1971 Jimmy with 6.0 LQ4 / 4L65, 4" lift/33s.. basic family fun cruiser

[Haggar]

I have been meaning to post this up for a while. This is a small description of my 1971 Jimmy build. At this point (Sept 2018), it's running and driving. But I thought I would post to show the way I did the swap, in case it's helpful for others. If you have questions, please ask


A few years ago, I purchased a 1971 K5 Jimmy, as our family couldn't fit into my Jeep CJs anymore, once we had our 3rd child. It was a decently solid starting point, ran and drove, but definitely had it's issues. It has been in a front fender bender, the front bumper was twisted, and the drivers side front fender is a JY replacement. The original 350 was replaced at some point with an older 283 that was pretty gutless. It still had the original NP465/NP205. The purple paint isn't very good (was originally a Yellow with white interior). It had a single wall hardtop, which I yanked on day 1..

[Haggar]

So, I decided to swap to an LS motor, and to an automatic, as this is for a family cruiser, with a slight chance that we'd take it to the sand dunes. I like the look for a lift and bigger tires, and this gave clearance for the front axle <--> oil pan later.

The lift is a Tuff Country 4" EZ Ride, and I added Bilstein shocks, I believe the 7000 series. Tires are 33x12.5R15 General Grabber AT2s on 15x10 Aluminum wheels.

I think I lifted the back first, then waited on the front because it's easier to do the engine swapping with a lower vehicle height..

Overall, the rust isn't too bad, and things came apart pretty well. I'm in Michigan, and everything is usually rotten here, but I had this shipped in from out of state. The only stubborn part was the cone washers on the steering arm refused to come out. I've done lots of cone washers on Toyota axles in the past, and am pretty good with them, but these were a nightmare. In the end, I had to drill each washer into several pieces, and remove the remaining splinters, then another 30 minutes with a sledge to get the arm off the studs. Fun times.

So I got the back done.. then it sat for about 3 years as life and lots of business travel got in the way..

[Haggar]

I had started the project, with a drivetrain in hand.. an LS2, a built RMVB 700R4, and a full time t-case (BW4472).. this was from a Jeep project, that got scuttled, due to the family size addition. Well, the LS2 became a 403, and I didn't want to swap to a drivers side diff, so I decided to look for a different drivetrain for it. (The Jeep project was going to be more of a hot rod, but I wanted a milder engine and real automatic shifting in the Jimmy)..

So a friend gave me a 5.3 that he had laying around, with some type of valve spring issue. After I inspected it, I found a broken valve spring on #7.. a borescope showed the piston hit the valve, and compressed air showed it was bent and leaking... So, on to engine #3..

Still wanting just a stock engine, I decided to find a 6.0. Found a nice low mileage LQ4 long block from a Hummer H2. I could use the intake and accessories from the 5.3 on it to get a complete engine. When I got this one home and started cleaning... I noticed the ports were CNCd... hmm, interesting. (I got it from a local wrecker, it was already shrink wrapped on a pallet when I got it, couldn't see the small details). More inspection showed ARP bolts, a pinned crank pulley (which explains why this one was sold with no intake manifold..).. The heads were stock CCs, but had aftermarket dual springs and retainers, and there was a Lunati blower cam installed.

At that point, I was not going to end up with a stock engine anyway.. so I scrounged parts left over from the LS2. I installed a Comp 223/231 cam with .637/.617... big lift, but the ported heads should take advantage of the lift. I think its on a 114 LSA, and has -1* of overlap, so would give me some idle chop, but drive well. This is a PCM of NC Attitude V2 cam that I had on the shelf. This cam is designed for a heavy Trailblazer SS, so I figured it was a decent enough match for the Jimmy.

I had some Corvette 33# LS2 injectors on the shelf also. Paired this with Doug Thorley 1-7/8 Tri-Ys, since no one else makes swap headers for a 4x4 early K5 swap.

I tried to keep it low key, so spray bombed it all rattle can chevy orange, and did some black crinkle paint on the valve covers.

The Transmission is the 4L65e from the same Hummer. I installed a Corvette servo, and changed the filter in the pan, but that's about it. A Yank PT3200 converter finishes this section off. I got a Lokar top mount shifter, I Think 17" tall, matte black with a mushroom style head, it looks very close to the original SM465 shifter

[Haggar]

Oops.. I used a Dirty Dingo swap crossmember to mount the engine. It worked out well enough, and had no clearance issues with the stock truck oil pan. There is a lot of adjustability, I have the engine slid forward I think as far as it can go, which lets it just clear the firewall. I think I had to hammer a small corner of the trans tunnel on the passenger side to clear the headers, and needed to trim the top rail of each side of the frame, to clear the headers, also.

The Engine harness came with the 5.3... it was a Painless Wiring Red/Blue swap harness. It turned out to be quite nice, and I had no trouble with it. In addition, I installed another fuse block/power distribution block, and additional relays to control things like the fans. The ECU, engine fuses, and relays, are mounted on a bracket that I made, which is inside where the glove box was originally.

