The mileage project

[Gordon Maney]

Given all that we know about fuel prices and our inevitable future, it seems that a diesel powered Dodge would make a lot of sense.

Also, considering purchase price for a base truck, replacement parts and sheetmetal availability, it seems that the M37 would be the obvious choice. Maybe some here disagree on that; feel free to comment.

If a person wanted a truck that got the best possible fuel economy, with the most modest build price, how would this project be done? I am imagining this being an owner-built project. Can this truck be made to have acceptable operating noise levels?

Can we have a thread here that constitutes inspiration, rather than fantasy?

What kind of mileage would be realistically attainable?

Discuss....

[mcinfantry]

mpg? i think 25 to 30 is attainable. the only issue i see is initial cost.

im working on sound deadening on the wc-53 as we speak. so i dont have that 100% solved yet.

[HWooldridge]

The complete conversion that Charles Talbert offers seems to be a good combination of features. Of course, doing it yourself would be cheaper from a labor perspective but the items he adds/changes are the right choices - so the 4BT replacement, OD trans and 4.89 gears are the first things that come to my mind for a daily driver in most parts of the country.

For the past 10 years, I have lived on a farm-to-market road where I could drive to work at 45 mph the whole way so I'd be happy with a fresh, stock 230 and 4.89's but I can get by with the stock axles. One of these days, I'll rebuild the engine properly - the previous owner did a poor job and it shows.

I think good diesel sound deadening can be added to the underside of the cab and the firewall. You could also go inside the doors and glue something to the outer skins. The M37 will never be dead quiet because of the soft top but I believe it could be dampened a lot. It might also help to run the exhaust up the side similar to a fording kit so some of the exhaust noise goes upward.

I also think a later Dodge like a W300 would be a good choice - provides a more civilian perspective to begin with.

[Gordon Maney]

The complete conversion that Charles Talbert offers seems to be a good combination of features. Of course, doing it yourself would be cheaper from a labor perspective but the items he adds/changes are the right choices - so the 4BT replacement, OD trans and 4.89 gears are the first things that come to my mind for a daily driver in most parts of the country.

For the past 10 years, I have lived on a farm-to-market road where I could drive to work at 45 mph the whole way so I'd be happy with a fresh, stock 230 and 4.89's but I can get by with the stock axles. One of these days, I'll rebuild the engine properly - the previous owner did a poor job and it shows.

I think good diesel sound deadening can be added to the underside of the cab and the firewall. You could also go inside the doors and glue something to the outer skins. The M37 will never be dead quiet because of the soft top but I believe it could be dampened a lot. It might also help to run the exhaust up the side similar to a fording kit so some of the exhaust noise goes upward.

I also think a later Dodge like a W300 would be a good choice - provides a more civilian perspective to begin with.

Would you still use the 4BT in the W300?

[mcinfantry]

i never tried to get more hp/tq from mine in my 5/4 m715. it hauled all i could ask in the bed, and never had a problem with it. i tried to flat tow another m715 and wasnt happy with it (never pulled the d-shafts or even checked the brakes). i never tried to find out where the problem was. i ended up selling the 715 before i ever pulled anything else.

i would say 4bt would be good for any 1/2 ton to 1 ton with carried loads, and towing <6000 range. now i will add that iirc, 16000gvwr was for a cpl858 4bt

im runnig 4.88 gears in the wc, but it isnt on the road just yet. ill be able to compare it to a chevy blazer with slightly better than stock sound deadening(and a 4bt)

[Ugg013]

Hi Gordon:

GL always offers the 6.2 GM diesels in crates. What condition they are is unknown. Will they fit in a M37/PW/WC? Unkown. Just another direction to look. Diesels are the future. I'm tryin to convince the wife now. her little truck crossed the 150K mark, and that's mostly heavy traffic mileage. Like most, when she thinks diesel, she thinks of the big rigs and the smell & noise. Our deuce is no help with that thought, but it doesn't even have a muffler. HA!

