anything have a Cummins 4BT?

[nearhomeless]

The P30 chassis for things like bread vans and such often had the Cummins 4BT in there, i'm wondering whether any skoolies have, now that I see that chassis was also used for school busses...

It seems like a very good engine, getting very good mileage..

[the_experience03]

And it will shake you violently the whole way. I've never seen a bus with a 4BT, but I've only seen a handful built on the P30 chassis too. The ones I've seen on the P30 chassis were all gassers. I'd love to get my hands on a 4BT, but $$$

[Hearse Driver]

I also have a P30, and the 4BT is one of the engines I have been looking into to replace the 350 gasser in my bus. I saw a listing on Ebay once where a step van had been fitted with a 4BT, but I've never seen one in a P30 as of yet.

Something I was wondering about is how good the 6.5 is. From everything I've heard, the 6.2 was a better boat anchor than an engine, but I really haven't heard much about the 6.5. One cool thing about the 6.5 is that it wouldn't require any $1000 adapter kit to hook up to the 4L80 like a Cummins would. It's pretty much a direct bolt-in. But then a new computer would have to be bought...

From a conversion site that I've been doing some of my research on and what I've heard from various people, the earlier Dodge auto trannies should be avoided like the plague, so if I went with the Cummins I would either have to shell out for a different tranny or stay with the 4L80 and buy an adapter and a new computer.

So I suppose my question would be as to whether the Cummins (either 4BT or 6BT) is so much better in mileage and performance than a 6.5 that it would justify the extra cost of the conversion.

Besides the engine/tranny costs, then I would also have to put new gears in the axle.

Any theories?

[Jarlaxle]

There is a FACTORY adaptor to put a 4BT in front of a TH-400, it will work for a 4BT or a 6BT/4L80E. HOWEVER, the 4L80E then REQUIRES standalone computer control, which isn't cheap. Some bread trucks had 4BT's and TH400's. J. J. Nissen/Wonder Bread also had a bunch of Ford-chassis stepvans with 4BT's and 4-speed manuals.

Something I was wondering about is how good the 6.5 is.

It's a catastrophe, managing to combine the mileage of a gas 350, the power of a lawnmower, and the reliability of a Yugo in a demolition derby. You're better off with a gas V6. The last all-mechanical 6.5 turbos are the best (1993-4, IIRC), but that's like saying the EFI 5-speed GVX is the best of the Yugos.

So I suppose my question would be as to whether the Cummins (either 4BT or 6BT) is so much better in mileage and performance than a 6.5 that it would justify the extra cost of the conversion.

ABSOLUTELY YES! I wouldn't own a 6.5 if you gave it to me.

Personally, I'd just keep the TBI 350.

Dodge's 48RE can be built to handle any power level you want...I watched a Ram 2500 with a 24V Cummins put down 1200HP and 2500+lb/ft (still climbing when it pegged the dyno) through a 48RE. The truck was then driven about 3500 miles. It had over 120,000 miles on it, an untouched bottom end, and was the owner's only vehicle (and a low 11-second truck in the 1/4 mile). Some racers even run built 48RE's behind cranked up Duramax diesels.

[the_experience03]

As Jaraxle stated, there is a factory adapter. There is also a factory transmission controller, but they aren;'t easy to find. Early 6.5 trucks will have them as well as military humvees. It requires input from a VSS which should already be on the trans, a tach input, and a throttle position sensor. The TPS is the only one that might be a little tricky to hook up, but it wouldn't be terrible. A cheaper, easier option in the long run would likely be a TH-400 with a Gear Vendors overdrive which won't require any additional electronics and will actually give you 6 speeds including one overdrive. Of course, you still won't have converter lock up. I suppose a built TH-350C could be used giving you converter lockup.

[Jarlaxle]

I see two possibilities there...

One is running a built TH-700 or 4L60E, which gives you OD, lockup TC, and a 3.06 first gear. It will work with the TH-400 adapter, though a torque converter might be tough to find.

Another that seems to be the easiest (at least regarding engine-trans atattchment) would be running a Chrysler trans, either an older A-618 or the newer 48RE.