For the fuel system, I had an aeromotive phantom setup (with the yellow foam and black rubber sump) on the shelf (I had a lot of things on the shelf!!, This build let me reuse a lot of parts from half-done builds)... I didn't need or want the Aeromotive 340 pump for this engine, so I replaced it with an Amazon sourced Walbro 255. I installed all of that into the stock gas tank, which was a brand new aftermarket poly unit that the PO installed. After cleaning it, I cut the hole for the pump with the tank completely full of water to attempt not to blow myself up. I had leftover AN fittings/hose to get up a few feet to a Corvette filter/regulator, and then from there, I used a Dorman repair kit to build the Plastic(Nylon?) 3/8 lines up to the fuel rail with the correct quick-connect fittings. I really liked this stuff, and overall, the whole fuel system has worked flawlessly so far.

[Haggar]

For the transfer case, I used an NP208 from an 80's K blazer. I used an advanced adapters 6 bolt 4L60e to 4 bolt output adapter, which included a 40 tooth tone wheel and VSS. This works with the factory output shaft, just bolts on, this all bolted to the NP208.

The transfer case mounts were the same as the NP208, so it all bolted to the factory crossmember, but it was moved forwards few inches.

I still don't have a front driveshaft installed, and I never installed the 4WD shifter.. just laziness on the shifter. I have the factory one with all the hardware from the same 80s blazer.. but I want to make it look more correct for 1971, it's a little plasticky.

Amazingly, the stock 80s rear driveshaft fit almost perfect, with just a conversion U-joint at the rear to mate with the 12 bolt.

My first test drive showed bad vibrations on deceleration.. this opened a whole can of worms. Turns out, a previous owner tossed in gears without any shims in the axle, and the pinion nut wasn't torqued.. it came loose on the test drive, and the pinion gear was eating into the carrier. Luckily I limped it home without issue.

Under the philosophy that anytime I take something apart, that's the best time to upgrade.. I swapped the Open 3.73s for 4.56 gears and an Auburn LSD. I struggled with the crush sleeve.. Wouldn't crush, then after pre-crushing in a press, it crushed too much.. trying to get the 2nd one right actually stripped the threads off the pinion nut! I ended up with a solid spacer and shims, and it dialed in perfectly. I used a Ratech pinion depth tool from Summit Racing, which helped out on the install. So everything was nice and nice, including all the wheel bearings, seals, correct preload and backlash.. Install it back into the truck, and then I can see that it's really close to binding, due to the shaft angle.

So, it was time for a CV shaft, which I got from Tom Woods, who I've had good luck with before. When I went to cut and rotate the spring pads, I found they were scab welded on and the welds were rusting through and cracked. So I'm glad that I found this. Looks like it came from a different vehicle and then someone welded the pads to fit the blazer, but I can't figure out why. Anyway, in the end, it all came together, and is working great now. The 4.56s make the 3200 stall converter happy, and the LSD is good and tight.

[Haggar]

Lets see.. what else..

Brakes, I got a Booster and Master, I Think from a same year C30 truck, bigger bore and larger booster. A little filing of the holes on the bracket let it fit, and I didn't need to mess with the pushrod length at all. I had to make new lines to the combination valve, since the ports are swapped on the new master cyl.

I used stock replacement disc and calipers up front, with some longer rubber hoses (also maybe from a 1 ton truck.. but I would have to go back and check). I replaced most of the hard lines on the truck with new ones that I bent and flared. I used the NiCopp lines, and they flared easily enough.

Exhaust I have full 2.5 exhaust that I cut and welded from a pile of mandrel bends and straight pieces. I added an H pipe/crossover just after the T-case, and use some 20" long Borla straight through mufflers. It sounds pretty nice, not loud at cruise, but barks well when I get on it.

Steering was pretty sloppy in the box, so I replaced it with a reman unit from Redhead Steering Gears.. the 15:1 box. Works excellent, and improved the wandering a decent amount. It was at zero toe, so I put a small crank of toe in into it before we did Woodward Cruise this year (the first real long cruise for the truck). It needs a little more toe in, but it drives fine at 65mph. I installed a steering stabilizer when I did the lift. I am using the original 1971 power steering lines, with an adapter to go from O-ring to Metric Flare for the pressure line. I just capped off the 2nd return line on the LS pump, I tihkn that is for hydroboost return in those systems?

[Haggar]

Cooling system.. I tried to use the factory radiator, but it ended up having several small leaks. So I am using a modern replacement for the 4-core radiators.. this is a 2 core Aluminum with the plastic end tanks. But it's been fine with no leaks, and the truck runs rock solid at 190 degrees. I have a trans cooler in front of the radiator, and am using a Ford Windstar dual electric fan, which has a built in shroud that fits very well to the stock size radiator. I am using a 3 relay configuration, with low and high controlled by the stock ECM. I did have to add a wire to the ECM connector on the painless harness, but I was able to steal a pin from some unused emissions wiring for this purpose. The 3 relay config runs both fans in both low and high, but switches them from being in Series to being in Parallel. I am using some generic 40 amp relays from Amazon, no problems, and I keep spares, just in case.

