Bus Engines (ADVICE NEEDED)

[WanderingForest]

Hi everyone. I'm new to the skoolie community I am selling my house this spring, and looking to purchase and convert a skoolie over the spring and summer. At this moment I'm still looking for a bus to convert, but I know I need a full size bus, as I will be living in it full time, and want my son to have his own space in the bus as well.

My question is about engines for full size buses. I had read that some engines are not good for skoolie conversions as they are already at about their max pulling a full size bus. I had read that torque is what affects how much weight the engine can pull... and it seems I need an engine with at least 900 lbs-ft torque? (correct me if I'm wrong, or if there's another way to know if the engine can handle the weight of a converted full size bus)

The buses I'm currently looking at have a Cummins 8.7 engine, a cummins mechanical 12 valve engine, a Cat C-7, and a Cat C-9 engine. Are these engines powerful enough for what I'm looking for? Which ones would you recommend, or warn against? Thanks for all your help, and I'll probably be posting in here a lot for the next several months

 

[fo4imtippin]

Don't worry about the power. The manufacturer designed the engines to be able to get around at full load. They all take awhile to get to speed when fully loaded. It's not like a car where you zip around. Full size school buses are usually between 32k and 37k. I think the best interstate speed is about 60. If the rear end and transmission are right, they all go 60 even the weaker engines.



This is totally subjective, but I would focus on finding something that is the most affordable to repair. Big engines require heavy duty mechanics and parts are more.
International T444e and Cummins 5.9 are pretty affordable engines because they are found in pickup trucks.



Dt466 and Cummins 8.3 are awesome engines, but have their parts are a bit more and your diesel pickup mechanic may not be help out.



Cats are okay, but parts kept me away.


I would just change your thinking to factor cost of ownership. Good luck on your search!

 

[mmoore6856]

why do international pistons cost more than cat ???? i bought both and the price myth is still prevalent. if your not good with electronics go with a mechanical engine. i worked on all these engines i found that cat owners are loyal for a reason but have seen many cummings go the distance also. i avoided the international as i dont like a rolling oil slick. (my cat sits in a concrete driveway for 5 years and there is no oil on it. if it leaks when you buy it it will keep on leaking . some oil leaks can run thousands of dollars to fix. never believe that (its just a cheap gasket) when they are trying to sell you a bus or they would have fixed it

 

[cadillackid]

why do international pistons cost more than cat ???? i bought both and the price myth is still prevalent. if your not good with electronics go with a mechanical engine. i worked on all these engines i found that cat owners are loyal for a reason but have seen many cummings go the distance also. i avoided the international as i dont like a rolling oil slick. (my cat sits in a concrete driveway for 5 years and there is no oil on it. if it leaks when you buy it it will keep on leaking . some oil leaks can run thousands of dollars to fix. never believe that (its just a cheap gasket) when they are trying to sell you a bus or they would have fixed it

or if its jus ta few drops you drive it and who cares... ever notice all the oil spots at truck stops in the truck lots? those guys run 600K+ on those engines and oops they drip a few drops of oil...



big puddles? yeah something to worry about....



mechanical engines are the easiest to DIY on.. but most people know that and those engines may very well cost you a bunch more to purchase.. and find the bus is deteriorated (but it will run exzcellent and be easy to work on).. till the old bus body falls apart....



but really thiough up through about 2003 is prime.. after that emission controls started ocming in.. and they do suck to work on.. or you need better skills...

 

[flattracker]

I prefer diesel engines. My "old Crown" has a Detroit 671 and has been reliable but under-powered.The "new Crown" has a Cummins Big Cam I 400 upgraded to a Big Cam III. It has more than enough horsepower to get the job done.


The "old Crown" got 10 mpg reliably and I don't yet know what the fuel economy will be with the "new Crown".


Both Crowns are mechanical.


I have two F250 pickups one with a gas 460 ci engine and one with the IDI turbo diesel engine.


The diesel F250 is mechanical (except for the E4OD trans) and the 460 gas is computer controlled with emissions. I like the diesel one better.
The gas pickup gets 12 mpg with sufficient power (but not great power)
I used to have a E350 former ambulance with the IDI non-turbo diesel that I used for a race van when I still raced and I liked it until the engine ate it.


I believe there is a learning curve for working with diesel engines, but once understood they are not scary to work on.


