Starting a 4bt swap

[JimmieD]

Yes, later turbos will fit but most had a different exhaust angle. When you're doing a conversion that doesn't have to be a problem cause you can do anthing you want with the exhaust within reason. Stock they come with a Holset H1C, and I've heard some were wastegated. I believe the next later is the Holset HY35 which isn't much more than a hopped up & wastegated H1C. Later still the HX35 was used and it's a lot of turbo.

Other options are to go with aftermarket turbo or upgrades to the stocker. That's what I chose to do: HTT [High Tech Turbo] Stage II on a 4BT is roughly equivalent to a Stage IV on a 6BT. 4BT H1C usually has the 16cm exhaust housing which is an upgrade over the housing used on many 6BT's measuring 18, 19 or 21cm, so that and the stage II compressor housing and wheel ugrade results in a turbo very similar to a Stage IV.

Can't say yet what it will do cause it's not installed yet. One of the main benefits is to lower EGT's [exhaust gas temrperatures] when towing or running hard. Along with that it will have better spooling characteristics and a wider powerband when combined with some other free tweaks.

[Keith in CO]

4bt in an M715

Sounds a lot like http://web.mac.com/ltalessi/iWeb/MV/m715.html

The stock t-case should be a divorced NP200, and you could set it up divorced to the TH400. To keep things short, use a 2wd 4" tailshaft and housing if the TH400 from the Frito truck didn't come that way.

[CGarbee]

I'm looking at a pair of 4BT Cummins/GM stepvan engine mounts here and it looks like it tilts toward the passenger side. Can't remember why though....?

GM application stepvans (P30 chasis): Engine tilt is ten degrees to the passenger side for valve cover clearance of the hood. Transmission sits level (twist is accomplished by offset of the front engine mounts and by the flywheel adapter). Twist would actually be usefull in a M37 or PW conversion as it helps in providing oil pan clearance of the front differential (since it moves the pan toward the driver's side).

Remember that the Cummins 4BT in a Chevy or Ford routevan (stepvan, breadtruck, etc.) is a repower. In a Freightliner chasis, it was OEM (now it is an optional engine as the stock engine is a Mercedes unit...) backed by an Allison auto.

Hope this helps :)

[yosemitesamiam]

It sounds obvious this guy would like to end up with a high performance pulling vehicle since he's going to the trouble to install axles this heavy along with the other changes from stock. It's pretty easy to overwhelm the engine capability with a set up like this, tall tires & all. After doing a good many repowers & having some experience under my belt, I personally wouldn't recommend less than a 6BTA in the application. The fact that he intends to use an automatic transmission is certainly a factor as that set up won't perform well at all if under powered.

Gordon, you ask about the 4BT in a stock truck. I would recommend a 4BTA in that application simply because there is more lead way to work with tweaking out more power with an aftercooler in place. I have used a 4BTA in a 715 that worked out great. It was a driver capable of 70 MPH. The 4BT is OK if it suits the owner. I just like having all avenues open if I'm going to the trouble & expense to do a diesel repower. This is why we install the 4BTA's instead. I have nothing against the 4BT, I'd install one in a minute if someone asked us too.

Hey, question for you Cummins repower guys. Is there a break down of what vehicles the 6BT will only fit in, and another list of only 4BT capable trucks/carryalls, etc.???

For instance, if I had a dream of grandeur, and wanted a 6BT Power Wagon, would it fit in a mid 50s Civilian PW? Has anyone tried it successfully or unsuccessfully?

Thanks

Sam

[mcinfantry]

call me if i can help.

lee alessi
225 445 6223
4.56 gears, and a 4bt, not after/intercooled stock fuel setup

http://homepage.mac.com/ltalessi/iMovieTheater124.html

[Safaritow]

Pics of the swap

We drove him in and had it out in 2 hours, It was still warm when we set it on the floor.

[Safaritow]

More pics

Was easy getting it out the door

[Safaritow]

more pics

On his way to a new home.

[DeLoit]

Is the engine bay in a M37 as big as a M715?
I'm was looking at a 4BTA for my M37. I'll be using 52" XML's and Mog U1300 axles. Sounds like I need a 6BTA, or a modified 4BTA. Any thoughts???

[mcinfantry]

Is the engine bay in a M37 as big as a M715?
I'm was looking at a 4BTA for my M37. I'll be using 52" XML's and Mog U1300 axles. Sounds like I need a 6BTA, or a modified 4BTA. Any thoughts???

wow. i dont think a 6bt can fit in an unmolested m37

[JimmieD]

4BT is plenty for an M37, even more than enough. Good power, excellent mileage, plus you can tweak it up really easily for not much money. Regardless of sheer size, as Lee mentions, who wants the weight of a 6BT on the front end? You'd like the 4Bt, believe me...

[DeLoit]

Thanks. I was going to go the Chevy 502 route until gas prices went up. I think this will be better and cheaper. Also diesel is cheaper in my area. I wish I could use a multi-fuel as in my 5-ton :)

[JimmieD]

I think one of the most important aspects of that or any other conversion is to go the extra mile on research so your final drive ratios are correct. However you do it, if you get the gears in the drivetrain right you can build a winner.

[DeLoit]

Well, my axles are Unimog 1300L's-- gear ratio is 6.52. I have a NV4500, 5th is .73. Already have the 53" tires. Have not decided on which t/c and ratios for that yet. I've gone to far to start over now, both time and money, to get what I have now.

[JimmieD]

Those ratios/tires sound good. Top speed of about 75mph @ 2480 rpm, cruising in 5th @ 60 is 1984, so that's close to the sweet spot for a Cummins 4BT. A 3,200 rpm governor spring in the VE pump will help in the stretch between 3rd gear and 4th gear, but may not be necessary.

Mine has 4.1 gears with 29" tires and NV4500, and I broke the speedo at 82 mph, so it was above redline. They'll twist up a little tighter in 5th on the highway. Mine cruises easily at an indicated 75 mph, which is supposedly 2,850 rpm, with what's supposed to be [?] the correct speedometer gears in tranny. Also it matches the highway speed indicators so it's very close to correct. You shouldn't have any problems there.

http://www.reiderracing.com/rtech_engineRPM.htm