handcannon,
ever think about doing a Marlin Crawler toybox as an adapter between the toyota t-case and the 700R4. looks like you are going to add something between 9-10" to adapt everything with the AA adapter and 203. I guess you're using the doubler to give you back some of the low end from going to the 700R4? I think the toybox is around 12" (not sure on that one) and from what I've heard its as tough as you can get for our application. The only issue is $$$. I'm not taking the "spare no expense" route on this project, but I am trying to get things the way i want them the first time. Right know my planned combo is the 6.2 (maybe with some sort of force induction) with the 700R4, 2.28 toybox, stock 16 spline t-case, 3.7 gears and 33" tall tires. With this setup I'll be able to cruise at 68 mph at 1800 rpms in overdrive and still have a crawl ratio of 50. Something to think about.
Brian,
Like most older diesel it likes its RPM low for fuel economy. Most say around 1800RPM is the sweet spot, which happens to be where this engine seems to make most of it torque. This might vary a bit depending on mods. As for MAX RPM, I think it 4500RPM but I would have to check to make sure about that one
I've wondered about a 6.2 since it is a near direct physical swap with a 350.
But what this tells me is that it is a poor idea without an overdrive, and even then it still may not work out.
My FJ40 needs about 3000 rpm at 60 mph. Even with a 5-speed aussie Toy tranny, that would only drop it to 2400, which is not within the optimal fuel economy range. How much of a penalty there would be, I dunno. On the other hand, if I recall right, first gear in this tranny is lower than the domestic 4-speed, so perhaps it would allow a change of gears from 4.10 to 3.73., which is a 10% change. RPM would drop from 2400 to 2160.
That puts the RPMs into the ballpark, but at what cost? First there's the engine. I have no clue what a decent runner would cost, nor what it would cost to rebuild one. Anyone?
Then there are the peripheral parts, like flywheels, clutch, wiring mods, etc. Maybe budget $300 for this?
The aussie 5-speed is $2500 for a runner, and $3000 and up for a rebuilt, not counting shipping.
The gears possibly could be swapped straight across with someone who wants 4.10s, as they are more desirable than the 3.73s, so I'll chalk this one up as needing nothing more than gaskets and fluid.
I'm guessing this conversion would exceed $3500 at a minimum, and could easily go another $1000 on top of that.
Benefits would be a doubling of the fuel economy, from 9 to 10 mpg to 20 to 21 mpg. (Which brings up another question - does the 6.5 with turbo get better fuel economy?)
On the other hand, diesel costs more than gas. Right now, locally, diesel is only 10 to 20 cents more a gallon. But it has gone as much as $1 to $1.50 more per gallon.
Biodiesel. More and more we're seeing local demands for biodiesel blends. Ford will not warranty their engines with more than a 5% mix. How does the 6.2 like biodiesel?
Driveability. My 350 is quite streetable, with the proper carb (Quadrajet). It was miserable with a Holley. It lugs almost as good as a six-banger with the Quadrajet, but could not lug whatsoever with the Holley. It also can accelerate decently when it needs to. The diesel has outstanding low end torque, but would otherwise be sluggish, especially around town. The diesel would also be immune to steep grades and slopes, though some carbs do a fairly good job with this.
Because of the costs of conversion, the diesel would have to be compared to installing fuel injection on a 350. The two route are to just drop on an Edlebrock on the stock carbed 350, or put on a factory EFI unit with heads designed for it. I'm told this can get the fuel economy of the FJ40 with 4.10 gears into the 14 to 15 mpg range. Comments?
Doing the math, if the fuel savings for a diesel vs carbed gas is about half, that means the payoff for $3500 minimum in conversion costs would be, of course, $3500 in fuel. I'm only putting about 1500 miles per year on my FJ40 at most. At 10 mpg, that 150 gallons. Multiply that by, say, $3.00 a gallon (prices will probably go up during the payoff period) and that's $450 in fuel. Saving half of that by going diesel would be $225.
So in my situation, $3500 to convert (and we need to more accurately define this figure) divided by $225 per year in savings means it would take 15 years to pay off the investment.
Obviously a daily driver would pay off sooner. And if the conversion cost more it would push it off later.
Now in my case, I'd be swapping out a perfectly good 350, which could be sold. But I can see this swap being more justifiable for someone with a dead motor, or even a project FJ40 with no engine at all. That's where it starts to look attractive because you have the cost of the engine on both sides of the ledger sheet.