The Cummins Big Cam engines were used in 18 wheelers and made to last > 500 K miles without major overhaul and up to 1,000,000 miles with overhaul. They were designed to be rebuilt if needed. They were made to work hard day after day.
That said, very few buses will have a Cummins Big Cam, some Crowns came with one and maybe Gillig?


I have read a number of posts about buses that have International 466 engines, which I understand is a version of the Power Stroke diesel that came in Fords. Until last year I had a 97 F250 with the power stroke and it had over 400 k miles one it and it is still going. In the time I had it no major repairs were made to it. I think the rest of the truck will probably fall apart before the engine goes bad. That truck certainly had the grunt needed to pull heavy loads and I got 18 - 22 mpg with it (not pulling a trailer)
The Power Stroke is run by a computer and can be "chipped" for more horsepower. I had no emissions issues while I had it.



Understanding what use you will have for your skoolie can make a difference to what engine you will want. If you will drive your bus once in a blue moon and not very far maybe your engine choice is less important. (maybe you live in it and only drive to move it to a new spot to live at).
If your bus is intended to drive across the country then your engine choice is very important. Some parts of the country have lots of steep grades where grunt is important. If you will never drive on freeways/interstates then top speed is less important.


For me, I want to be able to drive on the freeways, climb steep grades, and drive hundreds of miles per day when I travel, so engine choice is important to me. A large fuel tank is important for that also. Being able to go 600 miles without fuel stop is important.


One last thought - If you go with a gas engine and don't drive your bus but very occasionally worry about the gas going bad as it will. Avgas 100LL will not go bad unless contaminated by water but it will be expensive and most folks cannot drive on the ramp at the airport for a fill up.

 

[djdalfaro]

For me, it came down to a list of decisions;

1. Gasoline vs Diesel? For a mid-duty bus, diesel is the way to go. If I had gone with a cutaway, maybe I would choose differently.
2. I6 vs V8? I6 are inherently more powerful, reliable, etc...
3. Mechanical Injection vs Electronic Injection? I like to be able to work on my own cars. I like to know that if something isn't working right, I can find a mechanical piece and replace it. I've read too many posts here and on FB, "HELP, my bus is in limp mode. HELP, my bus won't start. etc..."
4. Turbo vs Naturally aspirated? Turbos are the way of the future. All modern diesels are turbo, you'd have to go back to the early 90's to find a non-turbo diesel IIRC.
5. Sleeve vs bore? Sleeve motors can be easily resleeved inframe. Bored motors have to see a machinist.

So my list of prospective engines narrowed considerably
Navistar I530, bosch p-pump, wet sleeve, never actually heard of a non-electronic one in a bus, so I put this one down as a pipe dream.

Cummins 6CT8.3 this is pre-ISC, 12 valve, bosch p-pump, wet sleeve. Would be a good choice as they are mated to more capable transmissions like the MT643, but I was hunting for a 6-8 window bus, and I've not seen one in a bus that small. BlueBird chassis.

Navistar DT466 NGD, bosch p-pump ~93-~98. Can be found from about '93 to about '98, but after the DT466E came out in ~'96, you have to verify visually that it's the mechanically injected version, as the badging doesn't always match. International chassis.

Navistar DT408 NGD, same as above, just a de-stroked DT466 block with a few minor changes. Only came out for 2 years ~93-~94, until the T444E became the base model motor for International chassis.

Older Navistar DT motors came in both 466 or 360, the injection pumps get less desirable as you move further back from ~'93, starting with the MW-pump which is almost as good as the P-pump.

*Honorable Mention* Cummins 6BT5.9 this is pre-ISB, 12 valve, bosch p-pump. This motor is the only one on my list that isn't wet sleeved. It has a cult following and is a proven reliable motor. Bluebird and Ford chassis buses.

If I made any mistakes, feel free to correct them.

 

[djdalfaro]

I have read a number of posts about buses that have International 466 engines, which I understand is a version of the Power Stroke diesel that came in Fords.

Almost. The Navistar T444E is the one that Ford uses as their 7.3 Power Stroke. I'm sure there are some differences in many of the accessory parts, but to my understanding, it's the same block.

 

[WanderingForest]

I’ve heard about how the injection systems changed due to emission regulations. Do you know what date an international/navistar dt466 engine has to be to be a mechanical injection? I am looking at a 2006 bus, and they just say dt466, not dt466e, but I know that the electronic engines may still be listed just as a dt466 engine. As well, is there a way to tell the injection system just based on looking at the engine?

