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Build-RBV 4800 U4 bronco II


Aug 27, 2020
Member Number
Kent Washington
The inspiration on this build was the 4500 race class. I wanted to build something that would be used for recreational wheelin and doing some racing. I had big dreams with little to no funds when I started so it took many years to finish.

Started out as 84 Bronco II. I will start this with a before and current picture and then continue to post build pics from start to finish.

Ranger truggy
4.0 ohv
M5od with 2wd 4cylinder gears
1350/1354 doubler
Dana 44 rcvs spool
9” rear
3 link front with hydro assist
4 link rear
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Once I got the rig torn apart I cut the back off to tube it out. I started in the rear and did the rear suspension in plans of putting a Bronco II cab on so I established wheel base off that. Everything is 1.75 .120 wall. Dom.

Once I got the rear done and was happy I flipped it around in plans of just keeping it simple with the stock frame but I got excited with the grinder! I did not have a engine stand or a cherry picker at the time so I built the jig to Hold the drivetrain while I built around it. At this time I was wanting to build it with the gear driven 2.8 to keep things simple





Did the front tube work and got the front axle located using the donor ranger as reference for dimensions. Set the wheel base at 109”.



at this point I got the cab on, dropped it 2” on the chassis to get a lower cog. Steering mocked up and track bar mocked up. The front bash tube is 1.5 .120 tube so we will see how well it holds up. Little more frame work to give it more character as well.





Anyone know why the pictures are so blurry? I am posting from an iPhone. They clear up when you click on them.

I new I wanted to run a 2 speed rad fan and found the volvo fan. Seemed like a good deal. You can get them at the local parts house. So I made a aluminum shroud that fits the fan great and super snug to the rad.




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I yarded out the 2.8 and dropped the 4.0ohv v6 in. Built a intake manifold that worked with the body drop. Stock intake manifold damn near stuck out the hood and I wanted the throttle body in the back.

built the turbo headers out of 304l to fit a t3/t4 turbo. Waste gated at 8psi and a exhaust ar.48

Ran with the bigger mixer from got propane so I would not be limited by fuel delivery.


Beautiful build :smokin:

Which steering box is that? Looks like a 4x4x2 setup. Are you running hydro assist?

How's the Dana 44 holding up to the 39.5s?

Any internal work on that 4.0L, or head studs at least?
I should be adding some info and tech to these Posts!

it is a A non modified 4x4 70s f150 bronco box with a custom double shear arm. The 4x4x2 mod is the exact reason why I choose this box from the beginning. I was not sure how I was going to Orientate the box so being able to flip the box seem like a good option!

so far on the three trips I have had on it everything has been holding up. My concern is ring and pinnion. I have it currently setup with very little steering angle in hopes of that keeping it alive when beating on it.

the guy I use up in Canada for 4.0 parts talked me out Of studs and just went with a stronger bolt for a higher torque spec. So far so good. Still wish I went with studs so I can reuse them on a engine I want to build down the road when I get all the bugs worked out. Seems the magic number for longevity is 7-8 psi of boost. I ran with a 8psi waste gate and I am fluttering between 8-10 pounds so we will see how it holds up.

Thanks! I have wheeled the rig about 6 times and raced it once. Had some issues with the propane side of fuel. Ended up destroy an engine and had a propane mixer failure.

got another engine in it and a new mixer and it seems to be good now. Unfortunately it is back torn down to work on getting it prepped to run a local race and a U4 race in Montana.

I will post the rest of the good pictures I got of it before i tore it down. and we will start some more tech from there.
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