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Old 07-04-2019, 05:00 PM   #1
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3208 Cat Questions

Ran across a skoolie for sale locally... 80s Saf-T-Liner. Price seems good, according to the seller it is a Cat 3208 with Allison MT643. I'm not altogether familiar with the 3208, is this one of the early HEUI engines? Anything good or bad I should know?
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Old 07-04-2019, 05:04 PM   #2
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Originally Posted by CHEESE_WAGON View Post
Ran across a skoolie for sale locally... 80s Saf-T-Liner. Price seems good, according to the seller it is a Cat 3208 with Allison MT643. I'm not altogether familiar with the 3208, is this one of the early HEUI engines? Anything good or bad I should know?
Its an all mechanical engine but its heavy and under-powered.
Not the best but they're ok. The internals are small and its a parent bore engine. When they go out its best just to swap for something different.
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Old 07-04-2019, 05:09 PM   #3
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Depends on the price you didn't mention.
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Old 07-04-2019, 06:01 PM   #4
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Its an all mechanical engine but its heavy and under-powered.
Not the best but they're ok. The internals are small and its a parent bore engine. When they go out its best just to swap for something different.
Interesting you mention that, I reread the ad and it mentions needing a starter and batteries. Which is not in and of itself that big of a deal I guess, I found a new starter on eBay for $200. But sometimes people will lock up an engine and just say it needs a starter, which can't be proven otherwise until the work is done, at which point you're stuck with a paperweight. I imagine a 3208 is not an engine that can be turned over with a breaker bar.

So, assuming the worst, what are viable replacements for the 3208 that will bolt to the MT643?
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Old 07-04-2019, 07:41 PM   #5
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Interesting you mention that, I reread the ad and it mentions needing a starter and batteries. Which is not in and of itself that big of a deal I guess, I found a new starter on eBay for $200. But sometimes people will lock up an engine and just say it needs a starter, which can't be proven otherwise until the work is done, at which point you're stuck with a paperweight. I imagine a 3208 is not an engine that can be turned over with a breaker bar.

So, assuming the worst, what are viable replacements for the 3208 that will bolt to the MT643?
You should be able to hand turn it with a large breaker bar.
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Old 07-04-2019, 10:45 PM   #6
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Quote:
Originally Posted by EastCoastCB View Post
Its an all mechanical engine but its heavy and under-powered.
Not the best but they're ok. The internals are small and its a parent bore engine. When they go out its best just to swap for something different.
Seeing how I own one such equipped, I disagree. I can accelerate with the best of them, sometimes out-doing many, Top end is over 80 m.p.h., parts are common, CHEAP, and durable. They are rebuildable. I am very delighted with the performance of the 3208/643 combination. The engine has lots of torque and with the exception of needing a slightly larger transmission cooler, the bus takes on hills and mountains without complaining. It's a solid combination not to be ignored or poo pooed. The engine prefers to be in the higher r.p.m. range where torque peaks (2500 or so). With a fully loaded trailer on the back the drivetrain barely knows it's pulling 5+ tons of stuff. I had to pull over with a fully loaded bus, plus the fully loaded trailer three times climbing from California to Nevada (estimated load was around 29K gross). Try doing that with a 444E OR a 466, let alone a Cummins 5.9L. I'll put my 3208 against them any day, and twice on Sundays.....

M
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Old 07-05-2019, 03:34 AM   #7
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Seeing how I own one such equipped, I disagree. I can accelerate with the best of them, sometimes out-doing many, Top end is over 80 m.p.h., parts are common, CHEAP, and durable. They are rebuildable. I am very delighted with the performance of the 3208/643 combination. The engine has lots of torque and with the exception of needing a slightly larger transmission cooler, the bus takes on hills and mountains without complaining. It's a solid combination not to be ignored or poo pooed. The engine prefers to be in the higher r.p.m. range where torque peaks (2500 or so). With a fully loaded trailer on the back the drivetrain barely knows it's pulling 5+ tons of stuff. I had to pull over with a fully loaded bus, plus the fully loaded trailer three times climbing from California to Nevada (estimated load was around 29K gross). Try doing that with a 444E OR a 466, let alone a Cummins 5.9L. I'll put my 3208 against them any day, and twice on Sundays.....

M
I've got a deal worked out for a 3208 bus, but I'm still not too jazzed about the engine.

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Old 07-05-2019, 11:25 AM   #8
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I get that the 3208 is not a typical Caterpillar. However, consider how much you'll REALLY be driving it...