 

[WanderingForest]

Thanks everyone for the advice so far. There’s been a lot of useful information shared

 

[cadillackid]

I’ve heard about how the injection systems changed due to emission regulations. Do you know what date an international/navistar dt466 engine has to be to be a mechanical injection? I am looking at a 2006 bus, and they just say dt466, not dt466e, but I know that the electronic engines may still be listed just as a dt466 engine. As well, is there a way to tell the injection system just based on looking at the engine?

the old mechanical DT466 engines.. (94-96 (and sometimews as late as 98 in Amtran Busses)) were the best generation of DT466 mechanical.. they were called "NGD". you can identify them as they use a Serpentine belt instead of V-belts.. and you will see 6 Hard metal fuel lines going from a pump on the side of the engine up to the head (1 for each injectors).


prior to 94, you have the same metal fuel lines but you have V-belts instead of serpentine.. these are also ver ygood and are mechanical...



starting in late 94 the 'DT466E' came out.. gen 1 466E engines look similar to the mechanical except you wont see any hard metal fuel lines or a pump on the side of the engine.. there will be some wires going into the valve cover...


in 97 the 466E NavPak was released.. these are easy to spot as they have a big "
Brick" sized computer hanging off the side of the engine with 2 large wire cables connected... these went through late 03 / early 04.



at this time, out came the 466E EGR.. it had a VGT turbo, an easy to spot EGR cooler setup on it, no longer has the monster computer on the side, and has lots of wires up on top and into the valve cover.. on the 4300 / 4600 etc trucks.. the nameplate was changed from '466E' to just 'DT466'... these were level 1 emissions and were thre beginning of the degradation of the ultimately bullet-proof 'DT466 (E)' that we had come to know and love in previous decades..



in 2007 / 2008 the name was changed to "Maxxforce DT" and full on emission equipment was present...


-Christopher

 

[Ronnie-SKO]

something that has not been mentioned is often the same engine can have different HP ratings. It really depends on what the school district orders. So look on the tag on the engine and see what it says. The more power the better.


Also route buses tend to be geared lower and have lower hp then an activity bus.



Are you going to do a lot of highway miles, or more back roads?

 

[HamSkoolie]

I have read a number of posts about buses that have International 466 engines, which I understand is a version of the Power Stroke diesel that came in Fords.Until last year I had a 97 F250 with the power stroke and it had over 400 k miles one it and it is still going. In the time I had it no major repairs were made to it. I think the rest of the truck will probably fall apart before the engine goes bad. That truck certainly had the grunt needed to pull heavy loads and I got 18 - 22 mpg with it (not pulling a trailer)
The Power Stroke is run by a computer and can be "chipped" for more horsepower. I had no emissions issues while I had it.

It's already been mentioned but the DT444E is the engine put into the Ford pickups and called SuperDuty. The base engine is the same but accessories, computers, fuel pump, and other things are different.
The DT444E has a B10 of 250,000 miles and a B50 of 500,000 miles. It is rated for vehicles up to 75,000 GVWR so a 32,000 pound GVWR bus isn't even at 1/2 the engines rated capacity. Properly maintained, it's a great engine.
I have a 7.3 liter Ford SuperDuty and a DT444E in the 40' RE 3000 AmTran from 1996.

 

[HamSkoolie]

4. Turbo vs Naturally aspirated? Turbos are the way of the future. All modern diesels are turbo, you'd have to go back to the early 90's to find a non-turbo diesel IIRC.

Turbo's also mean that you don't lose power as you climb hills. Normally aspirated engines are sucking in less air with every foot of altitude due to the thinning atmosphere. With a turbo, that doesn't happen as the turbo is pumping air into the cylinders under pressure and so power remains steady.

 

[cadillackid]

Turbo's also mean that you don't lose power as you climb hills. Normally aspirated engines are sucking in less air with every foot of altitude due to the thinning atmosphere. With a turbo, that doesn't happen as the turbo is pumping air into the cylinders under pressure and so power remains steady.

I remember driving an old diesel in the rockies.. no turbo and just black smokin our way up in 2nd gear at walking speeds!


I was glad when our next diesel had a turbo.. same engine, same kind of truck(scout).. and a *LOT* better results!

 

[HamSkoolie]

I remember driving an old diesel in the rockies.. no turbo and just black smokin our way up in 2nd gear at walking speeds!


