LS swap 1999 c3500 single cab lb

I’ve always wanted a single cab gmt400 hd truck, found this one whitch is a c3500 single cab srw that used to be a service body truck. Has 300k miles but absolutely not a spot of rust! And suspension is in good shape.



Picked this truck up cheap as dirt and immediately had a plan for it:

All aluminum 4th gen (lh6) 5.3 motor 9.8 to 1 compression with flat tops and 799 heads. Paid 490 out the door at local scrap yard.

The stock 80e (whitch I have gone through and installed transgo hd2 kit in) and full float 14 bolt will hold plenty of power.

Other than that and some cosmetics my plan is a badass daily.

GOALS: I will add these to the thread when I get to them.

RETAIN FACTORY AC—
I know this one will be tough, but I believe it can be done, I will use a billet ict alternator relocation bracket and custom fab a 4 bolt bracket for the ac compressor IN THE FACTORY LOCATION. I hope to be able to do this without ever opening the ac system hence making a good option for all us low budget guys wanting an ls swap. And living in the south, ac is a must.

TURBO—
I have already sourced out all the parts and stuff needed to do a turbo on this truck
When tax money rolls around next year I will be purchasing all exhaust components and parts for the engine, decided an on3 76mm. Will be the best bang for the buck and give me good power for what I want from the truck.

Btr stage 2 turbo cam, on3 76mm single setup, forged internals or stroker forged internals, arp studs for everything, custom manifolds.

Past month got the engine and trans gone through and mounted together, used the dirty dingo ls swap motor mounts to mount in the truck, honestly best purchase so far, made the physical swap totally painless. Trans is sitting in the factory location no problem.





Engine and trans in and mounted now begins the long list of hard stuff. I am attempting to keep the factory harness intact for the ac controls, factory gauges, speedo, abs, etc. SO FAR this has been a total headache, my advise to anyone trying to do this DO NOT CUT ANYTHING, I don’t care if it’s ugly zip tie it up tape it do what you gotta do but don’t cut anything. I am now stuck with the headache of trying to get the nss to work and this thing isn’t grounded and these wires are crossed etc. all because I wanted to cut the factory engine stuff off to clean it up, just don’t haha. I have working gauge cluster at the moment but negative on nss and backlighting.

For the drivetrain I purchased a PSI ls swap harness that is a very nice piece in my opinion for the price, I have a 4011 pcm tuned by a local speed shop in hand already. Currently in the process of getting this harness ran and everything plugged in and wired properly....much patience required. If I keep working at it I might have this thing ls swapped and running in less than 2 months.
The intake on this 4th gen motor is for a 4 bolt dbw throttle body so I bought a FITech 92 mm throttle body (very quality part for only 150 bucks) and modified a early truck intake throttle cable holder to run a drive by cable setup on a larger mouth 4th gen intake.

Fuel system
Was pretty simple, ls rail is return less and this truck comes with a return fuel system, run an ls1 corvette style fuel filter that is internally regulated (58 psi) it has a return nipple on the input side, run hoses from your pressure to the filter, filter return to truck return, and from filter output to fuel rail.

Putting together little stuff and systems like power steering and rad right now, should be running and driving in the next week or so.

My buddy’s ls swap c10 is pretty badass too
He’s been helping me allot with part choice and doing the swap.

Engine bay starting to look better, picked up some nbs 2500 ltz wheels for 400 bucks, practically stole them, gonna change the whole look while maintaining stockish setup.

Made HUGE progress on the truck this weekend. The whole engine bay is now mocked together, power steering and hydroboost are functional, trans cooler lines are cleaned up and not leaking, and the whole cooling system is together. I am going to have to heavily modify the factory fan shroud (i will be running electric fans but i want the shroud for aesthetics) to run the ls rad hose and i have a very roadkill style air cleaner on in order to clear the mechanical fan. but all systems are operational. The truck does run and will go down the road, but there are some issues:

The transmission is in limp mode for an unknown reason and the ecu is freaking out with erratic cam timing signals (throwing 3 cam position sensor codes. My hunch for the issue is the tune, i do not think i gave my tuner enough info when i dropped the computer off to him. What i think is loaded to the ecu is what i assume a 58x reluctor tune for a rear cpm l33 with a pin swap (and add) for the 80e. Since I'm running a psi harness made for an 80e it would not be a tune pin swap but an actual 80e tune for like a 6.0/80e combo just with a 5.3. ALSO my engine is a gen 4 2005 LH6 5.3 which is a frankenstein of a motor. it is a 24x reluctor with a Front cpm and a 3 bolt cam. I will be setting up a tune date with powerhouse performance and hopefully we will resolve these issues. Symptoms now are hard start, backfiring, erratic idle, no power, erratic timing adjustment, and limp mode trans.

Updates whenever i resolve the issue.

Worked all night after work past couple days to get full exhaust on the truck and work out some wiring issues. Finished just in the knick of time to drop it off at my tuner so she’ll be ready next week.

Had to install gen 3 knock sensors on the outside of the block and make a custom wiring harness for them. Also had to swap the outside two wires in the cam sensor to make the gen 4 sensor work with the gen 3 computer. Only codes in the pcm are tuning related now. Ready for the first burnout in this thing!!

Big setback today....while my tuner was street tuning the truck today one of the factory DOD lifters collapsed. Very pissed but i knew what i was getting into with this gen 4 motor....should have swapped lifters while the motor was out.

Looks like ill be upgrading the valve train and doing the cam swap sooner than later. Heres the plan:

ls7 lifters $100
BTR stage 2 turbo cam (226/231 .605"/.598" 113+4) $390
BRT .660 springs, titanium locks and retainers, 5/16 pushrods, black seals. $320
BTR factory rocker trunion upgrade $120
CXRacing (eBay) headstuds $110 did my research and everyone is saying these are as strong as arp headbolts and can be reused.
ls9 head gaskets $120
3rd gen lifter trays

Total $1160

OUCH, allot more than i was wanting to spend at this point of the build, but its necessary. Gonna be a while before i can scratch up the cash but the build will continue. Me and a buddy of mine have been flipping junkyard parts for cash and might be able to come up with the money in a few weeks.

Truck is noisy on startup but smooths our when lifters pump up, I think the tap is just a sticky dod lifter and not collapsed. Truck still running crappy but she has a little power and the trans is BADASS squats and chirps the tires into second gear. All gears work and lockup.

Tested her out cleaning up all these downed trees from Florence.

Well, seems as soon as I get a truck back together I tear it apart.

Drivetrain is out, sold trans to buy 3200 circle d stall and installing the built trans out of the big truck. Bought a BTR Stage 4 truck cam off a buddy of mine, installing that, new springs, dod delete, and freshening up the block and everything else.

Plan is while the drivetrain is out to clean and paint the entire frame, install a 2-3 drop with poly bushings, fab up some rear trac bars, and install a rear sway bar.

Engine is apart. Bad news is it needs new pistons, skirts are in bad shape on the old ones. Doing a full rebuild at this point because all the bearings were in bad shape too. Machine shop said the bores looked ok so going with stock bore but he is going to give the block a good once over. All the other parts got cleaned in my homemade “hot tank”.

This worked very well:
Metal trashcan and lid $15
4 gallons of simple green $40
Fill with water
And any way you can think of to heat it up, I used electric hot plate.
Heat first day, let soak a few more, then pressure wash.