And you guys hate a SBC under the hood...(Isuzu Diesel Swap)

[JeepinPete]

How would a rice burner float your boat

As I mentioned in another thread, I am pulling the 5.3L out of the Cherokee. As if a Chevy wasn't bad enough, I'm going way out there, and swapping a, wait for it...an Isuzu engine To be specific, a 4BD1T, or in layman's terms, a 3.9L 4 cylinder diesel out of a NPR box truck OK, not really rice, but definitely foreign.

The 4BD1T is basically a direct competitor to the Cummins 4BT. 140ho, 243ftlb torque. Supposedly a smoother, slight more efficient engine. They are a somewhat popular swap in the Toyota Land Cruiser community. Anywhere from 24-28mpg in a rig similar in size to our own.

Why would I take out a perfectly good 5.3 and put this engine in its place? Primarily fuel economy and low end torque. The Gen III engines are wonderful, and like to rev. (I drive a '06 GTO with a LS2 most days, and oh what fun that is .) But with the 5 speed, creeping around offroad isn't playing to its strength. And my intention once the dust settles is to use my Cherokee as my daily driver, and part with my GTO. I drive 40k miles every year, so a 50-75% improvement in economy is easily justified.

Compared to the 5.3, this is an all mechanical swap. Even the fuel cutoff is mechanical. I doubt it will take more than an evening to take care of the wiring.

As far as the rest of the drive train, I am keeping the NV3500 and NP241C. I have a range box built from a NP241 that I will also add. Since the 4BD1T was never attached to a GM tranny, I will have to build an adapter plate. I've put a lot of time into the design of the plate, and have started the machine work. With any luck, it will be done this week. Then the fun begins

One thing that I do worry about in all this the gears in the rears. I swapped out the 3.54 for 4.56's. I suspect the cruising rpms are going to be high, so I may have to swap the 3.54 back in. Time will tell on that one.

[rustywagoneers_com]

One of the engines I am watching for for my tow rig.

[dusty]

now just plan on going out for oriental food more often and ask for the excess oil after dinner so you can drive home

welcome to the dark side i've been following your tech on the 4bt page

good luck.

FYI i bypassed my intercooler first couple of days out than hooked it back up after dealing with the AC. large difference in EGT's and a 2-3 mpg difference in highway fuel consumption. so id say take a serious look at doing the 90-93 dodge inter cooler like i did on mine.

with 35's i found i really liked 3.73's with a larger tow rig 6bta and a 6spd nv5600 (same OD ratio as the nv4500) but that a 6bta and 3.54's with 35's was also a good cruising combo. on the bottom end of the rpm range i want when towing since at 60-65 mph i am at 1600-1700 rpm in OD and in ca we are regulated to 55 mph towing so you can see the lugging issue. but i like it because i could use i could use direct into the 60 mph range with a trailer and i had good mid gear splits, with a 5 spd the 3.54's were really a saving grace third gear was tached out way too easily when towing ect.......i alternated between 315/75 r16's and the 285/75r16's with 3.54's and it was really a tough call the 6spd really makes things easier by splitting 3rd for you.
with the 4bt my 3.54's and 33's, nv4500 is spot on for 65-70 mph cruising at 1800 rpm-1900 rpm, little less off the line torque than my 6bta so the smaller tires compliment that well. with 3.54's and the 33's third gear is a little bit of a stretch without govenor springs which i will be adding soon. the split from 3rd to fourth is a PITA at around 40-45 mph i am tached pulling 2700 rpm and then when i hit fourth i am back down to 1700 rpm and you usually loose a litte speed so its more like 1600. a close ratio 5 spd would be nice or the gear split of the nv5600 would be better but gov springs is an acceptable compromise. if anything and due to the fact you have the LSD's front and rear maybe 3.92s would get you in there rpm wise 3.92s would at 65 mph give you around 1800-1850 rpm which would be pretty darned close to the sweet spot of 1750 in od and you should be able to use those LSD cases still since the dana 44 case split is between 3.73/3.92.


wiring is simple. with your ability you'll be up in a week or so depending on time available

if you need to address the clutch issue contact peter at south bend he can make up a hub/disc/pressure plate combo in a pretty compact package that can take the low end torque of a diesel quite well. better than a gas disk and hub will. food for thought but after ripping the hub out of a few diesel conversions i found i no longer trust out of the box clutch combos shoot even the old 4bt's married to np435's and t19's had issues with inputs and hubs over long periods of time. food for thought in your quest

[JeepinPete]

Good to know on the intercooler. I've been debating on whether to add one or not.

How do you like the gearing (3.54 w/OD)?

[dusty]

ha you were typing while i was. lol

see above for some mid day burned out gibberish.

any questions about my issues dont hesitate to call or pm. glad to dig up any info for you but i doubt you'll need much knowing what you know.

[The PIG Smith]

NOT a foreign/ricer engine...well sorta

As you are well aware of, the 4BD1T is an Isuzu engine.
The Chevy Duramax is also an Isuzu engine.
As GM has a large interest in Isuzu (do they outright own Isuzu? part owners? controlling interest?) then I would consider the 4BD1T a quasi domestic engine.

I've been told that Isuzu makes more Diesel engines than any other brand.
I dunno how true that it...

While I think the NV3500 will a great tranny behind your 4BD1T.
Do these engines come with an SAE #2 bellhousing?
If so, this would open the door to a whole host of industrial transmissions, like a Fuller Roadranger for example.

I am want to wish you the best and thank you for blazing new trails for us.

[DieselSJ]

Welcome to the dark side.

I'm looking forward to watching the progress on this.

[mattmopar440]

Thank God some common sense in you chevy boys
Now what are chances we can Get Old Al to change his mind

[Headhoncho]

Pete, when you're done dropping the deisel in yours, you can drop one in mine too.



