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B3.3T Jeep YJ


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Old 08-15-2006, 08:18 AM   #1
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B3.3T Jeep YJ

Thought some of you might get a kick out of my re-power project. It started with a 1990 YJ Jeep with a 4.2L inline 6 carb motor, AX-15 5spd tranny and 3.07 axles. The tranny and axles are important for adapter availability and rpmís (with the 30 inch tires on the jeep Iím turning 1600 rpms , torque peak, at 59 mph).

Iíve wanted to do this type of project for quite some time. After many months of researching I came to the conclusion I wanted to use the Cummins B3.3T for the engine. This was due to its simplicity (all mechanical), relatively light weight (~560 lbs with starter, intake and exhaust manifolds, etc.), physical dimensions (itís much shorter then the 3.9), local service/parts (the Cummins dealership in Cedar Rapids is first rate), cost ($3780 for everything including intake grid heater cold start option), good torque (215 lb-ft @ 1600). The trick was finding a way to convert the SAE bellhousing into something that would work with an automotive transmission . . . Thereís a company called Phoenix Castings (http://www.phxgrp.com/transmission.htm) which makes just the item!

After talking with the old engineer there I decided to go with the SAE4 to GM small block adapter set, and then used an Advanced Adapters AX-15 to GM full bell housing kit. The pictures in this photo gallery will help visualize what these adapters look like and how they interface:
"Update: The yahoo picture site closed and the pictures are now located at:

I wanted to avoid doing any body lifts so I ended up having to cut some clearance areas into the hood. I then used a hood scoop to cover up the holes. If a person did a 1-2 inch body lift there would be no need to cut the hood.

So far Iím extremely happy with the result. Itís been 1.5 months since I started driving it. Have ~1300 miles on it and its running great. Getting 30-32 mpg on mixed driving. It has no problems going 75 mph on the interstate (although itís loud Ė the aerodynamics are horrible). The acceleration is adequate (although some of the power monsters on here would certainly call it inadequate). There is lots of tweaking that could be done to increase the performance (all the injection pump settings are easily accessible and adding an intercooler could easily be done). This project still has lots of possibilities in the next few years

Hope you all enjoy the pictures.
2011 BMW 335d
2004 Cummins 4x4 Quad Cab SWB
1990 YJ Jeep RePowered with 2006 B3.3T
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Old 08-15-2006, 10:18 AM   #2
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Thats sweet MPG! I might have to think about one for me.
1993 W250 Clubcab 5spd, 3.07 gears, Green/Tan, Isspro Boost, pyro, fuel pressure and tach. 7'6" Meyers Plow. 3 inch Straight pipe. MagHytec Diff cover. Alocas with 265/75's BFG AT's, HX35 12cmWG, P3 Brake controller, 110gal bed tank, BHAF

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Old 08-15-2006, 10:55 AM   #3
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That is cool.
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Old 08-15-2006, 11:02 AM   #4
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Nicely done! Great veichle for a small diesel engine.
1996 Ram 2500 Club Cab 4wd AT 138k
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Old 08-15-2006, 11:50 AM   #5
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That is sweet! I want one!

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Old 08-15-2006, 01:44 PM   #6
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What kind of tranny did you end up using?? Now you got me curious DANG IT!!!

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Old 08-15-2006, 02:07 PM   #7
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Great MPG!

Nice job! What do the motor mounts look like?

It seems to me that this would be a great bronco / blazer type conversion too!

Yeah, an intercooler would be good for some more hp, maybe 20-30?? ANd maybe better MPG, too!

What was your original MPG, with the gasser?

My diesel Fleet:
2006 3500 QC LB Dually, Cummins, Auto, Jake, Laramie (no kitchen sink), Gauges for Fuel Pressue, oil pressure, Boost, Water temp, trans temp, diff temp, and pyro 19MPG Freeway/14.5 City
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Old 08-15-2006, 02:13 PM   #8
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Nice... My wife has been asking me if I could do that to her Cherokee... the 4L love gas and the 3.3 looks like a good cantidate... Did you keep the original Rear gears? is that the original Jeep manual tranny?
Shes been looking at some older CJ's so maybe...

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Old 08-15-2006, 02:32 PM   #9
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Now you got be looking...What made you choose the 3.3? Why not the B3.9? 99HP & 315Tq? Yes, it's ~3" longer....

Just curious.....

