Diesel Swapping FJ40

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I’m my 1979 fj40 rebuild, I’m considering all options before starting to put things back together. I know fuel mileage isn’t the focus with these trucks but it makes my wallet flat just imagining the worst case scenario of getting 10-12 mpg from my 2f engine 😬
I don’t think quite have the budget for a Toyota diesel since options that would make this build great (like the B or 2b) go for a pretty penny. I am straying from stock and considering something like an Isuzu engine or something with efficiency more in mind. I’m not as worried about power as much as some peopleand I’m just aiming to save constant trips to the gas station. Any thoughts on this? Do I need to worry about rpm ranges with a 4 speed and 4.11 gears? Thanks!
 
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I know a little about a lot of things, so I’ll give you what I can.
Diesels do like to stay in the lower RPM range, however, if this is just an around town rig, you’d probably be okay with the 4.11 gears.

There are many diesel swap options. You mention efficiency, VW diesel swaps have been done.

You’d really need to do your research to find what you’re looking for in a swap. Many years ago I was going to put a GM 6.2L in my 40, but I liked the Suburban I bought to rob the drivetrain from too much. I was going with the 6.2L because I knew those engines and knew what I would get out of it.
 

pb4ugo

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You need to figure the cost of the conversion and engine and the added mpgs you'll gain compared to doing nothing. Youll prabably find youll have to drive it forever to recover the cost. You need to be honest with yourself and look at reality. Usually better mpgs are just an excuse for a new power plant. Its probably better to just swap in a pair of 3.70 3rd members to get a slight increase in mpgs. In a conversion you figure the cost of the engine and add a couple of grand in other big stuff, then it will nickel and dime you to death on little stuff, till your done.
 
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Some people have been doing Cummins swaps recently. Not exactly sure how much they cost though but it’s becoming more and more popular to put in a Cummins R2.8

Guy in this post says he's paying 33k for a shop to do it. Adding power steering at the same time but still

 
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Pretty much what PB said, but here's my .02 if you stick with diesel. I have done 3 swaps with the little known cummins 6AT. Same physical size as 2F or GM 235 series six. All 3 of mine had chev bellhousing/clutch etc. 210 cu in (3.4 L) , 120 hp. It's an IDI so designed to rev. This engine designed by cummins for onan gensets originally. I have a 33 page treatise by the SAE describing the development of this engine and they ran test engines at 3600 rpm for 10,000 hours without any major failures. In the mid-late 80s they started automotive and marine versions. All of mine came from UPS trucks. They ran them a couple of years and the drivers revolted because of sitting alongside them with the noise. UPS sold them in lots of ten, and they still exist. Parts come from Onan or Cummins. Bosch pump, Various turbos used. Mine have been reliable/bulletproof and sip fuel. 2 came from Seattle area for 1000.00 each other came from Texas and 400.00 shipping on 'we ship engines.com.' GM granny low SM 465 is a bolt on or Toyota with Chev kit. Oh, and mine have been swapped into old American pickups, but a Guy named 'Royal Rose' online had great sucess into a 55. Search on youtube , I have a few videos as Gary Mt.Pickett.

Old Pops cranks his winch.JPG
 

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I’m my 1979 fj40 rebuild, I’m considering all options before starting to put things back together. I know fuel mileage isn’t the focus with these trucks but it makes my wallet flat just imagining the worst case scenario of getting 10-12 mpg from my 2f engine 😬

I love a diesel for the low-end torque, but if you're doing this swap just for the mileage, I doubt you will ever get your money back. Most folks just don't drive a 40 that much; you may be the exception. I drive mine most days, but still don't manage to put a ton of miles on it. YMMV
 
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Do a diesel swap because diesels are cool. Don’t do a diesel swap because of practicability. In almost every single case, even new vehicles, you will only make your money back on fuel if you drive it like 50,000 miles a year or something
Yeah, but there's also something psychological that I can't ignore where at 10 mpg, I didn't ever want to drive an SBC FJ40, but at 22 mpg the diesel FJ40 is now my favorite thing in the world.
Even if it takes 80,000 miles for that to pencil out, it changes the fact that now I do want to put 80,000 miles on it.
 
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I know a little about a lot of things, so I’ll give you what I can.
Diesels do like to stay in the lower RPM range, however, if this is just an around town rig, you’d probably be okay with the 4.11 gears.

There are many diesel swap options. You mention efficiency, VW diesel swaps have been done.