Speed and such are all subjective in my eyes. When you're used to driving 70-foot, 40-ton vehicles that take 2 miles to reach 65 because they're loaded with 46,000 lbs of freight, you stop worrying about acceleration. Diesels have always had a sort of Achilles heel because they had gobs of torque, but disproportionate on horsepower, even when turbocharged.

But guess what, folks? THAT'S JUST HOW DIESELS ARE. Always have been, always will be. I6, V8, V12, what-have-you. Especially commercial diesels. They were never meant to be in a hurry. Especially school buses, even the gassers could rarely top 60. My previous B700 would do almost 70, but it had a 429 and got around 3 mpg doing it by my calculations.

When you see those Billy-BigRigger supertruckers (those terms are what we professional drivers use to classify morons) screaming down the highway at 75 mph or more, remember a few things...

1) There's likely no freight on the trailer.
2) If there is, it took 10 minutes and 5 gallons of fuel to reach that speed.
3) It's a flying brick, probably getting around 2-3 mpg.
4) Usually, the harder you run a vehicle, the more it's going to break.
5) Couple more zeroes when these break.
6) They have a lot more weight to keep them on the ground.

7) They have a lot more engine with a lot more power.
***13-15-liters, 350-450 avg hp. Some, 18-liter with 500-600 hp***

Last, but not least, they'll need close to a mile to stop, if not more.

I get that for most folks that aren't used to big, heavy vehicles like these, it does seem like a pain in the ass to be limited to 55 mph, or reduced to 25-35 mph on a long hill. But remember, you've got a low-horsepower engine trying to move a 12,000-lb brick. Torque is where diesels shine, and that is what does your pulling. Horsepower is how fast it does it, and you just can't expect much from 175-250 hp with that kind of load. It's like trying to tow a camper with a Yugo. Think about the heavy-haulers that are moving a house. Think about those shorty trucks that move mobile homes. Ever see them going faster than 55? Those may be a lot bigger, but you're moving a house, too, you know.

Diesels can be boosted silly if the setup allows it, but the weak link is your transmission, which likely will not take much more than how it came from the factory. You can re-gear all you want, but you're going to regret it the first long hill you climb afterward. You're driving an old school bus with less than 250 hp and just enough transmission for it, that was built for stop-and-go to pick up schoolchildren, not a 600 hp, 18-speed Kenworth that can top 80 mph.

I probably shouldn't mention this next bit, because as an OTR driver, 99.9% of the time, I ran safe, legal and by the book. Usually set my cruise at 63 and just let it ride, laughing at all the idiots in a hurry to get nowhere. But due to an idiot dispatcher with unrealistic planning and other idiots holding me up for 4-6 hours, combined with the threat of waiting two days without pay to unload if I missed the appointment, I have seen 100+ in a heavy vehicle, 117 downhill to be exact.

BSF (and others) will recognize this as "Georgia Overdrive". To put this in perspective, I moved 44,000 lbs of freight a distance of 1,650 miles in just about 22 hours of drive time. That's averaging 75 mph in a truck that was governed at 65. Across every hill between Omaha, NE and Fremont, CA.

With no traffic in sight and a clear view about 1-2 miles down the road to the next hill, mind you -- I would NEVER do that under any other circumstances. Don't plan to do it again, either. Because I can tell you, these things get a bit challenging at 80 mph, and downright scary at 100. Not to mention commercial tires are not usually rated for such speeds, if at all. Even with air-ride, the faster you're going, the more it beats you silly, and more chance of losing control from a bump in the road.

Bottom line, folks, if you want more speed and power from these things, you'd better start scavenging heavy truck and RV boneyards for a wreck with something more suitable to that purpose. If you're already down with serious engine problems anyway and replacing with OEM isn't cost-effective, have at it.

But I promise you, you'll see how overrated it is when you see the true cost of the swap, especially when you start burning that much more fuel. Mostly because, well, let's face it, very few of us will ever drive our skoolies enough to justify it. Be happy with what you have. It was never going to be a speed demon. Okay, I'll get off my soapbox now.

But personally, I think I'd rather trade speed for reliability, just my preference.
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Old 07-05-2019, 03:55 PM   #9
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Quote:
Originally Posted by CHEESE_WAGON View Post
I get that the 3208 is not a typical Caterpillar. However, consider how much you'll REALLY be driving it...

Speed and such are all subjective in my eyes. When you're used to driving 70-foot, 40-ton vehicles that take 2 miles to reach 65 because they're loaded with 46,000 lbs of freight, you stop worrying about acceleration. Diesels have always had a sort of Achilles heel because they had gobs of torque, but disproportionate on horsepower, even when turbocharged.

