My Build Thread (year+) on 71 Jimmy 4x4

[RckyMntnKng]

A few pics of updated build items, based on our wheeling trips and dialing in for what seems to work best for the way im using the rig. she is seeing alot of back country, far from Civ trips with ALOT of water and Mud added into the rocks


Added an Auxilary 15 gal fuel tank, with Ball Valve that allows gravity drain to the main tank via a welded in nipple on the stock lower metal tank elbow. No more spare cans everywhere

Ended up using a hitch carrier from an ATV and added vertical legs that bolt to the previous seat mount holes. The seats got moved forward about 4" overall to make room to lay the 39" bogger in the bed. The bogger lays flat and pins to the back of the Tank Rack. Kept the tire hub from the previous swing away mount, and incorporated a pair of grab bars to slide the tire out when needed. All that bouncing around kept bending and torque'ing my other swing carrier

Added a small vertical rack to the edge of the tailgate so when the gate is down it keeps the bottomless cooler from jumping off and floating away in the river - and gives alot of bungee oportunities.

To make more room - removed the wood Subwoofer box and built a compartment in the Side tool box to house the 12" Sub. Squared it off inside with 16 guage sheet and welded in watertight. Fiber sound material added as well as sizing for the air space... finished off with Metal grill guards to protect the sub.

Has been working great so far. Everything enclosed in the cab, with zero hanging from the body. Can use tailgate up or down for cargo room....

[RckyMntnKng]

The open air filter on top of the carb was clogging with mud, water, and turning to mush....stalling my rig in the water crossings and after. Not a good setup for mud and H20 - but works great every where else.

I did some mods to allow a dual setup with a dry intake for just such occasions.

Its basically a mute point in this rig to have a heater - but I can always go back that way in the future if needed. Removed the box/cable components from in the Cab and under the hood. Used some flat plate to built port covers over the passages into the cab from where the Rad/fan would sit in the engine compartment.

Used a cheap Air Raid plastic box leftover from a Cold Air Intake I had on a previous truck and ran tube inside the cab to an Edelbrock Filter with a washable foam element. It got mounted behind the glove box inside the cab where the old Heater controls used to sit.

Every joint and bolt hole got RTV gasket goop and is water tight. Also can cap the firewall port and use the open element carb top filter at anytime im planning to go dry trails.... Works VERY WELL!

[RckyMntnKng]

More Pics of completed intake setup...

Last picture is the flush mounted Boat gas cap - Still need to pretty it up. The stock cap setup that hangs out from the body does not work well in the forrest when you need to squeeze through tight spots

[OldCreek]

Is that safe? Concerns being backfires, gas smell, melted wires...

How about a snorkel?

[RckyMntnKng]

Is what safe?

The transfer tank is no different than any other found in trucks today...or the ones behind the back seat in the cab stock on the pickups of this era. The aux tank is vented, as well as the boat side cap, about 8" apart literally inside the body panels and also to the charcoal filter. Without Doors or a top i doubt any fumes build up. There are no wires to melt in the area - just a gravity tube safer in the cab than anywhere under the body lol. The truck burns 15 gallons in a couple hours of running anyway so that tank is usually empty lmao

If you meant the intake, it sucks air from the cab, rather than discharging fumes, heat etc....nothing to get melted from cooler than underhood temp air coming in. I rerouted all the wires from the picture to alleviate restrictions to the air movement. The stock Foot/flap vents bring in more stinky under hood air than the intake thats for sure. I thought of a snorkel first, but anything that hangs on the body on the outside would get removed unwillingly by a tree or rock on the first trip. Getting it higher may or may not be usefull - any water at that elevation would be above the distributor, in my lap, and ripping the radiator fan apart. Its pretty nice to see if the water level is safe for your intake from the driver seat as well. 99% of the benefit will come from not getting repeatedly spashed and sprayed when punching through mud holes or the river.

