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I'm thinking about a diesel stovebolt and have found quite a few P30s with the Cummins BT4 but they all have around 100k miles. What sort of life can you expect out of these engines and around how much does an overhaul kit run for one? ( I googled and couldn't seem to find any )

300,000 miles is not unusual for a diesel.
Got any pics or links to look at one? Are they really stovebolt-derived? What's the displacement?

Here's a picture of one.
http://photos.thedieselstop.com/showphoto.php?photo=17723&papass=&sort=1&thecat=

They are 3.9L and I guess the same basic engine as the 5.9 but with two less cylinders.

They aren't stovebolt derived but they are in GM parcel vans with GM transmissions.

Depends on use of course, but the 300K figure earlier is a good estimate. More stop and go, lower mileage but if on longer trips 500K is possible. As far as parts cost go, LOTS. Check some motor rebuilders for replacement cost, and compare to gas engines. That will give you an idea of the diesel parts premium.
I replaced the sleeves, pistons, rings. seals and gaskets in a similar 4 cyl Mitsubishi truck recently. $2000 in parts and machine work. Note, that did not include any crank or bearing work.

Check out Cummins-Conversion.com

I was thinking of that also, it should cost about 1500$ to rebuild one if you need no machine work. You had better know what you are doing since you don't want to mess up a good motor. I figured with an OD trans, you could get near 25-27mpg. They should go 250k miles EASY.

I think 300000 miles is on the low side. I know this is the same as the 5.9 with 2 fewer cylinders. They will easily run 10000 hours if maintained. I have heard of one with 21000 hours without being overhauled. I don't think the parts are too expensive either, I would think you could buy an overhaul kit for 7-800 dollars but of course a valve job would be on top of that. You would also want to go through the injectors, not terribly expensive but definitely another expense. They are a great little engine.

I used to do work for a fleet of step vans that used a lot of these engines. They are rugged but are slugish & vibrate a lot.

The 4BT Cummins is a great engine except for vibration. They do not use an internal balance shaft like the 4045D or 4045T John Deere. This balance shaft makes a lot of difference. We have several of these engines around my trade area and without exception all the instument panels and accessory brackets are all broke to pieces on the Cummins after 2000 hours, but the Deere panels and brackets are like new.

For what it's worth, I was talking to a fellow ATHS member who has but a 4BT into his daughter's '48 1-ton. He said with the GM bell housing and flywheel, it was a bolt up to his SM420, rear engine mounts and rear axle -- all he had to do was slightly modify the front cross member to accept the lower front engine mount on the Cummins. He reports that the truck can easily cruise at 62 MPH.

I'll have to ask him about the vibration.

r,
John

I got a call from the same fellow with the 1 ton with 4BT. He is looking for a pair of long running boards.

I asked a few questions about the conversion.
I think he is stil using the same rear, I am sure a 3.54 or faster rear would help it considerably on the speed, noise, vibration, and fuel mileage.
He also said that he bought the engine new from cummins for around 4,000 a few years ago. He has also done a Diamond T with the same engine, I have seen that one at shows, however he no longer owns it.

Grigg