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4bt swaps?

80' 427

80' 427

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So I was reading the BART thread and it got me thinking. I have a 6.2 dually and would like to make it to the BB one of these days. It is turboed but I am a bit afraid of a major failure that would cost a bundle on the way to or from. I will try and push the limits for a few years here but it still scares me. I see bread truck 3.9s all the time on craigslist. Am I silly to think that would be enough for my tow rig? If it would run 65 or so I would be happy. Not overly excited to reinvent the wheel here so the 465 would stay. Am I silly? I have seen 250 hp 500 ftlbs from these engines in the magazines, is that realistic? I just figured the 4bt would fit the best.
 
the 4bt would do best in a NON tow rig for high mpg purposes from what i've read:dunno: thought about this for my burb to use it as a camping trip rig. heard it isnt a speed demon but possible to get mid 20's for mpg.

6bt for towing
 
Someone here did a 6BT with a 465.......I can't remember his name now :doah: had a lot of good info, he was from AZ IIRC. I will think of it ......

It was in a K5
 
His name is Greg. He was a good resource when I did my swap while I lived in az. He swapped a larger input shaft into the 465 and had South Bend make a clutch for it. He didn't really tow much more than a camper, but had no problems with the 465 behind the Cummins. The only real complaint he had was the gear splits. I think his axles were geared at 3.42 with 37" tires. That makes for a good cruiser that sips fuel, but it wasn't ideal fur pulling trailers through the hills.

I pull with my truck mostly in 5th gear. (.73:1) and if I need more grunt 4th gear is 1:1 so that gear split lets me maintain my speed if I have to downshift. Even though I have the governor spring and fueling mods done to the injection pump, the motor really favors the lower rpm's and seems to work the best between 1700-1900 rpm's
 
4BT`s seem to be worth a fortune around here if you can find one.

About how much are those bread trucks going for?
 
3.9 is a common irrigation motor here. I can find the rest of the adapters. I just figured I am replacing a 6.2 so I am not expecting much.
 
I see where they are getting 200-250hp and about 450-490ftlbs. I just figured it would be easiest to swap in since they were already suited for the job. Idk I may just shop for a cheap one and in worst case put it in my K10.
 
This is a relative question and I cant believe no one has asked you what you plan on pulling. This is like asking whether a small block is enough to tow with. Sure a small block is enough to tow a single car trailer with something on it. Is it enough to gooseneck a 3 car wedge, not a chance. Same thing goes with the 4bt vs 6bt.

Honestly you're looking at needing the same gearing as a 6bt. 6bts are 1000lbs dressed, 4bts are just around 700lbs. While Im a huge diesel and 4bt advocate I must admit I have no personal experience with them. There was something about that motor that just always put a smile on my face when I saw it in builds. Theres no reason a 4bt wont pull 10,000lbs given the correct setup and hopped up a little bit with the achievable numbers. Thats nearly in pulling two car range, or a big beefed up full size.

If you plan on regularly pulling 2+ cars or the equivalent then I would go with a 6bt. Either way I wouldnt recommend a sm465 behind the likes. The gear jumps are just too huge to keep a diesel in that sweet spot as already mentioned. You also need to weigh out whether or not the decreased mileage is worth having more power on tap. Research the hurdles to beat the vibrations associated with the 4bt too. Rubber or even hydraulic motor mounts are advised.
 
I guess this is what I think. The truck currently has as 200hp 450ftlb 6.2 in it currently. On the farm it may pull north of 10,000lbs but we are talking 5 miles at 30mph. On the highway it will pull my single car trailer with my k30 or camaro on it. I don't need anything crazy just something that will replace the 6.2. In fact if I could trust the 6.2 I wouldn't even replace it. I just like how a diesel works on the farm. Yes someday it may pull the K30 to moab but that is aways down the road. I would love a nv4500 but they are expensive around here. It may get one or a gear vendors someday but it will just have to be happy running 60mph in direct.
 
I worked on one in a ford crew cab on 37s. I would guess it was probably in the 225/475 range. the power was very surprising, although even with the governor done, power range was very short. Felt worse than a 6bt

I think with lots of gears one could be made to work very good. He said he got 25mpg pretty consistent. He had plans of different engine mounting, the vibration was very bad, I wonder how his new mounts worked out.
 
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