4bt or 6bt cummins

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Dec 16, 2005
Hey all,

I wanted to get some opinions on diesel conversions as far as 6bt vs. 4bt Cummins .First of all I have a 85' FJ60 that I want to convert and was pretty much set to get started with a 6bt which I already have the donor truck a 91' Dodge 2wd with 727 trans. when I had an offer from someone willing to swap me a 4bt with a TH400 trans. Since I have"nt got started yet I'm wondering which route would be the way to go for my intended purpose for the sixty.
- Second vehicle/Pleasure vehicle
- Occasional offroading fun
- Trailer dragger(14' enclosed with up to 4 dirtbikes,gear and riders 70mph)
Now that I have both options available it's down to choosing what would work best for what I would like to do.Any advice here?
I have a 4BT in my 60 and absolutely love it. In my honest opinion, a 4BT is plenty powerful enough. A 6BT is way too powerful for a 60 and this power would be unused. And, if you really stepped on it, I bet things would break.
As you might know, the 4BT can be turned up for more horses and more torque but losing a little fuel economy.
I don't know about pulling your trailer. I think you would be asking a lot to pull a very heavy trailer with your 60. 60's are not really designed to pull a big trailer. I can pull a 18ft trailer with a car on it with my 4BT FJ60. The motor would definitely pull it at 70mph, but the 60 will not. It is quite dangerous and very scary. I pulled it at slow speeds, maybe 55-60 max.
My advice to you is not to try and make a 1/2 ton SUV into a 1 ton truck. The 6BT is too much and you would not get full use out of it anyway. If you want a heavy hauler, buy a 3/4 or 1 ton pickup. Don't use a 60.
I had the same intention that you did. I wanted a 60 with good fuel economy and that could pull a good sized trailer. I thought the 4BT was it and it is, but the 60 isn't..
Hope that helps.
Thanks for the advice.I think the chasis will handle what I want haul,my load is probably about half the weight your hauling I just did'nt want to be running the engine at the high end of it's capabilities for hours to get to our destination which was the case with the 2f and horrible fuel mileage.I've been leaning more towards the 4bt now that I've done some more research I just got a great deal on The 6bt at the time but I think I'm going to go ahead and swap for the 4bt.Thanks again for the advice
So does that mean that you are getting rid of the 91 Dodge? :grinpimp:

Just (almost) kidding.

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