I was glad when our next diesel had a turbo.. same engine, same kind of truck(scout).. and a *LOT* better results!

The Scout was an awesome vehicle. Now days it's like pulling hens teeth to find one available.

 

[Dingbat-SKO]

why do international pistons cost more than cat ???? i bought both and the price myth is still prevalent. if your not good with electronics go with a mechanical engine. i worked on all these engines i found that cat owners are loyal for a reason but have seen many cummings go the distance also. i avoided the international as i dont like a rolling oil slick. (my cat sits in a concrete driveway for 5 years and there is no oil on it. if it leaks when you buy it it will keep on leaking . some oil leaks can run thousands of dollars to fix. never believe that (its just a cheap gasket) when they are trying to sell you a bus or they would have fixed it

I would avoid a diesel engine. Gasoline is $3.89 and diesel is $5.49 a gallon this April 27, 2022. That's 41% higher. if a gas engine gets 12 miles per gallon your diesel should get 17 mpg. Assume the worst an the diesel gets 6 mpg. And you drive 150,000 miles and consume 150,000 divided by 6 = 25,000 gallons @ 5.49 = $137,250 just for diesel fuel.

 

[Albatross]

I would avoid a diesel engine. Gasoline is $3.89 and diesel is $5.49 a gallon this April 27, 2022. That's 41% higher. if a gas engine gets 12 miles per gallon your diesel should get 17 mpg. Assume the worst an the diesel gets 6 mpg. And you drive 150,000 miles and consume 150,000 divided by 6 = 25,000 gallons @ 5.49 = $137,250 just for diesel fuel.

Not sure where you are, but that's awful high, even for diesel.

But the nice thing about diesel-cycle engines is that you can utilize a lot of alternative "fuels" if your pump and injectors can handle it. I've toyed around with black diesel before, and there are whole conversion kits for used fryer grease if you don't mind dealing with the lower pH and changing out all the gaskets to something that can handle it. And then there's kerosene and other fuels that can be utilized if you have an 'actual' diesel engine, and not some modern crippled PoS that's running with a DEF system.

There's probably something wrong with your motor/transmission/load-out if you're getting 6 mpg in a diesel powertrain. If you factor in the beefiness of the motor, as well as the more expensive maintenance, but also that diesels are capable of hitting a million miles regularly if properly cared for, the money is actually on a diesel instead of an Otto-cycle gas motor.

And when you consider the weight that most of us are moving around...
Gas engines simply do not cut it any way you slice it.

Fuel costs are a known, and they are also known to vary significantly--which is why it is expected that fuel stations have their prices on a sign out front if they are open. If you're paying that much for diesel, there is something wrong with your situation.

 

[HamSkoolie]

I would avoid a diesel engine. Gasoline is $3.89 and diesel is $5.49 a gallon this April 27, 2022. That's 41% higher. if a gas engine gets 12 miles per gallon your diesel should get 17 mpg. Assume the worst an the diesel gets 6 mpg. And you drive 150,000 miles and consume 150,000 divided by 6 = 25,000 gallons @ 5.49 = $137,250 just for diesel fuel.

Not sure where you are but you might examine your state fuels taxes to see if they explain that price spread.
Here in S. Oregon today, the cheapest gas and diesel prices available within 10 miles are 75 cents apart while the highest are within a nickle of each other. The gasoline spread from low to high is DOUBLE the spread for diesel.
Also notable is that the gasoline engine is going to require more maintenance and fail long before the diesel in heavy duty applications.

 

[Albatross]

Not sure where you are but you might examine your state fuels taxes to see if they explain that price spread.
Here in S. Oregon today, the cheapest gas and diesel prices available within 10 miles are 75 cents apart while the highest are within a nickle of each other. The gasoline spread from low to high is DOUBLE the spread for diesel.
Also notable is that the gasoline engine is going to require more maintenance and fail long before the diesel in heavy duty applications.

Yeah, that sounds like some commiefornia screw-jiggery going on.

Those prices are insane; right now across the street from work diesel is about 4.5, and gas is almost 4. And the last time I looked, diesel was something like $3.89.

I'm pretty sure that the problem DingBat is talking about is more one of location, rather than a national thing.

 

[Johnthebusboy]

Don't sell your house until you have completed your bus conversion and lived in it for a while.

The best diesel engine is the one that the previous owner took proper care of.

I like mechanical control more than electronic control because there are fewer parts to break.