Here's my research for medium trucks:
Cummins ISC8.3- Excellent reliability, some fuel pump problems in early units (employs a Cummins computer FI system.) Powerful (300 HP+) Wet sleeve design for easy rebuildability. 24 valve head. An excellent choice in Freightliner, Pete, KW, others.
Smooth and Quiet. A D unit dream.
Detroit Series 50- Powerful (300 HP+) 4 cylinder with overhead cam. In Freightliner FL106 only as it needs a high hood. Shares big Series 60 design and has excellent reliability. Smooth and quiet, has a balance shaft. Computer allows it to idle on 2 cylinders for economy. Wet sleeve design also. Wish it were available in trucks other than FL106. A D unit dream also.
Cummins ISB5.9- Parent bore little Cummins. Essentially the engine used in Dodge Ram pickups, but with a bigger (15 quart) crankcase. Bosch computer fuel injection. HP up to 275. If you change its oil a lot, it will go past 500k miles easily. Inexpensive to run and rebuild. Not near as torquey as bigger displacement engines. Great for C unit trucks.
Caterpillar 3126/3126B- 7.2 liter 6 cylinder engine. Power up to 280 HP. They are powerful when new and run away from everything, but are not very reliable. Usually die around 400-500k miles and cost $10-12k to replace. They are usually so totally shot that a rebuild is not feasable. HEUI oil powered fuel injection system causes most of engine's problems down the road. Need super clean oil at all times and general repairs are expensive too. Stay away from this thing.
Older Cummins C8.3 (on used market, no longer available new)- Big, but not generally powerful (225-260 HP). Bosch mechanical fuel injection is excellent. Cooling system must be kept top notch or C8.3's head likes to crack. No intake preheat so ether must be used to start it in very cold weather. Very reliable if maintained, and cheap to rebuild with wet sleeve design. A very good choice in used D truck market. It is hot and noisey however.
Older Cummins B5.9 (on used market, no longer available new)- These parent bore engines can be found in a lot of used medium trucks esp. Freightliner and Ford. Again a Dodge Pickup engine with 15 quart crankcase. Bosch mechanical fuel injection is great. Engine is rated for 350-400k life, will easily go past 500k with excellent maintenance. Cheap to rebuild or replace. HP up to 230. A good engine for a used C/D unit for beginner. No preheat so keep some ether with you. Dependable but noisey.
International DT466/466E- Ok, I have ran these engines locally but have no clue how they hold out on the highway (not enough data). I know it is a wet sleeve inline 6 cylinder engine and the "e" variant has a computer fuel injection system. I'll take it the 466 is CI so that makes it around 7.6 liters. I'm pretty sure these IH built engines are really reliable, but I don't think they offer up much horsepower. (I'm just judging that by I don't recall ever being passed by one lately.) If someone out there is running IH power, please set me straight on this thing's ability on the highway.
International T444/444e- The infamous Ford powerstroke. Possibly the best little diesel for a van, cube truck, or hotshot pickup. An IH built competitor to the Cummins ISB. I wonder how the two compare neck to neck? I think the 444 is available in Ford F600-700 chassis for straight trucks, as well as International chassis. It is a parent bore V8 engine. Big use in school busses.
If anyone else has an engine or facts they would like to add or dispute, please feel free! How 'bout some gas engines for vans?
-Weave-
(This was fun- took me 1 hour and a couple of beers to compose
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