A different Cummins question

[Chris Olson]

I have seen the Cummins 4bt pictures on Cabell Garbee's site.. the 4bt seems to be a proven Swap.

My Question is ...has anyone successfully done a 6bt swap on an M37?..

I am Just wondering If anyone out there has a link to some pictures ..

Either pictures of a clean install or a nightmare hack job would be appreciated

Thanks. Chris

[CGarbee]

Actually, there are a couple of photos on my site of M37's with the B5.9... You have to move the radiator forward, or push the firewall back, or a combination of both since the engine is about 12" or so longer than the B3.9 (4BT)...

One of the trucks (Don Beckwith's) is truly outstanding, but he has done enough modifications to the truck that it looks more like a baby Kennworth than a M37 IMHO, so you might not have recognized it in the photos... The other one is from a fellow in either WV or Kentucky (I forget) and the shots are of the truck in progress. It also is a great fabrication job, but the truck itself is not quite as tricked out (yet).

Keep in mind that there is a lot more weight on the front end ...

You can turn up the 4BT a lot (to where you really will have to worry about the driveline) so I think it is the better option, but it is possible to stuff in a 6BT if you havet he inclination.

Bug me if you can't find the 6BT photos and I'll post the links. (I've got to head out for a meeting or I'd dig them up for you...).

Thanks for mentioning my site and rig...

[derek]

I'm intrested in the same converion. is there some other picks or a link of a finished product with the 6tb swap. i would of thought more people would have tried this swap. here is the link to Mr Garbees site with a fellow doing a 6tb.


http://www.garbee.net/~cabell/photos26.htm


i wounder how he is doing. i tried to email him but it did not go through. OOOO... Mr Garbee, Beautiful site! you are booked marked in my favs.

[HWooldridge]

I had always heard the 6 was bordering on too much weight for the M37. It could be done if you had a free engine laying around but the 4 was a better fit for a lot of reasons. Maybe Charles can offer an opinion.

[Charles Talbert]

6BT or 6BTA in M37

Sure it can be done, if a client requested it, I'd get right on it. There are pros & cons of course. A 4 BTA has been my choice because it supplies plenty of power & torque, also allows room for the longer 5-speed over-drive trans. without major modifications. A 4BTA coupled with the correct gearing for its torque range specs. will give better fuel milage than a 6 cylinder all day long, a major factor with today's fuel cost. Its just a good set-up to work with, in turn keeps cost lower, doesn't destroy the integrity of the vehicle in any way in the event someone wanted to go back original in the future. We can install a jet engine if somebody wants it, but why throw extra time & money at a project when it really doesn't need it, what real purpose will it serve? Another thing you must think about is that these trucks are designed with a certain power range in mind, more power & torque can cause a lot of problems in the drive train if not handled properly. I think most will admit, if more power is available, it seems one just can't resist punching that accelerator a little harder. How far does one push the envelope?

[JimmieD]

What kind of power can one reasonably get from the 4BT? C Garbee makes the reference to turning it up, so what are we looking at stock, and then at middle range of performance improvements, and then at a higher end? I've been considering this engine for another project but haven't gotten a lot of info yet.

JimmieD

[CGarbee]

The 4BT that I have (1990 Recon, turbo with no aftercooler) is rated at 105hp and 286lb-ft. The most current version of the engine is the ISB3.9-175 producing 175hp and 420lb-ft.

A very common version of the engine that can be found pretty easily in take out form from things like bread vans is the 4BTA (early to mid 1990's) rated at 125hp and 320lb-ft. It is bassically the same engine that I am running but with an aftercooler added.

Since the 4BT/BTA B3.9-xx ISB3.9-xx are all smaller but bassically the same engines as the comparable six cylinder versions found in the RAM trucks (among other uses), you can use the same tune up kits offered for a given year/model and use a portion of the parts. You can expect about 2/3 the increase in hp/torque that any of the kits offers for the six cylinder...

Piers Diesel is a great source of info/parts for turning up the Cummins.

Just a note though, I can comfortable haul a loaded M101 trailer behind my loaded M37 (figure it at around 12,000lbs total) without problems on the highway. I do slow down a tad going up hills when loaded like this, but my point is that I can work my truck pretty hard without having so much under the hood that I worry about tearing up something in the driveline...

[HWooldridge]

Cabell,

What do you achieve for top speed and typical mileage with your conversion? I'm talking about whatever is normal and comfortable. My stock M37 will go 55 but I don't push it that fast. I did it once just to see if it could get there and don't plan to repeat the stunt but the truck will comfortably go 45 all day long.

[JimmieD]

Thanks Cabell!

I'm tossing and turning trying to figure the BEST mods to a non-M37 as a final buildup for the long haul. I'll post in another thread so as not to sidetrack this one.

JimmieD

[Charles Talbert]

Cummins 4BTA

Originally posted by JimmieD
What kind of power can one reasonably get from the 4BT? C Garbee makes the reference to turning it up, so what are we looking at stock, and then at middle range of performance improvements, and then at a higher end? I've been considering this engine for another project but haven't gotten a lot of info yet.

JimmieD

The new Cummins engine I use for repower is a 4 cylinder, turboed, aftercooled, version putting out 130HP stock. I haven't turned one to see just how much it would do as far as additional power being available. Turning up the fuel will void the warranty on a new engine, therefore I can't go that route. The peak torque range is at 1,600 RPM. You can feel it start to kick in strong at around 1,450 RPM. 55 MPH is achieved at 2,000 RPM the way I set mine up. This is a very good cruise range. I would love to repower one with the ISB engine, however they have not been made available through Cummins for sale to the general public at this time, they are all going to manufacturers such as Freightliner.

[CGarbee]

Charles is right about availability of the newer engines... I just keep looking hard each time I see a newer delivery van on a Freightliner Custom Chasis to see if it has a newer engine that I can snag whenever I pass a wreck...

About performance... I am currently running with a ZF S5-42 transmission (0.76:1 fifth gear) with 4.89 gears, 900r16 Michelin XZL tires, and the stock transfer case. Truck has a hard cab and manual front hubs (Superwinch). I run at 77mph with the pedal firmly planted on the floor when everything has gotten good and hot. I don't like to drive this way. My usual Interstate cruise is at 70mph when I get 15mpg. I average 14-15mpg when I use it as a commuter truck (20 miles to the office, evenly split between two lane country road, interstate loop, and city stop and roll), taking trash to the dump, etc. Best I've managed (on many trips) is 17mpg when running at 50-55mph with a M101 trailer hitched up with both the truck and trailer moderately loaded.

[tonkadoctor]

Big Motor = Broken Parts

The most current version of the engine is the ISB3.9-175 producing 175hp and 420lb-ft.

That's more than double the rating of the flathead six, and nearly the same as the older 6BT.......somethings gonna give here.