So Gordon, is this busy work to keep ya occupied during the interim? Charles Talbert has already done extensive research/work in this direction as ya already probably know, and Charles IS known for his quality work/knowledge. I believe he already has much info about this at his site, so he'd be the Go To guy for info (that's not meaning to dismiss anybody elses imput).

Later
Ugg

[MoparNorm]

Ugg those 6.2's are in crates for a reason, but they really should be in landfills........
The 4bt is adequate, but for practical reasons I'd want a ISB version, much smoother and very quiet compared to the earlier versions.
Gordon certainly didn't mean to discount Charles' work, just to explore new possibilties. Charles work is top notch and if there becomes a new technology or motor option, he'd still be the one in my book, to perform the work.
The 2.8 Detroit Diesel gets 34 mpg in vehicles under 5,000 lbs, with gearing in the 4:10 range.
The new Cummins 4.0 will get better than that and as a V-6 it will fit in applications where even the 4bt is too long, but it may be too wide for older Dodge Military rigs. I do not have size specs on it yet.

A late 90's to pre IFS axle Dakota may be a candidate for a small diesel, but limiting choices to Dodges is narrowed by the poor current crop of Dodge offerings.

When it comes to a tad more creature comfort than the M37 affords, the Sweptline, Power Giant and Town Wagon line offers a few trucks with potential for a "modern" street ride while still maintaining a rugged capability off road. There are several trucks running 6bts but the weight of the 6bt makes that choice borderline. I'd love to see one of those trucks mentioned, with the new Cummins 4.0, quiet, powerful, great fuel economy, I have no idea what is involved however to maintain the new fuel/engine management systems without all the sensors and toys that come with the computer controls.

[mcinfantry]

the 4.5l 4cyl is computer controlled. keep that in mind.

[MoparNorm]

... Diesels are the future. I'm tryin to convince the wife now. her little truck crossed the 150K mark, and that's mostly heavy traffic mileage. Like most, when she thinks diesel, she thinks of the big rigs and the smell & noise. Our deuce is no help with that thought, but it doesn't even have a muffler. HA!
Later
Ugg

Ugg, just set it up to have her stand next to a VW TDI, Chevy or GMC Duramax, Jeep Liberty CRD or Grand Cherokee CRD with the Bluetec diesel. But don't tell her it's a diesel until she says "it's nice" then spring it on her that it's a diesel and it gets mpg in the 30's.....= )

[HWooldridge]

Would you still use the 4BT in the W300?

I believe so - it might take some grey matter to work out final drive ratios but the engine should be a good match. Do you think it's too small?

[MoparNorm]

Yes.
It might move it OK on the road, the motor is rated at over the GVW of the 300, but it'd be marginal in certain off-road conditions.
However I could be persuaded otherwise....= )

[mcinfantry]

i completely disagree. it will be more than adequate offroad, it may be lacking on-road towing under certain conditions.

[MoparNorm]

I suppose one man's definition of off-road is different than another man's. From what I've seen of the 4BT it's adequate on the hi-way, except maybe under a load on a long grade?
But the off-roading that I do requires a LOT more torque than the 4BT can dish out to move a 6,000+ lb vehicle.
It's great for 1/2 and 3/4 ton rigs and maybe a 1 ton dirt road runner, but I'd need to see one in action before I agree.
I'd like to see a little more torque out of it before it went behind a 1 ton. Are there hop up parts for it and will the motor live with them?
http://photos.imageevent.com/moparnorm/jeeps/websize/currieside.jpg

[mcinfantry]

a 4bt puts out 200ftlbs of tq at 1000rpm. name any gas motor anywhere that produces a useable 200ftlbs at 1000.

i again refer anyone to this video where i was over 7000lbs wet weight. this is second gear, low range. nv4500, np205 and 4.56 gears pushing 38.5" tires.

http://homepage.mac.com/ltalessi/iMovieTheater124.html

non-quicktime
http://www.youtube.com/watch?v=V3vL9RGJ3ek

what do you see as missing, or where do you see the power level lacking?

i once tried to uproot some shrubs and had the 715 on pavement in 1st, low range, front and rear axles locked and i was on dry asphalt and could spin all four tires almost at idle. and i wasnt riding the clutch.


iirc curb weight was 6300lbs on the 715. thats 1-ton to me.

ive never heard of anyone, anywhere looking for off-road performance increases. its always been on-road specific power increases.

give me a for instance for the certain offroad conditions you mention, and ill try and see if i ever experianced any similar ones.

