M1008 5.3L Swap

[LateOnTheBrakes]

I picked up a bit of a Frankenstein truck earlier this year. The cab and frame are an M1008 and the bed has been painted (poorly) to match the cab. Two of the rear frame crossmembers are dented pretty badly. Between that and the different bed I assume this thing was rear ended pretty badly in the past.

The truck is a parts bin special of a late 70's set of axles (D44, 12-bolt), a sad 350 SBC, an NP208 transfer case, and an SM465 manual transmission.

The first step was to figure out what I have and document it.

 

[LateOnTheBrakes]

I was almost convinced it was a CUCV clone until I got the dash apart and found the reinforcement underneath.

 

[LateOnTheBrakes]

Got the truck to my family's farm and tried to straighten out the bull bar.

 

[LateOnTheBrakes]

I knew I wanted something a little more modern than the 6.2L diesel or an older SBC. LS engine swaps are very popular and very cheap so I picked up a worn out 5.3L LM7 engine. I figured out it was pulled because of a failed lifter that trashed two of the cam lobes.

I tore it down the a bare block, popped in new cam bears, polished the crank, new journal bearings, new rod bearings, new rings and tried to reassemble with as many of the original parts as feasible.

 

[LateOnTheBrakes]

 

[LateOnTheBrakes]

I wanted to keep the manual transmission so I found out how to connect the old SM465 to the 5.3L.

 

[LateOnTheBrakes]

Finished up the short block this spring.

 

[LateOnTheBrakes]

Got the engine painted Chevy orange and ready for installation.

 

[LateOnTheBrakes]

I used the dirty dingo engine mounts but found I still had to notch the front crossmember to get the truck oil pan to fit. If this wasn't a budget build I would have got a different crossmember from Offroad Design or got a low profile oil pan.

 

[LateOnTheBrakes]

Companies like Advanced Adapters sell kits to marry the engine and trans. But the folks on some forums claim you could use a 6.0L, early 2000s flywheel and the rear of the hardware would bolt together. I reused the SBC bellhousing, clutch, pressure plate, etc. because I wanted to see if it worked before I invested in nicer stuff.

 

[LateOnTheBrakes]

I found the LS3 manifolds I had wanted to occupy the same space as the external, hydraulic slave cylinder. I decided to pick up some Schoenfeld headers because they were rumored to work. I am pretty happy with the amount of room they freed up. They took some massaging to clear the frame for cylinder #3 though.

 

[LateOnTheBrakes]

I found the stock Vortec intake tubing to interfere with the stock fan shroud. I will likely go with a dual electric fan setup. I also found the wiring in the truck to be atrocious so that came out. I got a Painless kit that I am procrastinating on installing.

 

[LateOnTheBrakes]

I cleaned up the slip yoke as best as I could and reinstalled the driveshafts. I am going through now to check/fix the breaks and repack the wheel bearings. I look forward to ditching this junk rear axle.

 

[LateOnTheBrakes]

The worst part of this build thus far has been the electrical work. I'm a mechanical engineer, electricity and wiring are black magic as far as I'm concerned. I sent the PCM to the guy at LT1swap.com and let him remove the vehicle antitheft system. I got the harness from a flex fuel suburban and took the bigger injectors as well. I used his info on the pinouts and wires to remove all the circuits I did not need. It is not pretty but it was enough to fire up the truck and make sure it didn't grenade itself. I will likely buy a standalone harness in the future but this one works for now.

 

[LateOnTheBrakes]

I fired the truck up for the first time in June. It moved under its power for the first time in July. I'm currently working on the cooling fans and power steering. When that is done I will begrudgingly work on the vehicle wiring harness.

There are a handful of things I would like to put as close to the stock M1008 as possible. I am on the lookout for springs, axles, wheels, gauges, etc. The truck is growing on me and I've found the whole process very rewarding so far.

 

[patracy]

Neat. I love my 1008 as a workhorse. But honestly I wouldn't mind having another 1008 or 1009 with a 5.3 in it as a daily. Or even just a older pickup.

 

[LateOnTheBrakes]

I think I would have to figure out how to put AC in it if I was going to make a daily out of it.

 

[joshuak]

Nice work! Definitely giving that truck a second life.

 

[Cucvnut]

It took me about 3 hours to figure out what wires off the stock GM harness will talk to my Ls harness and I depinned the rest of the harness and I will have a keyed ignition.

 

[LateOnTheBrakes]

In reality I think I could get away with two wires. One hot wire to the distribution block to power the PCM, fuel pump, etc. and the starter wire. However, I was so disgusted by the state of the wiring harness I found in the truck that I completely ripped it out. Unterminated/cut wires, wire nuts, etc. I recently spilled a ton of brake fluid on the harness I built. I am very near pulling the trigger on a carbureted setup and ditching the fuel injection.