 CID) I4, OHV Diesel 114 hp (85 kW) @ 3900 rpm 221 lb·ft (300 N·m) @ 2000 rpm VM Motori 425 OHV 1994–2001