[MoparNorm]

That's pretty cool!
A stock 4.2 in line six Jeep puts out 240 lbs of torque @ 3,000 rpm, 205 off idle. Mine puts out 350 lbs @ 2500 rpm, 250 off idle, that's so so for a Jeep CJ, I'd like more for a 1 ton.
Funny that you posted ... "ive never heard of anyone, anywhere looking for off-road performance increases. its always been on-road specific power increases."
You need to come on out to SoCal and see what we do out here, it's all about off-road performance, on road performance from non-diesels is pretty much illegal. We're looking for low rpm grunt, even with the CJ's. I suppose it's same with the boys from Texas, Colorado and New Mexico. In Moab, they're putting up some pretty big numbers, but they are doing it with gassers. In our western rocks you need to putt at low rpm and still move over obstacles. 1 mph is sometimes too fast, but we still need torque.
Not much mud out here and too much work to clean up properly, but it is fun.....
Have pictures of the install in the 715?

[mcinfantry]

That's pretty cool!
A stock 4.2 in line six Jeep puts out 240 lbs of torque. Mine puts out 350 lbs, I'd like more.
Funny that you posted ... "ive never heard of anyone, anywhere looking for off-road performance increases. its always been on-road specific power increases."
You need to come on out to SoCal and see what we do out here, it's all about off-road performance, low rpm grunt, even with the CJ's. I suppose it's same with the boys from Texas, Colorado and New Mexico. In Moab, they're putting up some pretty big numbers, but they are doing it with gassers. In our western rocks you need to putt at low rpm and still move over obstacles. 1 mph is sometimes too fast, but we still need torque.
Not much mud out here and too much work to clean up properly, but it is fun.....
Have pictures of the install in the 715?

i do. i also have plenty from the wc53( a better install, imo)

i said no one with a 4bt has ever talked of offroad power increases.

and neither the jeep 4.2 or any chevrolet 350 puts out 200 ft lbs of tq at 1000 rpm. none. a 4bt produce useable tq off-idle. the above video was initially attempted in 3rd, low range. when the engine stalled, i tried in second and made history. please not, i was NOT feathering the clutch. when the strap tightened i was 100% off the clutch

show me the dyno chart from one.

[MoparNorm]

That's pretty cool!
A stock 4.2 in line six Jeep puts out 240 lbs of torque @ 3,000 rpm, 205 off idle. Mine puts out 350 lbs @ 2500 rpm, 250 off idle, that's so so for a Jeep CJ, I'd like more for a 1 ton.
Funny that you posted ... "ive never heard of anyone, anywhere looking for off-road performance increases. its always been on-road specific power increases."
You need to come on out to SoCal and see what we do out here, it's all about off-road performance, on road performance from non-diesels is pretty much illegal. We're looking for low rpm grunt, even with the CJ's. I suppose it's same with the boys from Texas, Colorado and New Mexico. In Moab, they're putting up some pretty big numbers, but they are doing it with gassers. In our western rocks you need to putt at low rpm and still move over obstacles. 1 mph is sometimes too fast, but we still need torque.
Not much mud out here and too much work to clean up properly, but it is fun.....
Have pictures of the install in the 715?

Ha!Ha! That's your suspicious Cop nature...= )
I don't have a chart or print out of my 4.2, but here is a 4.0 chart (which has less torque than the 4.2)
http://photos.imageevent.com/moparnorm/jeeps/tcurve.gif


Post some pictures or email then to me, I'd like to see the fit and clearance, I have a Grand Wagoner that I was looking for a diesel to install, same firewall sheet metal and engine bay dimensions as the M715.

