1988 International short bus

[Tankinyz]

Hey guys, so little question mostly, I’ve got an 88 international short bus, its got a few kinks that I need to figure out to get it road worthy for traveling this season, it’s already got a conversion setup with bed, couches and a table and hvac external unit and plugs powered by a generator. The motor is a 7.3 idi non power stroke ford with an Allison transmission. I use it to pull my drift car to race events and camp inside on events that take longer then a day to reach. The only issue being, the bus at max espies goes 65, I’m needing it to go atleast 75 or so, it’s only a 5 window bus and I’m scared to go up hills or mountains or go thru Texas towing and catch a impeding ticket. I read somewhere I could turn the injection pump up but that the big tires do not like going over 65, is there a way to convert the big wheels into a smaller dually setup? I’ve searched and found no conclusive results . Or otherwise can I scoot by on just turning the injection pump up?

 

[tradertim54@gmail]

The single best thing you can do is turbo from a junkyard! and bigger tires ...what size rims ? that bolt pattern is weird for a bus and what is your gross weight rating..

 

[tradertim54@gmail]

I looked a little closer at your images and it looks like you already have truck tires on the old style split rim. so larger tires are out . yes the injector pump could be turned up and bigger exhaust put on it, but a mechanic friend told me that to add a turbo probably wouldn't work because the intake can't handle the boost pressure. So... the turbo thing I said isn't right. Turning up the injector pump will just put more fuel to it, it won't necessarily give you more torque which is what you need. It sounds like that engine is under powered for what your wanting it to do.The only other thing I can think of is to see how much weight you could shed, which probably isn't a good option. I've been looking for a vintage bus 40s-50s-60's era. I would then buy a later model bus to use as a donor for the engine, drive train, and suspension. That will be my next bus if I live that long. Good luck I wish I could be of more help.

 

[CHEESE_WAGON]

Auto trans can only take so much torque and power anyway. And smaller tires will slow you down, not speed you up. You need to re-gear the differential to higher (numerically lower) ratio. Agree to disagree, but those look like Budd wheels to me, not split rim. Conversion perhaps? Lug circle is odd for a bus. I've seen five-lug and six lug on Chevy P RV chassis with independent suspension, but never on a bus / truck over 3-ton chassis. Perhaps this is a Ford F53 (GM P-series equivalent) chassis? S1700 is lighter duty, perhaps six-lug was an option.

Try this thread, it seems to have some power tips for this engine and suggests a turbo IS possible. Just don't get boost crazy, the trans will only take so much.

https://www.ford-trucks.com/forums/845868-7-3-idi-power-upgrades.html

 

[cadillackid]

dont stand on your hood!! it is easy to damage and expensive to replace!!!



I have spent quite bit of time drivin g 62 or 63 in texas in my DEV bus.. it goes 68 but I dont like it there.. ive driven all over the darn state and had plenty of cops pass me and I didnt get any impeding tickets. ive even passed a truck or 2.



its not a race car its a school bus. and an old one..



the 7.3 IDI is a good motor and you can turn the pump up a bit.. but the most common automatic transmision with that engine was an AT545.. that transmission wont take much towing and turning power up.. it will overheat and nuke esp in texas.. a big trans cooler can help. but nevertheless there are design limits..



converting to smaller tires will slow your max speed down unless you re-gear the rear end.


to regear you would either have to do a full axle swap or find a rear 3rd member that matches yours and swapo the ratio..



if your top speed is limited by the engine RPM governer now then you need to regear to a a "taller" gear.. ie if you have a 5.13 ratio now you would go to say a 4.10 or 4.44 ratio to achieve a higher top speed..



the taller gear you use, the less hill climbing torque you will have..

 

[CHEESE_WAGON]

 

[dzl_]

Love this era of international!

 

[cadillackid]

Love this era of international!

79-89, the S-series!!! rode these to school brand new.. my favorite years of IH along with loadstars

 

[Truthseeker4449]

Agree to disagree, but those look like Budd wheels to me, not split rim. Conversion perhaps? Lug circle is odd for a bus. I've seen five-lug and six lug on Chevy P RV chassis with independent suspension, but never on a bus / truck over 3-ton chassis. Perhaps this is a Ford F53 (GM P-series equivalent) chassis? S1700 is lighter duty, perhaps six-lug was an option.