I left it dual use and will use stock underhood cleaner on everything except crossing days.

[jc06vmax]

bump for a hell of a read and an awesome Jimmy! I'm just beginning my build and I'm basing a lot of what I'm doing off of your build.

Anything new here since the last post?

[RckyMntnKng]

Jc right on !

Its a great feeling to think someone would base something for their own rig off my old heap -Right on, its def cyclical - I sure as hell based mine off several board rigs and when something works well then reinventing the wheel is crazy right.

I will def be following your build thread and throwing my 2 cents in as you go!

My first piece of advice is, enjoy the work while you work and enjoy the play when you play - and its a win/win all the way around. I couldnt even begin to tell you all the crap I learned along the way.

My second piece of advice is, when you get frustrated at something that isnt falling into place the way you want; stop, take a breather, and mostly drink a beer for inspiration.


I have a few updates in the works for mine - mostly in the Air intake / snorkel department. Incoming soon. Been held up a bit working on a 69 pickup for the last couple months while the Jimmy in the other bay keeps me company.

[RckyMntnKng]

On going work to dial the Jimmy in the way I want it -

One 3" Air tube was too small and lost too much "go" at altitude, and even introduced some rough throttle at times after wot.

Decided to go dual 4" pipes - plenty of air.

I want the filter(s) back under the hood again because the first attempt allowed in some gas fumes / smell - going to twin inline cone boxes under the hood i can seal up.

To get the air inlets up higher i went even more drastic. I decided to narrow the glove box a few inches and modify the dash with some extra real estate for a couple of intakes on the inside of the cab. its very easy to throw on an elbow and go up higher from there anytime its needed.

I took the Glovebox face off, cut the curved portion of the dash opening out on the right side, and re-welded it back into position 4" towards the driver side from stock. Then I took a thick piece of flat stock with two 4" holes and welded it in place to the passenger side to cover the remaining hole.

I then cut 4" out of the center of the glove box lid itself and reinstalled. Used two dash vents from a garden drain that fit nicely for the intake ports

Took it out last weekend this way and it worked very nicely.

Also - I finally pulled the trigger on my range / fuel issue. Im running a 41 gallon tank under the bed now with a new skid and the in-bed tank is no longer needed so opened up a ton of room there.

[RckyMntnKng]

New Tank, Sender, Skid plate - Pics incoming

[MrGraySay]

Originally Posted by RckyMntnKng

[B]As it sits on day 1, see pics:[/

Rear Tahoe seats all shoulder integrated
Rear Seats on "Riser" box to get seat off floor and recess tahoe mounts
Riser Box will double as Speaker/amp holder and tools

I'd love to see some photos of this set-up, especially the "riser box".
What an innovative idea!
Posted via Mobile Device

[RckyMntnKng]

More build stuff. Hopefully furthering the Jimmy's carb'd air/fuel trail for weathering the elements at elevation.....

A day of wheeling in Idaho for me has large ranges in elevation change (2500' - to 8500'). The roads can be anywhere from soupy flower dust, to boulder laden, to deep water crossings. Daily driving/ jetting is at the lower elevation so it does run rich up high and will want as much air as possible. I know I know - EFI is the answer. Well not for me - I like it old school as much as possible mechanical.

This season the Eddy got a dipped cleanup and rebuild with off road needles to help cut down additional flooding on inclines. Also added a large Phenolic spacer to better deal with heat soak to the carb and helps the efficiency of the burn.

The twin enclosed K&N oiled filters I used last season are going to have to take a hike after seeing all the oily dust they let clog things up. Say what you like - but good quality paper type elements have always left me cleaner carbs, and on diesel pickups -cleaner turbos. They (prob due to smaller size) also seemed to be starving the motor for CFM, even down low.

Went to a good self regulated fuel pump for the 1405 carb as well. The 600 cfm carb has a rec'd range of 5-6 psi of fuel pressure. Well the stock chevy mech. pump is/was quite a bit higher than that. This should help cut down on some more of the overly rich conditions.

