Originally Posted by whiteXj2

Well to be honest the Om617 is a tractor motor lol..more so than our 4.0's. Its a 5cly, and with the stock injector pump it will make around 250ftlbs max..after that you run out of fuel. At that point its time for meth injection or to have Myna? mod the IP (injector pump) for around 1500. And that will get you as much power you want! I prefer meth injection as it will make more power, keep the motor clean (think steam cleaning) & lower EGT's & IAT's.
Anyway they can achieve mid-high 20's...don't expect that much in a lifted jeep however I'd say 22-24mpg would be achievable..basically same jeep, with a 4.0 would probably get 18mpg, while the Om617 would get 20-25mpg. The benefits become alternative fueling & diesel being cheaper in most states..They call the Om617 a million mile motor. And I believe theres threads floating around where people have posted pictures of 900K

For me, I'd love to do the swap, it would better fit my expo rig & make it more appocalyse friendly...think bio-fuels!
But the 4.0 will go 500K, it will degrade & loose performance at that mileage, more so than a diesel would. In my case I would gain maybe 5mpg or so over the gas motor. Diesel is about the same & often more than gas in California. And it would cost me more to get a setup going to produce Bio-fuel. So I would probably be loosing in the end!
I choose to build a 4.2L high compression, high efficiency motor...I'm using the old 3.8L crank, will have a .0038" quench height, 9.8:1 comp, ported head, stock 87-95 single pattern cam advanced a few degrees to make it come alive sooner.

Its installed -8 degrees, or 8 degrees retarded. It comes alive around 2500rpm & holds power to around 6200rpm before it falls off. Advancing the cam to say -4 would make it come alive around 2000rpm hopefully & fall off around 5500rpm. We only rev to 5300rpm max, so it makes perfect since to do so
The 96-01 guys got the dual pattern cam, it comes on really strong from 1000-4000rpm..then falls flat around 4400rpm. I prefer the 87-95 cam that stays strong to 6200rpm because it can be advanced & you get the best of both worlds..redline power & low end torque!


Currently with a 2.5" OME lift, around 3" actual, 31's AT's & 3.55 gears with a ax15/np231. I'm cruising around 1950rpm at 65mph. 242k original motor, a few mods to help mileage & I'm getting 18mpg city & 22-24mpg city. I coast, watch lights ahead of me to catch them on green & draft when safely possible! So I wouldn't gain much!

Originally Posted by zeeman

I would be curious to know what it is going to cost you to upgrade the 4.2
And what kind of MPG your going to get with it. One thing you have to consider is when the max torque curve comes in, the 4.0 it is 4000 RPM the 617 is 2400 RPM a much more usable torque curve offroad.
The 617 is also non electronic as compaired to the 4.0. Need to compare apples to apples.

Originally Posted by whiteXj2

No I know theres benefits & such, I'm saying that anyone looking at swapping should consider their options.
So far I have a ported 7120 cast head (self ported), ls1 intake valves/ls6 exhaust valves & springs, retainers ect. Intake valves turned from 2.00" down to 1.94". I have around 375 in the head. I picked the valves up super cheap though. Porting kit was 70, machine work was 218 & change. Block, I have a 3.8L crank. Can get these for around 200 with bearings to your door. I payed 168, had it & the rods/pistons rebalanced together! Rods were self polished, ARP bolts, and Kb Silovlite coated 2229 pistons. Complete gasket kit added..I'm in it around 1200 all together so far. And I don't have anything left to buy, just get off my **** and put it together lol. I'm running a mopar head gasket, .043" thick.

Quench height is .039, pistons are .004 above deck, bottom end weights 4lbs less than stock...not much but should help out cause I run my 88 to 5500rpm often. I'm getting 22mpg highway at 65mph now & 24mpg if I can draft & I have 242k & been hyrdo-locked once.. I don't expect to gain much but idk..this motor should be much more efficient.
The head got a lot of work to help flow, & such..unshrouded valves, polished chambers & exhaust runners ect ect. I'm thinking I may gain a few points in mileage...but honestly it wasn't the point of the rebuild. I only did the 4.2L mini stroker, because to get my crank turned & polished was 150, a rebuilt 3.8L crank cost 168 & would get me a zero deck height, give or take...so honestly I only did it because it cost pennys more than rebuilding a 4.0 back to stock

I don't think 24-25mpg on its own will be out of the picture though, when drafting maybe as high as 28mpg. Then again it could be a totel flop and get worse...I think I did a great job adding to its efficiency while gaining performance. Its all in how you drive it I think...22mpg on a 3" lift & 31's is great as is & yup speedos correct, I actually use my gps for speed & distance traveled & its all hand calculated!

Originally Posted by getandistr

I am thinking of putting a deseil in as well. I was looking into the Cummings 4bt. What made you choose the mercedes 3.0 Turbo Diesel engine?

Originally Posted by zeeman

This build is geared to be a high MPG alternative fuel expedition vehicle. No electronics.
Standard features will be:

Mercedes diesel conversion ( will run on Diesel, Biodiesel, WVO)
WVO conversion
4wheel disc brakes
Heavy duty D spoke wheels
Goodyear wrangler tires
150 amp alternator
110 volt inverter
Sony Am-FM- SW radio
CB radio
Custom front and rear bumpers ( air tanks)
Front winch
Skip plates
1 1/4" heavy wall tube roof rack
Solar panels on roof rack (alternative power)
Off road lites on roof rack
Fresh water tank.
Capable of towing a camp trailer

This is a prototype for a possible production run based on a 89-2001 Jeep Cherokee refurbished.

Originally Posted by outlawtr450

sounds like a bugout rig!!!

Originally Posted by poorstang

Where did I get the crank?

Originally Posted by zeeman

The 4bt is way to heavy for the Cherokee, and they are expensive to buy. I went with the 99 606 3.0 in this one because I already had the engine and this one is being built for myself. The future builds will have the early 617 3.0 5 cyc. engine which are available resonable and fit well in the engine compartment.

Originally Posted by getandistr

I've looked it over and I really like the 617. Any good places to actually find one without buying the whole car? The cummins 4bt can be found anywhere that's one of the other reasons I liked it.

Originally Posted by nowhres

The early 617 3.0 engines, are there years that are better than others? What, if any is the best year to look for?