[mcinfantry]

Ha!Ha! That's your suspicious Cop nature...= )
I don't have a chart or print out of my 4.2, but here is a 4.0 chart (which has less torque than the 4.2)
http://photos.imageevent.com/moparnorm/jeeps/tcurve.gif


Post some pictures or email then to me, I'd like to see the fit and clearance, I have a Grand Wagoner that I was looking for a diesel to install, same firewall sheet metal and engine bay dimensions as the M715.

ok, ill try and dig some up. its a REAL easy fit in a waggy.

i see your dyno chart , but it isnt useable.

you can get in a 4bt truck, dump the clutch and it WONT stall. i may be headed out your way later this summer, or if you get anywhere near me, you are welcome to drive it.

[MoparNorm]

ok, ill try and dig some up. its a REAL easy fit in a waggy.

i see your dyno chart , but it isnt useable.

you can get in a 4bt truck, dump the clutch and it WONT stall. i may be headed out your way later this summer, or if you get anywhere near me, you are welcome to drive it.

The dyno shows 200 ft lbs at 1,000, for the stock 4.0. My 4.2 torquer can idle up a 15% slope with me walking beside it, but it's not enough motor for a 1 ton.
I'd love to see and drive your rig, it looks sweet! Maybe we could meet at Jim's and you can see his 4bt Townie at the same time.
Thanks!

[JimmieD]

I have to agree with McInfantry on this. I have zero diesel experience before my conversion so I was utterly amazed at the result. Even with truck very heavily loaded, pulling another truck very heavily loaded, just ease out the clutch, no throttle, in 2nd gear to start!

Towed my Chevy Luv down here with the Townie. Townie was full to the roof with all I could cram in, including the floor covered with scrap steel, boxes of tools, heavy truck parts etc. and LUV was full of scrap metal, parts and misc. Can't know for sure, but Townie at least 2,000 in the back, Luv at least 1,250. Townie weighs 2.6 ton empty. I could feel the strain but made every hill with ease, no problems at all. Only thing that limited speeds was LUV wanting to hula on the towbar. Averaged over 19.5 mpg for 600 miles! Have never needed 1st gear [4.1 final with 29" tires] except coming up the steep and rutted driveway with this load.

If EVERYTHING went right a SKILLED fabricator with good tools could do the swap for $4,000. 'Million Mile Motor' and a premium drivetrain like NV4500 and Dana 60 axles, heavy-duty components and you're good for the duration. At 30+ mpg and extremely low maintenance it doesn't get any better, and no electronics but 1 wire for fuel solenoid.

[mcinfantry]

i think it could be done for 4000. your right, its has to line up, but possible

[Gordon Maney]

I have to agree with McInfantry on this. I have zero diesel experience before my conversion so I was utterly amazed at the result. Even with truck very heavily loaded, pulling another truck very heavily loaded, just ease out the clutch, no throttle, in 2nd gear to start!

Towed my Chevy Luv down here with the Townie. Townie was full to the roof with all I could cram in, including the floor covered with scrap steel, boxes of tools, heavy truck parts etc. and LUV was full of scrap metal, parts and misc. Can't know for sure, but Townie at least 2,000 in the back, Luv at least 1,250. Townie weighs 2.6 ton empty. I could feel the strain but made every hill with ease, no problems at all. Only thing that limited speeds was LUV wanting to hula on the towbar. Averaged over 19.5 mpg for 600 miles! Have never needed 1st gear [4.1 final with 29" tires] except coming up the steep and rutted driveway with this load.

If EVERYTHING went right a SKILLED fabricator with good tools could do the swap for $4,000. 'Million Mile Motor' and a premium drivetrain like NV4500 and Dana 60 axles, heavy-duty components and you're good for the duration. At 30+ mpg and extremely low maintenance it doesn't get any better, and no electronics but 1 wire for fuel solenoid.

I may have missed something in this thread, but where did you get the 30+ miles per gallon figure?

....and in this scenario, how are we sourcing the engine; the Frito truck approach?

