4BT vs OM617 (2 Viewers)

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xunogil

xunogil

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Sep 26, 2012
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Fort Collins, CO
Alright, so I had posted a little while ago trying to get some idea about a 4BT build but now I'm starting to wonder something else and since that thread kind of died I figured I'd start a new one.
So here is what I am wondering now:
I'm still planing to do a diesel FJ40 build but now I am wondering what y'all think would be the better motor. 4BT or OM617
I own a 85 300CD so am familiar with the OM617 and I would use a later turbo model. The FJ would not be for extreme uses mostly daily driving, trips, camping with a little off roading but nothing requiring crazy amounts of torque and such but it would be nice to be able to tow a light something or other with it.

So I wan opinions but also backed stats on why you would prefer one over the other, things I have in mind would be fuel economy, ease of install (4bt needs a spring over conversion) idk about the Mercedes but I would like to keep it somewhat stock looking so spring over conversion is a negative for the 4bt in my book.
Anyways, I hope you have an idea of what I'm looking for so let the battle begin...
 
Merk Swap

Yes he does have Diesel Mercedes adapters to accommodate many transmissions and many Diesel Mercedes engines ;)
 
I like both engines but if you want a more civilized engine the OM617 is the way to go. I did a 5 speed swap but with 3.73 gears and the 5K reving of the Om617 you really don't need it. Much less shake, much less noise and a little less weight. no need for a spring over. Not really the same power potential though. Look below and you know my vote.
 
I'm doing a OM617/NV4500/Orion 4:1 swap right now. Luke's adapters are t*ts. Everything is precision machined and the only think I've had to do that wasn't bolt on was offset dowel pins for the bellhousing (which is hardly a fault to Luke's kit).

The only think I'm having to think out is my motor mounts, but it's actually not that big of a deal. I just want them to be right the first time.

The 617 may not be a powerhouse, but it's cheap and reliable.
 
Turbo a 3B... No adaptors required (just need the diesel input trans shaft), easy to find, bullet proof.:D
 
I also vote for the om617 and plan on re-powering my 40 with one in the near future. 4x4 labs does look like the way to go, just will suck paying more for the trans adapter than the engine.

You will need a lift to clear the front sump oil pan of the om617- I think around 5 inches, but if your not gonna do any hardcore offroading you might get away with a couple inch spring lift and extended bumpstops.

4bt is loud and heavy I think would get old after a while.

om617 is very robust and reliable (as you know) and as a fellow Mercedes driver (79 240D) you know that engine would be the bees knees with a stick shift behind it in a fj40.

om617 is one of the best engines to run WVO. Indirect injected with a bulletproof mechanical IP
 
The OM617 is 125 hp/180 lb·ft and you can get parts for it anywhere, the 3B is 90 hp/159 lb·ft 3B you can't get parts for it at all in the states ... this just makes no sense to me. Motor mounts have been solved:

http://www.mercedesdiesel4x4.com/product_p/a-mb106.htm

You don't have to run any lift, you do have to notch the oil pan ;)

Tucker

PS: Don't get me wrong, I think Toyota makes great diesels. I also know it takes 6 weeks to get a head from England when that bullet proof engine blows a headgasket :-(
 
Last edited:
Wow I have to say I am surprised...
I was expecting much more support for the 4BT, but everything that you all are saying is making sense, here I thought it was set on the 4BT but now I am heavily considering the Mercedes...
 
overpaid slacker said:
for what it's worth, I am running SUA with a 4" spring lift on my 76 fj40 4BT.
I prefer the 4BT for the endless performance mods. just my $.02
Click to expand...


IIRC the 4BT, while being a great motor, is notoriously loud.
How's the noise at highway speeds for 5-6 hours at a time?
 
tucker74 said:
It's all about dampening the vibration, the stock Cummins mounts most go with are the soft liquid filled mounts ...

Tucker
Click to expand...

There is a huge difference between the construction of these MBZ and Cummins motor mounts. Apples to oranges. However, I completely agree that the name of the game is vibration dampening.
 
There has been at least one positive result from balancing 4BT rotational parts. A local place said they did one and it made a huge difference.

I am still waiting on my OM617 to get back from a shop, but that is the direction I'd go (mine is for a mini, so apples to oranges). The 4BT has more grunt, the 617 was built for the street and a bit more revs. I agree the 4BT probably has more build potential (at least there is evidence of people doing that more often). Like mentioned, the key is livability. There are a LOT of 4BT swaps for sale from time to time. I don't see as many OEM diesel swaps or 617 swaps for sale.

You get good options in the lighter 40. For a 60 that had bumper/slider protection and loaded for trips I'd only do 6-cylinders or more. Depending on what you tow you might want to consider more cylinders as well. A 12H-T would be a fun swap into a 40 (friend has done them), or an HD-T. I would probably not do an HZ-T for towing duty, but on a 40 it could work. You will likely stress a 617 depending on what you're towing.

What you should look for is an OM642. ;) I have been wanting to attempt one of those badly.
 
Hmm I might like the idea of the OM642 but it has not been around long enough to be able to attest to its reliability and durability. I want to go with a tried and true motor.

Thanks for all the input, and keep them coming if there is more, I want to hear more. The 40 will be used more as nice cruiser and some light off roading, nice long trips mostly on paved road have to be reasonably comfortable. It would be great if towing was an option with it, but there is a 7.3 powerstroke that is around for most towing needs, but if a trip comes up where the 40 wants to be used, it would be nice to be able to tow something small with it, but I don't need it to be a big tower.
 
Oh man, why do people have to keep posting things like this, first I though I was set on the 4bt, then I though I was set on the OM617 and now....
that post just got me started doing some research on the OM606, In line 6 cyl diesel? hmm tempting, can anyone tell me more of what they know about this motor while I'm researching on the side?
 
WTF?

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