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Old 03-03-2006, 04:17 PM   #1
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Engine Swap --- or Rebuild ???

Hello everyone --- I am new to this forum, but not new to owning a school bus. I am now on my second. It is a 1984 International with a v8 345 gas engine hooked to a 5-speed, with Air Brakes. It is completely converted with a bathroom, water, tables, overhead storage, etc. I have been a Scoutmaster for many years now, which got me into bus conversions. It is a great way to travel, hauling everything you need in one vehicle. Been to Canada with it, and last year we went to the World Lumberjack Championships in Hayward Wisconsin. This is a great forum, and I finally decided to join you guys --- as I need some help and advice.

It's a sad story; buy my v8 345 bit the dust on its first long trip last summer (to the Lumberjack Championships that I mentioned earlier). The engine had just been rebuilt by the School I bought the bus from, and was running beautifully, however, I was unaware of the relatively low rpm red-line of these International engines, having a previous Ford that would take 4000 rpm all day. After running it for 14 hours straight at what appears to be red-line (3600 rpm), it finally melted a piston.

This leads me to my question and need for advice from you guys. My options are to rebuild the v8 345 working with a local engine rebuilder using internal parts that allow the engine to rev. higher without melt down (forged pistons, etc). Go to a larger v8 392 or 404 gas engine, or swap in a diesel. Irregardless, I believe I need to add a 2-speed rear axle to keep the RPM's down, but will likely need more power to compensate for the higher gearing. I want to be able to run it at 65mph without hurting anything.

I know by reading several of your comments in the past that most of you like a diesel engine --- but how hard is it to swap out a gas engine for say a diesel DT466? Is it worth the work, and has anyone done it and know what is involved? I am fairly mechanical, having rebuilt a few engines, and have always done all my own maintenance. I have all the tools, lifts, etc. to get the job done, but I don't want to start something that will end up being a nightmare. ------ Advice ?? ------
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Old 03-03-2006, 05:09 PM   #2
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gas to gas swaps from different manufacturers can be a headache. I REALLY don't think you want to mess with doing a gas to diesel conversion from dissimilar manufacturers. I've done my fair share of these types of swaps in other vehicles (I'm an avid fourwheeler) and I can tell you that no matter how much to plan and budget it will cost twice as much, take four times as long, and require eight times the profanities to get it done.

On the plus side you have a very good engine. The 345 seems to be the holy grail of the IHC engines for guys running Scouts and the trails and I can't disagree with their reputation as being stout performers. Every one I've ever seen has had a forged crank, forged rods, etc. They really are built well, but as you learned....they have a relatively low redline. My suggestion would be to rebuild what you have. Chances are you will only need to bore it (or even just hone it if you're lucky) and put some new gaskets, pistons, and rings in it. Though it's not cheap, it is easily your cheapest option short of running a used motor you pull out of some other vehicle.

The two speed rear end is of course a good option though might be expensive. Another option might be finding an aux. tranny. A final option if you really want to get frisky might be to take a divorced type rockwell transfer case and run it backwards so that low range is now a huge overdrive. I know it sounds kind of booty fab, but I've seen worse done for cheaper with god results

The Scout owners I have talked to have often mentioned Northern Auto Parts as their source of engine parts. You may well want to join a cornbinder forum of some type to get some input from those more experienced. They may even have some options to sneak a few more revs out of that engine.

Hope that helps and feel free to contact me with any question you may have...I can atleast try and line you up with the people with the answers pertaining to those 13 letter $hitflinger motors
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Old 03-03-2006, 06:30 PM   #3
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Repower or rebuild.

There is no substitute for power. For the demands of powering a heavy bus, nothing works as well as a diesel engine. Nearly all buses can be powered with just about any engine made. Lately it seems a complete used schoolie can be gotten for less money than repairing a gas engine. Many buses with great engines and an Allison auto trans can be bought for about $2500. I have bought about 12 used diesel engines for a variety of applications and have not been disappointed. Diesel engine are very spendy in having same overhauled, but the life span is very long. Getting a used schoolie will supply any and everything required for a engine change. If there are any doubts, make a comparison list. Diesel will win as the lowest cost repair. The gas engine can be repaired and sold. Either a lower numeric rear axle ratio is a better idea than a 2 speed. Operating a 2 speed rear axle requires some talet as a 410 or 393 requirews just drive and drive. Spend some time on line and use the yellow pages to search out engines and trans and a schoolie.
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Old 03-03-2006, 06:48 PM   #4
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In my opinion, a two speed rear end really is not all that complex to use. There is absolutely no reason when he couldn't start in high and never have to use low unless it was a real low speed operation or some very demanding work.