You’d really need to do your research to find what you’re looking for in a swap. Many years ago I was going to put a GM 6.2L in my 40, but I liked the Suburban I bought to rob the drivetrain from too much. I was going with the 6.2L because I knew those engines and knew what I would get out of it.
Okay, good to know about the vw diesels. I’ll look around at them and see what might fit what I’m looking for. I’m really not looking to do a v8 swap though cause I want to keep to the inline configuration.
Thanks!
 
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Pretty much what PB said, but here's my .02 if you stick with diesel. I have done 3 swaps with the little known cummins 6AT. Same physical size as 2F or GM 235 series six. All 3 of mine had chev bellhousing/clutch etc. 210 cu in (3.4 L) , 120 hp. It's an IDI so designed to rev. This engine designed by cummins for onan gensets originally. I have a 33 page treatise by the SAE describing the development of this engine and they ran test engines at 3600 rpm for 10,000 hours without any major failures. In the mid-late 80s they started automotive and marine versions. All of mine came from UPS trucks. They ran them a couple of years and the drivers revolted because of sitting alongside them with the noise. UPS sold them in lots of ten, and they still exist. Parts come from Onan or Cummins. Bosch pump, Various turbos used. Mine have been reliable/bulletproof and sip fuel. 2 came from Seattle area for 1000.00 each other came from Texas and 400.00 shipping on 'we ship engines.com.' GM granny low SM 465 is a bolt on or Toyota with Chev kit. Oh, and mine have been swapped into old American pickups, but a Guy named 'Royal Rose' online had great sucess into a 55. Search on youtube , I have a few videos as Gary Mt.Pickett.

View attachment 2744675
That’s sweet! Never knew they existed but I’m definitely looking up the 6at now. I’ll definitely check out your videos too. Thanks for the solid suggestion!
 
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Yeah, but there's also something psychological that I can't ignore where at 10 mpg, I didn't ever want to drive an SBC FJ40, but at 22 mpg the diesel FJ40 is now my favorite thing in the world.
Even if it takes 80,000 miles for that to pencil out, it changes the fact that now I do want to put 80,000 miles on it.
Yeah that’s exactly it. It’s not all about the long-term savings but more about wanting to drive it. It’s always going to be a second car and I don’t want to be leaving it at home all the time because it costs an arm & leg to run. Not to mention that diesel doesn't stink as bad as gassers.
 
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being from Canada, you should be looking for a 3B from a rusted out BJ60

buy the whole truck, remove 3B, H55, engine mounts, etc.
Yeah so I’ve wondered, is the 3b much better on fuel? I know the displacement is also big. I’ve never seen the stats to see if a 3b really is all that different in efficiency. An h55 would be nice to get my hands on though.. good to know that I should be looking out for a bj60. Might be expensive but I’d be willing to part out the rest of the truck to make up for it.
 

flx

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A B or 3B is a lot better on fuel but be aware, they are a lot less fun to drive than a 2F. They have a lot less torque, power, low-end torque, everything than any F engine.
It's not like driving a modern turbo-diesel.
 
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My engine conversion paid for itself after around two years in fuel savings. It took about 22,000 miles to break even.

It's simple math of you want to figure it out!

Have to say the new power train would still be worth it if there was no fuel savings. I love it.

Mike
 
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Yeah so I’ve wondered, is the 3b much better on fuel? I know the displacement is also big. I’ve never seen the stats to see if a 3b really is all that different in efficiency. An h55 would be nice to get my hands on though.. good to know that I should be looking out for a bj60. Might be expensive but I’d be willing to part out the rest of the truck to make up for it.
No joke here, I get low 20's with my non turbo 3B. It is the most economical vehicle we own. Now, as someone mentioned earlier the cost of a swap is going to take awhile to recoup your funds. There is also a cool factor to the 3B sound!!
 
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Yeah so I’ve wondered, is the 3b much better on fuel? I know the displacement is also big. I’ve never seen the stats to see if a 3b really is all that different in efficiency. An h55 would be nice to get my hands on though.. good to know that I should be looking out for a bj60. Might be expensive but I’d be willing to part out the rest of the truck to make up for it.
Pretty sure 3B is slightly worse on fuel than the standard B, but the difference is minuscule and not really important. It has about 10 extra horsepower, better parts availability and overall a stronger engine than the B. You can also turbocharge the 3B a lot easier than the B if you want to go that route. 3B with a turbo and H55 is like a dream if you want to be semi period correct.
 
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Okay yeah this probably is the best way to go. Not to mention that a Toyota-correct engine really keeps the resale value up. I’ve already found that there’s a donor bj60 listed in Quebec. Might be able to work out a private cash deal and pick it up. Having the h55 would be the cherry on top for a great diesel rig
 
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