A third solution would be an Allison automatic...IIRC, the Cummins has one of the standard SAE bell patterns and will bolt to any AT or MT-series Allison with the right bellhousing.

[nearhomeless]

Just sharing what i've read elsewhere like at 4btswaps.com forums...

The 4BT is like 2/3 of the common Cummins 5.9 as in the dodge trucks, otherwise the same engine.

Mileage is exceptional - swapped into a 3/4 ton 4x4 suburban expect 26-29mpg. One person with a 1 ton 2wd van reported 30mpg. The big P30 box vans apparently get 15-19mpg. Is apparently plenty of engine even for a 1 ton if modified a bit, the 5.9 cummins is alot heavier and overkill and harder to work on, it's only real advantage is being smoother.

Power can be substantial with upgrades. Stock is only 105-130hp range but 300-400lb/ft of torque. Modified versions have pushed over 500hp (yes really) and 1200lb/ft of torque, with things like 75psi boost from compound turbos. O_o Seems like a great engine for short busses, hence my interest. Even stock fairly easy to turn up power a bit, add DIY propane injection and such. Sounds like reaching 200hp should be almost no big deal at all, making it comparable to other diesels.

They vibrate like HELL and are real noisy. But again, P30 is a factory setup so...

Weight is about that of a big block chevy - 680-750lbs wet or so.

They commonly came in some UPS step vans, most Frito Lay and some bread vans, in the P30 chassis - often mated to a TH400 sometimes to a manual like an SM465. They had enough torque that early TH400 death is one reason for early sales of the vans.(!) They had a special bolthousing to bolt to the TH400 which apparently also works with a 4L80? I'm told they kill most of the GM automatics though stock from the factory with near 400lb/ft and needing to lug constantly. One of the 4 speeds is specifically NOT recommended due to some weird harmonic issue even if built for the torque, possibly the 4L80 or 4L60.

So you can see the reason for my interest - pulling 20+ mpg in a short bus would make it like a poor man's Sprinter with even more room. I'm just wondering if they came in anything ELSE.


As to the 6.5 engines they are smoother than the 4BT but apparently the turbo version has some durability issues or something. I'm told the Duramax 6600 is a real good engine - can also be hot rodded while keeping the mileage, but still wont match a 4BT in mileage under the same load. Basically nothing will except the 6cyl Cummins when youre pushing something like a long heavy medium duty when the 4cyl spends all its time at high load.

Expensive options like Gear Vendors anything definately not what i'm looking for - the used bread vans often sell for $2500-3500 and the aluminum bodies go to scrappers for $750-2000 depending on area and such so picking up a working engine for $1000-2000 should be fully feasible, as should the trans bellhousing. Better condition (ie good trans) or fixable ones might make a good conversion even if it's not a skoolie alternately. Veggie oil conversions apparently work fine.

[nearhomeless]

Oh and obviously dodge trannies are an easy bolt up because the 6BT in the dodges is just a longer version - something like a dodge automatic or an NV4500 stick (my preferred option if I did it), both designed for 6cyl torque and only having a 4cyl shouldn't have a problem.

[Jarlaxle]

Be aware: most GM bread trucks aren't 4BT's. There are thousands out there with 6.2 and 6.5 Detroits, including a massive number Penske leases to Entenmann's. Many Frito-Lay trucks aren't even GM anymore--the new ones I see lately are all Ford chassis with gas engines. Most older ones are gas 350's.

Your best bet might be an owner-op with an old truck...Peppridge Farm guys own their trucks, Snyders, Wise & Bachman-Utz drivers frequently do also. I see them in all sorts of oddball stuff...a guy in northern Mass still runs a 1976 (!) Ford. It's a single rear wheel Stepvan with a Grumman body, very obviously a former Sunbeam bread truck (it's still very-faded faded blue & yellow with white paint over the Sunbeam logos)...he paid $900 for it and figured he'd be happy if he could get a year or two out of it. That was about nine years (and 150,000+ miles) ago. It has a gas 300 inline six (what else?), a 3 speed ON THE COLUMN, no power steering, and no power brakes. He figures it has close to 400,000 miles by now...and it still starts instantly in sub-zero weather. Another guy delivers Snyders pretzels in an old Snap-On truck.