As for gas versus diesel...I own a diesel, but that's because that's what was available. Certainly I do like the benefits of the diesel, but there are some higher costs associated with it that might never be made up if a person only operates their skoolie a few times per year. If a person where going to buy a new skoolie I would of course recommend a diesel, but if what they have is a gasser, that's what it should stay is kind of the way I look at it. I once converted a 2wd truck to 4wd for a friend. While it was possible, in the end it would have been better to just buy a 4wd truck and either keep the 2wd for putting around town or perhaps selling it to buy said 4wd. Converting stuff is's a personal passion of mine....but there are limits as to what is feasible and practical and I really don't think a diesel swap on a gasser skoolie is all that practical.
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Old 03-03-2006, 06:54 PM   #5
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what i would do if it were my bus..........

I'd buy a new bus with a DT series diesel engine and for under $2k if you keep your eyes open and re-convert the interior. I'd take the interior swap over the engine swap for it's reliability. IT doesn't require a professional to do thing to the interior of a bus, but yo ubetter know what you're doing if you're gonna overhaul an engine.

Swapping a gas for a diesel will prob require a suspension upgrade to the front of the bus. I am pretty sure that diesel engines tend to weigh significantly more than a gasser.

I wouldn't be afraid of a big gas motor. Fuel economy might be not as good as a diesel, but gas motors of the same displacement tend to be much higher performance....although the gas is lower on torque. The manual trans is a big bonus. If you're into spending money, a rear end change would be very adventagous.

just my $.02
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Old 03-03-2006, 08:37 PM   #6
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If you go to and look in the Indianapolis section of auto parts, go back a few days and there is a 345 with trans out of a dumptruck for sale for $1000. Might be worth checking out, or might be junk, who knows!
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Old 03-03-2006, 10:15 PM   #7
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Or you could probably find a IHC for sale with a 345 or 392 (easy swap) for sale for next to nothing.

I have a 345 and run it at readline the entire time on the interstate with no problems. These engine are built like tanks, ask any off roader and you must have just gotten a little bug in yours.

Also I run an electric radiator fan in addition to the mechanical fan, this may be something you want to consider, or even disabling the fan clutch if you have one.
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Old 03-04-2006, 08:14 AM   #8
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You need to re-gear your rear will be much easier on the engine and the driver.

A 392 is a bolt in swap. A diesel conversion will require essentially re-engineering the entire drivetrain.
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Old 03-04-2006, 09:31 AM   #9
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Having been in a similar situation, I can understand your desire to go for max power since you're going to have everything torn apart anyway. When the 350 in my '64 skoolie died, I opted for another 350 as the easiest/cheapest route considering everything was already there and matched up perfectly. Also, as Jarlaxle suggested, when I first bought the bus I had the gearing in the differential changed for a higher top end. I had it done at a place that rebuilt and repaired semi's and was very pleased with that decision for many years. I had researched a 2-speed axle but it would have required buying and installing a LOT of expensive hardware that was no longer available for a 1964 60 series bus. There was only junk yard stuff available and I wanted a new drive train. For my money, Jarlaxle is right unless you are up for an entire interior rebuild in a different rig. All things considered, swapping out the same sized motor and regearing the rear end is the quickest, most hassle-free, and inexpensive way to go. Just my opinion and worth every cent you paid for it. Ha!
1993 Amtran (Ward) 77 Passenger body on an International frame. DT360, Allison 545 AT. The avatar is my first skoolie, "The Rocket" may it Rust In Peace. Follow the links at the bottom to see the horrible details at
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Old 03-06-2006, 09:57 AM   #10
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All --- thanks much for your advice. Seems the way to go is just rebuild what I have. I had heard that the 345 was a tough engine --- just frustrating that I had trouble with it.

About the 2-speed rear axle. How do I know what to look for from a compatibility standpoint. For example, will a 2-speed fit out of a Loadstar dump truck.
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