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Old 08-15-2006, 03:00 PM   #10
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I chose that particular jeep model because the 1989.5+ yrs the YJ got the AX-15 with the inline 6. The AX-15 is a good candidate for the swap as it's pretty rugged, and there's lots of adapters made to connect it to a GM small block. Also, the inline 6 YJ's came with 3.07 axles as compared to the 4.10 with the 4 cylinder. Needed the 3.07 axles for rpm reasons (I wanted something I could drive at interstate speeds without redlining the engine). So, I kept the original tranny and axles.

Also re-used the radiator and it's way more than I need for cooling. I'm using an electric fan with an adjustable thermostate, and if I set the temp to come on above 190 deg it never kicks on. The B3.3T engine's thermostate starts to open at 180 and is fully open by 200 according to the owners manual.

I'm using two sets of mounts per side (the engine has three mounting possibilities per side). The front ones which are doing most of the supporting are cobbled together from L brackets. Two L brackets welded together with gussets that connect from the front engine mounts to the original jeep frame mounts (had to trim the tips of the jeep frame mounts for clearance) with about an inch of rubber dampening the vibrations. The rear mounts are just a single L bracket connecting to the rear engine mounting location and extending to the frame rail. The end going to the frame rail has a rubber foot for vibration isolation and only supports the engine in the verticle direction.

I was concerned with the weight and size of the 3.9. When I said the 3.3 was shorter than the 3.9 I was mostly concerned with the height difference. Would've taken a lot of body and suspension lift to get the 3.9 in there in such a way to not worry about the front axle hitting the oil pan. Also the 3.3 is about 200 lbs lighter than the 3.9.

The old 4.2 carb motor was giving me about 15-16 mpg in mixed driving. So I've effectively increased the fuel economy by 100%. The tires on the jeep are 30 inch mud tires with very aggressive tread. Could probably gain a few more mpg with A/T tires. However I like the looks of the mud tires

Also, I'm using an electric vacuum pump (Stainless Steele Brakes makes it) to run the brake booster so I still have brake assist. I do not currently have power steering and doubt I'll hook it up. It steers a little rough going slow but it keeps my wife from driving it.
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Old 08-15-2006, 03:11 PM   #11
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Is there no option to add a vacuum/steering pump like on the 5.9 or the 3.9L?
92 Black W250 295K, getrag, valair 13" ceramic clutch, dana 80 3.54, HX40, DDP3 injectors, high pressure piston LP, custom IP, M&H M2 fuel pin, PS charge air cooler, 4 in exhaust w/ brake, gauges(and lots of them) Leece Neville power.

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Old 08-15-2006, 10:12 PM   #12
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would love to see some pics!
'99 Dodge 2500, 4x4, 5spd, SB 13" Con FE, Drag Comp, Jammer 5s, HX35/HT60 TWINS
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Old 08-16-2006, 04:10 AM   #13
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Originally Posted by jhurst
would love to see some pics!
Me too!!

1998 Dodge Ram 2500 QCSB 12v 5-Speed 4x4 3.54 gears - SDX 5x.012, S300G Turbo, Custom Fuel Plate, pull cable shut down, 4" straight pipe, GM 1 ton wheel cylinders, other stuff...

sold...2006 Dodge Ram 3500 4x4 6-Speed QCLB / 1997 Dodge Ram 2500 4x4 Auto CCLB / 1993 Dodge Ram W250 4x4 Auto CCLB / 2002 Dodge Ram 2500 4x4 6-Speed QCLB

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Old 08-16-2006, 07:09 AM   #14
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Regarding the power steering pump: This is an industrial/ag engine, not an automotive engine, so options like power steering pumps and vacuum pumps are very limited (that was part of the reason for finding the Pheonix Castings companies adapters which will convert an industrial SAE bellhousing engine into something an automotive transmission can work with). There is at least one PTO output on the engine that I was originally planning on using to drive a simple sae style hydraulic pump with a pressure relief bypass valve to drive the power steering, but it's really not that bad without the power steering. And not driving the pump also saves some hp and uses less fuel. I'ld rather let my arms work a bit harder at this point than fuss with adding the hydraulic pump.

To the guys asking for pictures: If you click on the link in my first post it should take you to the photo album on yahoo with lots of pictures.
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Old 08-16-2006, 07:13 AM   #15
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One thing I forgot to mention regarding the engine. The B3.3T uses an automotive style rotary injection pump. So even though it's an industrial engine, it uses an automotive style injection pump. The non-turbo 3.3's use an industrial style inline injection pump.
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Old 08-16-2006, 07:13 AM
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