[mcinfantry]

avg mpg, here in louisiana was 24 to 26mpg. thats city and hwy and running almost 75.

i ONCE drove from mobile al to near baton rouge slightly higher than 30mpg.

that was a used, not tuned up, 140,000+ mile frito engine.

that was in a almost 7000lb curb weight m715 with 4.56 gears, 38.6" tires and nv4500

[Gordon Maney]

avg mpg, here in louisiana was 24 to 26mpg. thats city and hwy and running almost 75.

i ONCE drove from mobile al to near baton rouge slightly higher than 30mpg.

that was a used, not tuned up, 140,000+ mile frito engine.

that was in a almost 7000lb curb weight m715 with 4.56 gears, 38.6" tires and nv4500

Wow — neat!

Thank you...

[mcinfantry]

Wow — neat!

Thank you...

i forgot to add that was 55mph on the 30mpg

[Gordon Maney]

mcinfantry, is there a thread somewhere here where you describe how you configured the M715? ....or would you comment on that in this thread, as an alternative?

Which particular 4BT did you use, what transmission, what tire size? Does the M715 have a 4.88 axle ratio, or something else?

Also, are the Frito truck sources drying up by now?

[JimmieD]

4BT performance is not lacking stock and hop-up is E-Z and cheap! Diesels want fuel and air & exhaust. Stock we see 105-120hp & 350+ ft lbs torque. EGT's as Exhaust Gas Temperatures are quick death to diesels above about 1,300* sustained. Stock 4Bt runs 750*-800* towing. More fuel = higher EGT unless more air comes in.

Bosch VE pump can be easily tweaked for more fuel: 3,200 rpm governor spring raises the power range, cost $20 and some time. Simple fuel adjustments, only adjustments, raise hp to 200, torque to 400. Add an HTT Stage II or III compressor housing and wheel to turbo for about $200-$300, more air! Add an aftercooler [about $250-$300] unless it's already aftercooled [4BTA] allows denser mixture and lowers EGT's. Add complete 4" exhaust from turbo outlet, including muffler, about $200 home built. Add water/methanol injection kit, runs from $200 for manual, $750 for full-auto, cools clyinder temps, lowers EGT's and increases power and can eliminate the need for aftercooler. Injected methanol is cehaper than diesel, and the water is free. May be used as needed, not fulltime unless desired. You can now add larger injectors because the hardware is in place to control otherwise catastrophic EGT's. Injectors run from $250 to $600.

Results: about 400 to 450 hp, 600-800 ft lbs torque, 400+ torque off idle! $675-$1,000 w/o injectors, $1,000-$1,400 with injectors. 3 times the power, 2 times the torque of a stock 1st Gen 6BT, still 'good' mileage in the 20's. Beat that?

One MUST install a Pyrometer [exhaust gas temperature sensor & gauge] about $100-$150, to monitor EGT's with high performance tweaks.

[mcinfantry]

the frito sources are not drying up, they are decreasing, but now that they are on dovebid, you are bidding nationwide. its kind of like the gov liq fiasco. the speculators/tire kickers are driving prices up, but in the same token some buy the stuff only to realize it is well past their pay grades and have to literally unload the stuff.......


there is NOT an infinite supply of the 4bt, but in the same token most of us only really need one.

next post is m715/4bt

[JimmieD]

Hey, mcinfantry, I wrote that from memory, or what's left of it :~ ). Do those numbers above sound right to you from our conversations 'elsewhere'?

[mcinfantry]

Hey, mcinfantry, I wrote that from memory, or what's left of it :~ ). Do those numbers above sound right to you from our conversations 'elsewhere'?

looks like 160 is more reasonable w/o any money. the guy running 200 has swapped turbo and a few things... i digress.

[JimmieD]

Thanks! So, "Simple fuel adjustments, only adjustments, raise hp to 200, torque to 400." should read, "...can raise hp to 160..."