I had a reducer for the upper hose laying around for year, its a Jags-that-run part, that converts from the smaller size LS upper hose to the larger old style hose. I just used a silverado 5.3 upper hose, and a stock Jimmy hose, cut them about at the middle of the radiator, and joined them with the JTR fitting. The steam line runs into a small pipe nipple in this fitting also. I removed the heater box, and just used one of the small formed U-bend hoses to bypass the heater. I forget the application for the lower hose, but its a Gates part, that I found the part number in one of the other builds on this site. It just needs to be shortened a little.

With this setup, we hit woodward cruise this year. I was nervous, as I always had cooling problems in my older Jeeps. The day was upper 80s, I'm sure over 100 degrees at street level in the sunlight. With 3 hours of mostly creeping at idle, the engine never got over 194, and the trans never got above the 160s, so I am very happy with the cooling system.

[Haggar]

For the intake, I got one of the 4" plastic builders kits with the different bends, and a few silicone 4" couplers. I got a universal K&N cone style, which had a small stud at the end. I routed the filter over behind the drives side headlight, with a bracket that I made to hold this stud to keep the intake secure. The MAF is in this run, near the filter. I cut some plastic, and made a box around the filter, to be a cold air intake, as I was seeing IATs over 120F. I cut an opening in the front of the inner fender to let in outside air.

For gauges, I had a set of VDO cockpit whites in an old Jeep dash that I built (I *really* had too much laying around the barn..). I installed the corresponding fuel sender in the tank when I did the pump. For the oil pressure sender, I took the OEM GM sender at the back of the block by the intake manifold, and gutted it, drilled and tapped it to accept the VDO sender. The GM one is only to supply the stock truck dash, not used by the ECM for anything. The water temp is always tricky to get into the passenger head without drilling and retapping it. However, there is a block heater block near the starter that goes to the water jacket, so I have an adapter fitting here with my water temp sender. I also installed a trans temp gauge, which the sender screwed in without any adapter into the pressure test port near the shift selector on the 4L65e. Both the water temp and trans temp match well to the data that I read out of the ECM with my HP Tuners scanner. The tach is driven by the ECM, with the tach itself being configured as a 4 cyl, and a 1k pullup resistor on the tach signal line. The VDO Speedometer is hooked directly to the ECM sppedo output, and I can fine tune it with the PPM output and tire size in HP Tuners.

The gauges are just temporary for now, I Will make a nicer gauge cluster that looks 1971 but uses the modern guts. For now, I gutted a spare gauge cluster and the small gauges fill the bottom 4 slots. I also have an NTK wideband, which is mounted in the center of the cluster in a bezel that I 3d printed. There are also indicators there for the high beams and check engine.

[Haggar]

As stated, I've been doing my engine tuning with HP Tuners.. this is my first time doing this, so I'm slowly learning. It's running decently, with about 400 miles on it now. I still have more tuning to do, but it already makes pretty good power.

I think that is most of the LS swap related items. I will try to dig up more pictures to go with all the words...

[Haggar]

Other than that swap stuff, I've added a Softopper, which went together without too much issue, and I did a stereo last weekend. We didn't have any interior panels, so I got the basic plastic front kick panels, without speakers. I had to make a spacer for them (I cut rings out of 1/2" MDF) as my speakers were too deep to fit. I used JBL GTO series 6.5" components for the front, and covered the panels with grey felt, as I didn't like the shiny black plastic.

For the rear, I made simple panels of 1/4" plywood (that literally was sitting for 20+ years in my dad's woodshop). I backed the speaker area with 1/2 plywood for stiffness, and cut pieces of 1.25" x 0.120 aluminum angle, which I riveted to the floor and wheelwell to secure the bottom edge of the panels. More grey felt and sound insulation mat went on the wheelwells, since the PO had sprayed with some bedliner that was very rough on the skin.

I build a sub box for the cargo area, and a carpeted board under the back seat to put the amps.. an old Sony Xplod 50W x 4, for the main speakers and an MTX 1000.1, set to run 600 watts to the sub, which is a dual voice coil 12" Sundown SA-12. A retrosound stereo is in the dash to control it. I'm going to try to 'mold' the OEM GM radio face, buttons, and knob over it to make it less... shiny.

[Haggar]

So, as of today, its a nice cruiser. It has plenty of body issues of surface rust, paint problems and panel alignment, etc. But you can get it in it and go, no prob, and no worry about getting dirty or scratched.

[72ironmike]

Awsome !

[jaros44sr]

Welcome to the boards
Nice build, good write up
Never saw those wheels before, I like them
How's the exhaust work with dumping in front of tire

[Haggar]

The exhaust dumps out the back now, the previous owner had it out the sides. The only gripe with my current setup is if I have the soft top up with the side windows up, but the door windows rolled down and the back window out, it sucks in exhaust inside pretty bad. I was hoping with the front door windows rolled down, and vent wing windows opened, that I'd get enough breeze to keep fresh air inside, but no dice.

Part of the issue is that I'm still working the engine tune, so it's a little rich in places. Getting there..