Air wise - Go big or go home they always say. I picked up a Cummins Opti-Air 1100 series that has the real CFM rating this carb/engine seems to want. A few Pros right of the bat is the internal dust scavenger and valve, nearly water tight case, big 5" inlet/outlet, and spot to add a filter restriction gauge.

Ive fought having a snorkel setup even though in theory I could use it. I don't like the intake pipe mounting along the body - I'd rip that off squeezing through something on the first day. I don't trust the typical forward facing snorkel head to stop water from making its way to the motor. I cant always mosey through a crossing and get to the other side - its gonna splash a wake up on the windshield a lot of time.

Ok - the hat style cap that you often see on Humvee's seems to be what I really should use. Water has less of a chance to splash into the intake - it would have to change directions 3 times in mid air before it could fall down the pipe. Depth wise i'm not going to drive much deeper than the cowl and come out the other side anyways - without a ton more water-proofing of other components. Its getting cooler air than it would under the hood, and its not in the cab itself - possibly letting too many fumes fly around. Its not going to block my forward progress in a tight squeeze, if anything a heavy steel pipe could save me a windshield repair on a tree branch impact lol. There is a small amount of vision restriction to that side of truck, but also on the same token you can visually see the limit of trying to go any deeper in a pinch.

Mods needed for intake exiting the cowl....but in the long run probably my best option. Here goes nothin'.

[RckyMntnKng]

Mock-up, prep and paint etc

[RckyMntnKng]

Field fitting - going to take it out on test run with this setup.

I welded and reinforced two 5" ID steel exhaust sleeve into the cowl so I could bolt in / swap intake pipe length sizes whenever I need or want to.

Right now the carb hat I have is cast aluminum with 4" inlet, So I used a 5" to 4" reducer on the 90deg elbow from the airbox until I find a 5" carb hat.

Used 5" steel flex tubing for a short stretch to go into the cab and align, another 90 elbow and then up through the 3 cowl layers with solid pipe.

[JHT67]

Looks like you've been enjoying it. We bought a Polaris RZR last Fall and finally got it out in the woods the Sunday of Memorial weekend, a place called Powerline Park here in Ohio, it was a blast. I can't wait to do it again, maybe I should bring it out west

[RckyMntnKng]

Tire Carrier upgrades!

So the plan was to build a stout tire carrier that would be removable if necessary....replacing but allowing for the stock tailgate to be put back on at will. (This one utilizes the stock tailgate mounting locations).

Removed the tailgate, unbolted and saved the lower tailgate roll mounts, and the upper tailgate latch mounts.

Used a chunk of heavy wall 2x4 as a bottom plate, cut to width of stock tailgate and added endplates that mount/bolt to the stock tailgate lower roll mount locations.

Drilled out for a 2", 2000lb heavy duty greasable spindle to handle the main loading. Incorpororated a Heavy duty latch that even the Gal can use easily...

Added in a second spindle up higher for the swing portion to make sure the bouncing and jarring wouldn't create sag.

The upper spindle ties into the base plate, the upper tailgate latch mounts, and the roll bar.

[RckyMntnKng]

Used a chunk of female hitch carrier tube, and cut it into the vertical support of the swing door. Set up tire carrier plate and male tube to attach interior or exterior of the rig.

As heavy as these tires are - decided I needed a basket to hold the tire up for loading/unloading essentially. You basically sit the tire in the basket and slide out the carrier plate and bolt it to the rim. Ended up working perfect - and with the addition of some turnbuckles and metal cable supports, the tire basket and hitch slide portion gets zero rattle after 2 trips into the Mtns with her.

The base plate is also supported by the rear bumper and frame rails. 2 kickers run between the bumper and body, attaching to 4 tabs and clevis pins. The top supports on the swing away have slip tube mounts for during removal of entire setup.