4bt or 6bt swap

kroad83

New member
Hi I was wondering which swap I should do. I was originally thinking about the 4bt Cummins swap but then I herd I could do the 6bt swap so I could have more power. I have a 1981 jeep cj7 5 speed lifted 4" with 35in tires. It currently has the 4.2 straight 6 in it. Could you guys tell me what would be best and what all I should change and how? Thanks a lot for everyone who helps me ahead of time.
 

i think google is the best spot for this information. lots of google.
 
alright..... iv been looking for awhile and most of the ones I look at is people saying how they love the persons jeep. Although I have some info on upgrades or what I could do to it. most people are doing the 4bt swap because of the weight but I need the extra power for the highway I live near and drive that so I was thinking the 6bt. just when I play in the mud im not so sure about the weight unless I can some how make the rear end heavier as well. just need to know what all I need in the swap and everything.
 
The frame would never hold up to the 6bt if it would even fit in the Jeep. I think the easiest way to get a 6bt is to shorten a 3/4t truck chassis and install a Jeep tub.

Stick with the 4bt if you're set on jumping on the diesel wagon.
 

The 6bt is a HUGE motor at 1000+ lbs, 40+ inches long and 38 inches tall. The 4bt is 700-800 pounds at 38 inches tall and 30 inches long.

I would personally love to do the 4bt swap but I can't get past how much it weighs and how much it would throw off the weight distribution while wheeling. I have found a massive amount of information at WWW.4btswaps.com. Look through their forum, read the builds. Again lots of information there for 4bt and other diesel swaps.

Best of luck,

Bacon
 
ok thanks guys. I have found a couple different jeeps with the 6bt swap and it was a tight fit but I liked it. looked good also but then again so did the 4bt. but the 4bt wont get up to speed that fast and driving on the highway I thought about doing. but ill keep looking at the 4bt and also the 6bt. I have thought about plating up my frame or doing the truck frame but not sure if that's what I would want to do.... would be awesome tho. lol
 

Can't you turbo the 4bt? That should give you a little more Getty up for the highway.
 
All of the road application 4bts have a turbo. The 4bt is capable of producing 250-300hp and 450+ torque with modifications. As Bounty said with the correct transmission and axle gearing it will get up and go.

Bacon
 
I am not a big fan of the Cummings engines. They are big and heavy. I think there are MUCH better options in other brands.

Unfortunately for you guys, Diesels are not common in the US, but in the rest of the world, they are as common as gas engines (even more so for 4X4 trucks). If I were to go into a diesel, it would be a Toyota one from their HiLux pickup (you can find parts basically everywhere around here). I
 
What is the Toyota diesel engine called? The Toyota engines (at least gas engines) run for forever. I just thought about the Cummins 4bt bc it being stock has 265pounds of torque which is more then a stock 4.2 liter straight 6 gas engine that is currently in my jeep.
 

The engine is the 1KD-FTV. It is a 3.0L straight-4 D-4D common rail (ultra high pressures of up to 135 mpa (1350 bar or about 19,580 psi) diesel engine with a variable geometry turbocharger and Intercooler. It has 16 valves and a DOHC (double overhead camshaft) design rated at 170 hp at 3400 rpm, and 260 lbf·ft at 1800-3400 rpm (that's a VERY nice range!). A 32-bit ECU controls fuel quantity, valve-timing, and boost pressure at different engine parameters resulting reallygood fuel economy and also full utilization of power during acceleration. Pilot injection is also utilized by the common rail fuel system to smooth engine operation; this means that small amounts of fuel are introduced into the combustion chamber prior to the main injection event, reducing lag time and promoting more continuous and complete combustion. Exterior and interior engine noise is also reduced as a result of this feature. I used to have a Toyota Fortuner with this engine, and it was GREAT! You can see more details here.
 
alright well its only 5lb/ft of torque less than the stock 4bt which is 265lbs of torque but like

BaconYJ said I could easily bumb the cummins up to 450+ torque what can I get with the Toyota? iv never herd of doing a Toyota swap its always been the cummins but I also herd about a duramax.
 
There are still some significant differences... but lets start with Torque. First off, the Toyota Sport model (bigger turbo) has a max torque rating of 412 Nm (that's 304 ft/lb), so you CAN swoop up the engine to produce more torque (there is even a twin turbo version making 645 Nm called the 1KD-FTE).

And speaking of torque, it is important to note WHEN you have the torque available. If you look online, the Cummings torque curve looks like an inverted U, which means that while max torque rating seems higher than the standard Toy's, you only have that max torque available for a brief period, whereas in the Toy, you have that same torque for a wider range of rpm (from 1,800 to 3,600 in the fortuner, but depending on the setup, you can lower this range to 1,400 to 3,200, as it is in the HiLux).

The other thing you have to look at is weight. The 4BT is a heavy engine (well, ALL diesels are heavy because of the thick walls in the block required for the high compression ratios) even for a Diesel. I do not have the specs at hand for the Toyota, but it is a lighter (more modern) engine. Also, because the engine is more modern, you have better fuel economy, not that this will matter much to a trail rig...

I would also guess (I do not have the dimensions of the Toy engine) that the toy engine is smaller. You WOULD need to find a place for the intercooler, though; in the Toy's, they have a scoop on the hood for this purpose, but I guess you can probably fit it between the grill and the radiator.

Being in the states, though, I cannot recommend this engine; you will have a very hard time getting parts. Anywhere else in the world, it would be a completely different story, though. There is a reason Cummings engines are much less popular outside the US compared to German or Japanese engines...

Felipe
 

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How much would that Toyota engine be used? I found only a new one on eBay for $9,000 I can get a good used Cummins for about $2,000-$3,000. I actually like the idea of the Toyota engine better then the Cummins but here the Cummins is probably easier to get.
 
I woul dhave to find out, and it would depend in the country. Here, you would normally look for a totaled HiLux, Fortuner or Prado, and buy it. Should be about $3K, assuming there were some to be had. But again, I would not recommend getting this engine for the states (you ARE in the US, right?) because of lack of parts.
 
Correct I'm in the US in Ohio. But you had me liking the Toyota engine lol. So you would just recomend me sticking with the 4bt?
 

As jfrabat is saying there are better choices out there for a diesel swap, but also as he has stated that here in the States the choices/options are limited without being very lucky finding one.

With that said, what are you plans for the Jeep? Trail rig, DD, little of both? Why a diesel instead of a a gas engine or stroking your 4.2L, etc. Remember none of these swaps and what not are an easy project.

Bacon
 
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