I think it is mostly the length... the 4BT is just easier to fit in compact bays.

 

Ya it's the length for sure. I know with a 6bt you would have definite firewall modification. Plus a 4bt set up properly would have more than enough giddy up.

 

Yea, but I think it was in the link AK posted that the guy wished he wouldn't of wasted the time with 4bt and went with a 6bt instead. That isn't the first time I heard that. I wondered what the main reason was for the swap in general.

 

Do they put out some killer torque, speed or both?

 

The specs are actually not very impressive. They only have like 110 horsepower and under 300 lb ft of torque. They are VERY reliable.

 

Here's some specs on it:

http://www.cumminshub.com/4bt.html

And 6BT sepcs:

http://www.cumminshub.com/12v.html

The 6BT is 10 inches longer.

 

That's what I was wondering, better mpgs w/4bt. 16 I believe. Not great but better. I done 16 and a little better on ocasion, but it doesn't last lol.

 

They can be built to make some pretty serious power. Single turbo, twin turbo the sky is the limit relatively. A 6bt obviously can be built higher, but who's swapping a diesel to race or tow over rated weight.

 

Not I, but I'm all about making it easier to do what's expected. A little extra gitty up, - I sure I would suffer that well. Hell, I'll fess up, I want it just for that whistle

 

I hear you, if I was going to dump 10k into a new engine, I would start with a fresh 5.4, built bottom end and 2 small turbos like the ecoboost trucks have. It would pull like an absolute train, massive torque probably around 500-600. That would be fun IMO.