Look at 12 o'clock relative to the ground? See the big split in the rim? Looks pretty similar to the split rims on a 80s Ford cabover fire truck that lives in the corner of the shop where I work. Looks like same bolt pattern too. How or why this bus would have that hub pattern is beyond me, but it strongly looks like a split rim or a Budd wheel in need of replacement.

Now to be honest I wasn't even alive when split rims were the norm or even when they were being phased out. That fire truck is the only one I've ever seen in person, so I recognize that I could be wrong.

 

[Booyah45828]

It's definitely a split rim, and definitely is a light load axle with the 6 lug rims.

Pretty much everything you have wheel wise is obsolete and undesirable. Even the cast spoke rims that I have are undesirable, but because they made them in the millions 30 years ago, they're still sticking around.

Listen to Christopher, I doubt you'll get an impeding ticket. If that is all the faster it can go, then what do they expect you to do? A lot of older vehicles are like that because the national speed limit was 55 mph at one point in time. Just stay out of the way in the right lane and do the best you can.

 

[Booyah45828]

If you want to go faster. You need to do 2 things: more power, and more/faster gearing.

I have an 1984 s1700 (S1753 is the school bus version of the IH S1700 FYI). Mine has the 6.9 IDI, which was superceded by your 7.3 IDI. So I know a thing or two about buses like ours.

These engines are pretty durable, just low on power, especially in NA form.

So, to get more power, a turbo isn't an option, it's a must. And if you're really serious about it, an intercooler is mandatory as well. Hypermax makes a bolt on turbo kit for our engine in the S-series Internationals. But they're pricey at like 3 grand. You can buy a kit off a ford pickup out of the junkyard, and fabricate that to fit if you have the skills. You can also build your own kit with any turbocharger available, like a few others have done.

If you're looking to put boost to any IDI, ARP head studs are also a must. The added atmosphere when combined with the high compression of an na IDI is too much for the head bolts, and there is a high probability of blowing gaskets without the studs.

One more thing,
If you don't have a turbo, don't touch or turn up the injection pump. There is no point in adding more fuel when you're already maxed out on air.
Once you have a turbo, then you can turn up your pump. OR add a bigger pump from one of the guys that build those sorts of things. But being NA, there isn't much you can do aside from minor adjustments, which will only get you minor gains.

 

[Booyah45828]

Once you have the power, your next step is getting that power to the ground.

Most buses are built gear bound, because they spend most of their time below the speed limit picking up and dropping off kids. So some sort of rear gear and or transmission swap is a must if you're wanting to go the speed limit and beyond.

The easy way to go faster in any bus is to swap the rear 3rd member to a lower numerical ratio. Going up hills is a different story, though. There's a reason most semi trucks have 10+ speed transmissions, and that's so they can best match their power to their road speed. Matching the power to your road speed allows for faster acceleration because you're always in the sweet spot of power to MPH. Putting a taller gear in the back will cost you your acceleration speed, because your engine will then be out of that sweet spot more often.

You have 2 options for more gears, one is swapping in a manual transmission and the associated hardware. That will allow you to use one of the aforementioned 10+ speed transmissions out of a larger truck.

The other option, which will give you the best of both worlds, is to go to a modern automatic. They come with 6 speeds, with the last 2 being overdrive, giving you the highway capability that you want, with the acceleration that you currently have.

They also have a lockup torque converter, use modern synthetic fluids, and have adaptive shifting. All of which creates a longer more durable product compared to the at545 that you currently have.

One nice caveat about the IDI/at545 combo that you have, is that the IDI has a higher rpm powerband compared to that of most other diesel engines. That higher powerband is better suited for the stock high stall torque converters used in the at545, because the higher rpm lowers the amount of slip in the converter. So you typically don't have to worry too much about high trans heat.

But a fluid temp gauge is still highly recommend for any AT545.
It's really a good recommendation for any bus, so long as you know what you're looking at.