JR

[JeepinPete]

There is a SAE #3 clutch housing available for it, but they are rare.

I am curious how the NV3500 will hold up. It has a bad rap, but it was rated for 300 ft lbs torque at 8k lbs GVW. That in my book is pretty stout for a 4500lb Jeep. I do not drive the Cherokee in an abusive manner on road or off, so I think it will do fine for me. Plus it has better gear ratios than a NV4500 or any of the granny boxes.

The problem with 3.92 gear is I am running a hi pinion Ford D44 up front. 3.92 doesn't seem to be available for that axle. I have 3.54 for both the front and rear, and I am sure I can swap the limited slips with someone for the taller ratio case. Regardless, I will be running it with 4.56's off the bat and go from there.

As for the clutch, first attempt is going to be a late model GM truck clutch from a 4.8L. It has a double sprung hub, which I am hoping will smooth out the torque spikes of the engine. If I destroy the clutch hub, the tranny probably isn't going to last long either.

[JeepinPete]

You know JR, last years ECI is what got me thinking about this in the first place. Though I managed 18 mpg on the trip down, it still was an expensive trip in fuel. I know you were hurting worse than Ann or I in that department. There are a lot of road trips that I want to take in the future, like heading out west to run the Rubicon, or Moab, etc.

[Headhoncho]

You know JR, last years ECI is what got me thinking about this in the first place. Though I managed 18 mpg on the trip down, it still was an expensive trip in fuel. I know you were hurting worse than Ann or I in that department. There are a lot of road trips that I want to take in the future, like heading out west to run the Rubicon, or Moab, etc.

I hear ya. I averaged 10 mpg in mine which cost me a small fortune. I just hope gas doesn't spike by this years trip. A diesel would sound pretty cool in my truck. I can't hear the radio anyway.



JR

[JeepinPete]

Ok, on to some tech. The Isuzu uses a clutch housing and a bell housing. The bell housing is much shallower than what we are used to. The clutch housing looks alot like a bellhousing bolted backwards to the engine. Anyway, I am making an adapter plate that bolts to the clutch housing, and will mimic the back of a SBC so that my Chevy tranny can bolt up to it. The Isuzu flywheel will be used fo nothing more than the ring gear, so that the Isuzu starter can be used. A crank spacer will be bolted to the flywheel, and a SBC flywheel will be bolted to it. Here are some Pro-E images:







In these pictures, the orange piece is the adapter plate. The grey disc is the SBC flywheel, and the smaller green hub is the crank spacer.

I've pretty much finished up the adapter plate. The first order of business was turning the index to the clutch housing. Unfortunately I do not have access to a large enough lathe, so I had to do this on the Bridgeport. Even at that, the Bridgeport didn't have enough Y travel to make use of the CNC control. So I set up the rotary table, and went to town.



I also didn't have a large enough caliper to actually measure what I was machining. Most of the work I do is less than .1" in diameter So I measured with a stick rule, and roughed in the index at half total depth. Then I stepped the X axis in .010" at a time until the clutch housing slipped over. I proceeded to mill the step to final depth, and set the final X .005 less. The result is a nice tight slip fit with no discernible play.



That work was done two weeks ago. I got the bolt holes drilled last Wed.



The flywheel will need some modification, basically redrilling the for the Isuzu crank pattern. Here is a drawing of a 6.0L/4L80E flexplate showing the modification needed:



I had to make minor design change for the crank spacer. I had planned on using long socket head cap screws to bolt the crankshaft extension in place. Unfortunately, Isuzu used a difficult to source thread, M14 x 1.5 to be precise. The only way I could source the bolts was to have them custom made at $30 a piece. Needless to say, I am not taking that approach.

Anyway, the crankshaft extension is now a two piece affair. The green piece will be steel, drilled with clearance holes for the Isuzu crank bolts, and drilled and tapped for the GM flywheel pattern. I can source hex head bolts in the proper thread for the Isuzu, so I will counterbore the back side of the blue piece to clear the heads. If I tried to do this as a one piece affair, the counterbore necessary to clear the hex head would cut through the index for the GM flywheel, which simple won't work.





I started the crankshaft extensions today at lunch. I am hoping to get them done by then end of the week.

[dusty]

You know JR, last years ECI is what got me thinking about this in the first place. Though I managed 18 mpg on the trip down, it still was an expensive trip in fuel. I know you were hurting worse than Ann or I in that department. There are a lot of road trips that I want to take in the future, like heading out west to run the Rubicon, or Moab, etc.

you make that trip i'll show up. rubicon is only 3 hours give or take a little. too bad PA isnt closer i stumbled into another 4bt for next to nothing and it probably would have made your life a little easier...and been passed on for the same song i paid since its going in a chief


tell ya the truth if i hadn't had the nv4500 already i probably would have opted for the ford sb zf 5 spd and used the ford adapter.

since you have a 79 the driver side exhaust will be nice you will have better room at your t-case to frame area than i do. then you cna cross over mid ship behind the t-case.


last years fuel prices were what pushed me over the edge. i couldnt jsutify a 10:1 401 with big cam for putting around and my dodge diesel was racking up miles at a rediculus rate wearing out a good tow rig for highway trips. 8-10 mpg vs 25-28 mpg hard to argue.

[HI-TECH REDNECK]

i have to ask, how much time have u put into those Pro E models? more importantly, how much time have you spent taking measurements off of the actual parts in order to draw up those models?

from my experience so far whenever i do that i find i have quite a bit of time invested in pulling measurements, thinking it all over, drawing it up in Solid Works, thinking and tweaking some more, etc....

nice job tho this is an interesting project. i like your use of Pro E also, great tool!!