[mcinfantry]

1967 m715.

i drove it stock for almost 2 years.

i read garbee's site and lou chou's info on-line.

i bought a frito truck for 700 w/ a blown clutch and sm465. i pulled the engine and tranny in one piece through the side door. i got rid of the truck for 500 complete (in one piece).

the 4bt was >140,000 miles cpl 858 which is 105hp and 265tq

i bought a dodge adapter/nv4500 and divorced 205. i couldnt get much help from the net at the time and geared the truck how i THOUGHT it should be. 4.56 gears (m1008 cucv axles). i had already been running the michelin xl's.

i ran into alot of interesting solutions based on reading, other peoples ideas/experiance and dumb luck. i had almost no diesel experiance other than a 1986 diesel jeep cherokee that was an absolute pos.



the m715 was swapped to saginaw power steering. a cummins 4bt runs the power steering pump by a gear. no belts to stretch, break or slip. i ran hydroboost brakes and a rear proportioning valve and 4 wheel discs. i also ran a hydraulic 'steering assist' ram. this made the steering light and easy.

i ran vintage air a/c with heat and defrost. i ran the ford taurus electric fan and a stock m715 radiator.

i ran the m715 w/o a lift. since it would clear 1100x16 michelins then i coudnt justify raising the cog. at the time i had never heard or seen a spring under open knuckle chevy d60. i made one.

[mcinfantry]

i ran a dodge nv4500 by removing the dodge slip yoke rear and replacing it with a GM fixed yoke to run the divorced 205.

i took the truck down to the frame. a buddy of mine started with a bare frame and 3 full days of work had it almost complete and turning the engine over.

we (i) mis-wired the fuel solenoid and we tried over an hour trying to get the thing started. i ran 12 volts to the starter and that didnt work. i was agitated and frustrated and thought the engine was turning to slow. we craked injector lines, cussed and swore. we called everyone we know that knows about diesels (3 people) and they said we werent getting fuel. i ran 24volts to the starter. the engine turned faster, but wouldnt run. after another 20 minutes or so i finally had ebough and ran 36 volts to the starter. it turned over so fast, it honestly made me nervous. after i burned one set of jumper cables up and melted the terminals off of two batteries i checked my wiring.

it fired right up!

i let it idle and it took 53 minutes at idle to reach 180 degrees. not too bad.

i then started playing with driveshaft angles. i tacked the rear spring mounts down, and tighened the ubolts. i put it in 4wd high and let the clutch out slowly. i spun the read axle up, and tore the ears off the yoke and didnt move an inch!

i replaced the yoke, tacked the rear better, and tightened the ujoints. i drove around the block!. i made another pass with a buddy to show him. we were grinning ear to ear!. i blipped the gas and spun the axle AGAIN destroying another yoke! i was no longer grinning!

put the thing together to try and get a little road time. i dont think i had it on the road more than a week when i stopped to check on a guy who had driven into a ditch. i was rear-ended by a mitsubishi montero doing 55mph. she totaled her truck. she bent one bumperette (slightly) and knocked a hole in the nv4500 5th gear cover.

i got it back together in time for land between the lakes kentucky.

[mcinfantry]

a buddy of mine and i trailered it to LBL for the m715 meet & greet. i hadnt had it on the road enough to comfortably drive it.

we had a few issues with blown steering o-rings (it was a burr on the ps box output flange)

we offroaded the thing for three days. i burned 5 gallons of diesel and the gas trucks burned 1 to 2 tanks. i ran in second low range the entire time. i never used first. i was told i was going so slow at idle i was forced to take up the rear.

the 4b was quite the hit.

my buddy, not a diesel nut, had his doubts from day one. after the ride he was so impressed he has sworn off gas motors. he is attempting to put a 4b into his blazer, but it may end up in a 86 2wd chevy 1500.

observations.

the truck ran too cool in the winter. no heat for the heater.
the truck ran too cool in the summer, and the elec fan only came on for the a/c

the truck probably could have had the engine gone through, but i never did. i never felt it needed it.

all in all you could easily find a 4bt for 2000, and a 4sp sm465 for free or $100. grab a divorced 205, or keep your 200 and regear your axles ( i would swap).

i think you could do it for <4000. i know i can.

[mcinfantry]

i scaled the truck.
2500lbs rear axle
3650 front.

full tank, no troop seats.

i was 285lbs at the time, so figure me and co-driver pushed the curb weight over 7000 with chains, straps, gear.........