But guess what, folks? THAT'S JUST HOW DIESELS ARE. Always have been, always will be. I6, V8, V12, what-have-you. Especially commercial diesels. They were never meant to be in a hurry. Especially school buses, even the gassers could rarely top 60. My previous B700 would do almost 70, but it had a 429 and got around 3 mpg doing it by my calculations.

When you see those Billy-BigRigger supertruckers (those terms are what we professional drivers use to classify morons) screaming down the highway at 75 mph or more, remember a few things...

1) There's likely no freight on the trailer.
2) If there is, it took 10 minutes and 5 gallons of fuel to reach that speed.
3) It's a flying brick, probably getting around 2-3 mpg.
4) Usually, the harder you run a vehicle, the more it's going to break.
5) Couple more zeroes when these break.
6) They have a lot more weight to keep them on the ground.

7) They have a lot more engine with a lot more power.
***13-15-liters, 350-450 avg hp. Some, 18-liter with 500-600 hp***

Last, but not least, they'll need close to a mile to stop, if not more.

I get that for most folks that aren't used to big, heavy vehicles like these, it does seem like a pain in the ass to be limited to 55 mph, or reduced to 25-35 mph on a long hill. But remember, you've got a low-horsepower engine trying to move a 12,000-lb brick. Torque is where diesels shine, and that is what does your pulling. Horsepower is how fast it does it, and you just can't expect much from 175-250 hp with that kind of load. It's like trying to tow a camper with a Yugo. Think about the heavy-haulers that are moving a house. Think about those shorty trucks that move mobile homes. Ever see them going faster than 55? Those may be a lot bigger, but you're moving a house, too, you know.

Diesels can be boosted silly if the setup allows it, but the weak link is your transmission, which likely will not take much more than how it came from the factory. You can re-gear all you want, but you're going to regret it the first long hill you climb afterward. You're driving an old school bus with less than 250 hp and just enough transmission for it, that was built for stop-and-go to pick up schoolchildren, not a 600 hp, 18-speed Kenworth that can top 80 mph.

I probably shouldn't mention this next bit, because as an OTR driver, 99.9% of the time, I ran safe, legal and by the book. Usually set my cruise at 63 and just let it ride, laughing at all the idiots in a hurry to get nowhere. But due to an idiot dispatcher with unrealistic planning and other idiots holding me up for 4-6 hours, combined with the threat of waiting two days without pay to unload if I missed the appointment, I have seen 100+ in a heavy vehicle, 117 downhill to be exact.

BSF (and others) will recognize this as "Georgia Overdrive". To put this in perspective, I moved 44,000 lbs of freight a distance of 1,650 miles in just about 22 hours of drive time. That's averaging 75 mph in a truck that was governed at 65. Across every hill between Omaha, NE and Fremont, CA.

With no traffic in sight and a clear view about 1-2 miles down the road to the next hill, mind you -- I would NEVER do that under any other circumstances. Don't plan to do it again, either. Because I can tell you, these things get a bit challenging at 80 mph, and downright scary at 100. Not to mention commercial tires are not usually rated for such speeds, if at all. Even with air-ride, the faster you're going, the more it beats you silly, and more chance of losing control from a bump in the road.

Bottom line, folks, if you want more speed and power from these things, you'd better start scavenging heavy truck and RV boneyards for a wreck with something more suitable to that purpose. If you're already down with serious engine problems anyway and replacing with OEM isn't cost-effective, have at it.

But I promise you, you'll see how overrated it is when you see the true cost of the swap, especially when you start burning that much more fuel. Mostly because, well, let's face it, very few of us will ever drive our skoolies enough to justify it. Be happy with what you have. It was never going to be a speed demon. Okay, I'll get off my soapbox now.

But personally, I think I'd rather trade speed for reliability, just my preference.
From one "Hand" to another, I concur. First truck I owned was a seven speed 250 HP Cornbinder cab-over with a 30 inch sleeper, and topped out at 62 m.p.h. Solid little semi. Never failed me even in the worst Chicago winters. Always started, never complained. Wish I never let go of her now....

But spot on with your observations IMHO.

M
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Old 07-05-2019, 04:49 PM   #10
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It would be important to know if it's a turbo'd 3208 or not. You can't add a turbo to a natural aspirated 3208 unless you want to waste money. A turbo would be really nice if running in higher elevations.
My non-turbo'd 3208 pushes my bus 70 mph + on the flat and level. Over time I have come to appreciated this engine. Especially when I read the stories about dealing with newer engines, and their expenses.
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