[MoparNorm]

....put the thing together to try and get a little road time. i dont think i had it on the road more than a week when i stopped to check on a guy who had driven into a ditch. i was rear-ended by a mitsubishi montero doing 55mph. she totaled her truck. she bent one bumperette (slightly) and knocked a hole in the nv4500 5th gear cover.

i got it back together in time for land between the lakes kentucky.

This then, is your rear damage?!
http://photos.imageevent.com/moparnorm/militaryrigs/websize/L%20M715%20After%20Wreck.jpg

[mcinfantry]

that is! she slid into me. she said she was scared to death, until i got out in uniform and she said she knew i wouldnt hit her!

i broke the seat back, the shifter (with my leg)

hers was totled.

[IHWillys]

mcinfantry

Did you ever turn up your 4BT or was it still at the fuel rate as when pulled out of commercial service?

I have two 3.7TD Hercules sitting in my garage that I'm not sure what to do with. They're 108HP/240lbft as they are not aftercooled. The aftercooled Hercs are rated 125HP/265lbft. Either way they are similar to the 4BT in the same application, stepvans, with the Cummins 3.9 rated 105HP and 120HP but with more torque than the Herc 3.7.

I'm flipping back and forth as to what size application is appropriate for one of these engines. I have a range from an old Scout up to a full size 4x4 van. I don't take these vehicles out on the interstate. The vast majority of driving in them is at 50 mph or below, brief periods of 65 mph but it's not necessary to be able to get to that speed to use these trucks the way I use them. Also I live at 5K feet altitude and weekly go to 7K feet, with multiple trips a year up over 10K feet. I'm used to my carburetted gassers really taking a hit on power by 7K feet. I think the turbo diesel will fair better due to the normalizing affect of the turbo. I don't tow anything so that's not a factor for me, just an occasional full load of camping gear with my wife and 4 kids along.

Anyway, your and others' posts are very informative and help guys like me to form an idea of what to expect before hand, which is of great value.

Ken

[MoparNorm]

Ken,
I don't have a 4bt, but I've had my Cummins 6 up over 13,000 ft. it ran just fine!
A non-turbo will start spewing black smoke under load at about 6,000 ft. the turbo, as you say, compensates.

[mcinfantry]

mcinfantry

Did you ever turn up your 4BT or was it still at the fuel rate as when pulled out of commercial service?

I have two 3.7TD Hercules sitting in my garage that I'm not sure what to do with. They're 108HP/240lbft as they are not aftercooled. The aftercooled Hercs are rated 125HP/265lbft. Either way they are similar to the 4BT in the same application, stepvans, with the Cummins 3.9 rated 105HP and 120HP but with more torque than the Herc 3.7.

I'm flipping back and forth as to what size application is appropriate for one of these engines. I have a range from an old Scout up to a full size 4x4 van. I don't take these vehicles out on the interstate. The vast majority of driving in them is at 50 mph or below, brief periods of 65 mph but it's not necessary to be able to get to that speed to use these trucks the way I use them. Also I live at 5K feet altitude and weekly go to 7K feet, with multiple trips a year up over 10K feet. I'm used to my carburetted gassers really taking a hit on power by 7K feet. I think the turbo diesel will fair better due to the normalizing affect of the turbo. I don't tow anything so that's not a factor for me, just an occasional full load of camping gear with my wife and 4 kids along.

Anyway, your and others' posts are very informative and help guys like me to form an idea of what to expect before hand, which is of great value.

Ken

i never turned a knob, screw or bolt to increase ANY power

[CGarbee]

Just to add my recent experience (every now and again I actually run the numbers on my truck...):

Fuel consumption, or, why I like my Cummins... I participated with the East Coast Convoy to the Aberdeen MV Rally in May. Round trip to Aberdeen with the ECC in my M37 with the Cummins 4BT, ZFs5-42 (0.76:1 fifth gear), 4.89 gears. Hardtop, bows mounted over cargo area, but canvas not mounted. 900r16 Michelin XZL tires (35" diameter). Max speed for trip about 55mph, had to keep it down due to trailing M35A2C for entire trip (mine, driven by my buddy Chuck) and due to the rest of the guys in the Convoy having similar pace vehicles so average was around 50mph (what I tried to hold it at)... Only had a M37 cab, a winch, and fourteen one gallon cans of string beans and potatoes in the bed for the ride up, ride back I had a M37 hardtop and a generator.

It was a 758 mile roundtrip. I burned 30 gallons of fuel... works out to 25mpg...
My "normal' leadfooted driving habits around town and on the highway yield an average of 17mpg, but I routinely am running at 75mph down the Interstate to work and/or doing the stoplight dragraces downtown...

FWIW: Current price of diesel in Raleigh is $2.85 gal, Unleaded regular is running $3.02 gal. Midwinter, diesel was priced the same as midgrade gas...

Every now and again I think that an ISB3.9 would be nice in my next rig, but I like what I am running. Never have turned anything up on it, but I am thinking that the higher rpm governor spring would be nice (be able to wind it up a tad more for the 3-4 shift when starting from a dead stop at the bottom of the hill a half mile from the house that has a stoplight at the bottom for instance, not because I want to run down the road any faster...).

[Gordon Maney]

Do you see any disadvantages to the ISB 3.9, other than cost and computer controls?

I imagine it would be quieter and more powerful? Does it have less vibration?

[mcinfantry]

finding adapters/accessories and such. how many have epa approval for road use? any?

[CGarbee]

Do you see any disadvantages to the ISB 3.9, other than cost and computer controls?

I imagine it would be quieter and more powerful? Does it have less vibration?

The ISB3.9-175 was installed as the standard power unit in the Freightliner Custom Chasis P3000 step vans (same as the old Chevy P30's, just Freightliner's version) with an Allison automatic until a couple years ago when Freightliner switched to a "Detroit Diesel" engine that actually is a Mercedes unit with a different valve cover... In other words, there are ISB3.9 engines that are just as EPA certified for use in a M37 or other repower application as the 4BT/BTA takeouts that folks are already using...

Cummins has not been paying much attention to the ISB3.9 in the US recently due to the efforts they have been making on the newer design ULSD engines, but they are still making the ISB3.9's in England, and elsewhere, and the parts are very available, you just have to have the $$.

That said:
Downsides other than the cost and electronic controls are that since they rearanged the components on the engine (fuel injector is driven off the flywheel instead of the front gear cover, for instance) you can't use the Dodge application ISB5.9 flywheel adapter, flywheel, clutch, or transmission like you used to be able to do with the 4B when you could use the 6B parts off a Dodge Ram. Bassically, Cummins made a special version for Dodge so that they could keep using the New Venture transmissions. Every other ISB can share parts, but they don't cross with the Dodge versions (as far as injector pumps, flywheel adapters, etc.).

Upside: A tad smoother, cleaner, more places to hang accessories, more power straight from the factory, setup to run with a SAE #3 flywheel adapter (negating the transmission problem mentioned above for my uses as I would go with either a Spicer 3053A or some other SAE transmission...). They also share the same block mounting points as the 4BT so they "should" be able to use the same frame mounts...

In all honesty, I have talked to a guy who has one that is being installed in a civilian Power Wagon, and I've looked at some data from Cummins, but until one falls off a tree near me (or I score a wrecked FedEx truck cheap), I'm not looking too hard at them...

So, an update to this post...
I just went over to the FCCC website and noticed that they have changed things again... Current "small" walk in van (step van) is the MT45 with the Cummins® 6.7L ISB07 200-hp 6-cylinder EGR diesel as the standard powerplant. So, no more little four bangers from them...

Incidently, for Mopar Norm: They have a page on their page that list ten reasons whey diesel is better in a bread van than gas... Follows closely some of the arguments that have been made on this site already.
See: http://www.freightlinerchassis.com/wvHome.asp

[MoparNorm]

Thanks for the 10 reason link Cabell!

I'm pretty certain that the decision maker in the post from Doc was tied somehow to the salesman for the gassers. Only nepotism or corruption could explain that decision!

[IHWillys]

Ken,
I don't have a 4bt, but I've had my Cummins 6 up over 13,000 ft. it ran just fine!...

This would be one more advantage of a turbo diesel over a NA gasser, altitude changes affect them less due to the turbo.

Ken