1988 K5 LS 5.3 SWAP Hi all, I’ve been looking through CK5 and other message boards for going on 2 years now planning a Colorado emissions legal LS swap. There’s a ton of great information out there, but not all in one place. So I’d like to put out a part-by-part narrative how mine went. Sorry in advance for the length of the post. My rig was a totally stock 1988 TBI 350 with 200,000 miles. It still ran well and passed emissions, which means the 350 was worth a few bucks. Also since it was already injected it made certain components of the swap easier. If you are starting with a carbureted truck, not much will be different but read to the fuel section. Donor In metro Denver there are plenty of yards offering take out engines. Calling around, that might be the way to go if you just want a long block. But all of the accessories really would have driven up the price. I ended up buying a fleet model 2002 Tahoe with 159,000 miles with a L59 Flex Fuel 5.3, 4WD and a bad transmission for $1,900 plus $125 for a tow. It would drive it around in 1st and 2nd gear. I put a scan tool on it, and had the emissions test info, so the engine seemed solid. The 5.3 got new plugs, wires, water pump, intake gaskets, and PCV valve, along with a power wash, before dropping into the K5. I sold off the unneeded Tahoe parts and scrap for $1,627. I put all 4 wheels and the two brand new tires from the Tahoe on my 03 Suburban which desperately needed them anyways. That saved $350 bucks, so that’s $50 for the running LS and all of the donor parts I could use. Removal I put of the 350TBI and 700R4 on Craigslist while still running in the K5. Someone bought the whole setup for $700. I carefully removed all the TBI wiring and computer for the buyer, keeping leads to the cab for the check engine light, factory tach and TCC brake switch which will be required for the LS swap. I removed the hood and core support, left the fenders and bumper in place, and pulled the entire powertrain including transfer case. Here's a pic of the 350 ready for sale, with the TBI wiring harness removed and labeled for the buyer. Transmission My donor truck was a drive-by-cable throttle setup, so it would have been possible to use a Bowtie Overdrives EZ kit to keep the 700R4 tranny. But you still need to deal with a vehicle speed sensor, which the 700 does not have. Also, the condition and miles on the 700 were unknown but it shifted fine and was worth some money. So it was really a no brainer to go with the factory 4L60E computer controlled setup. There was no way I was going to put a high mile used transmission in my K5, so it didn’t bother me that the donor had a bad trans. I took the dead trans over to a trusted local shop and exchanged for a rebuilt unit with a warranty. This took all of 20 minutes – easy – but at $1400 this ended up being the most expensive part of the project. The shifter assembly on a 4L60E sticks out further to the side of the transmission than a 700R4 due to the park/neutral switch. The stock K5 shifter linkage bolts right up, but I had to cut about an inch off the rod that pivots in the frame rail to make everything fit. There is no need for any aftermarket parts. I also used the late model quick connect cooler lines which fit around the LS motor a lot better than the stock K5 flared lines. Transfer Case My truck has a NP208 case. It will not bolt to the 4L60E directly. Supposedly the 241 case from a 91 will bolt to the 4L60E, but it also needs an electronic speedometer head. My 208 works fine and I didn’t want to scrounge yards and take chances on an unknown 241 and speedometer. The cable speedo in the K5 is driven from the 208 transfer case so there are no adapters needed to drive from the 4L60E. I purchased a 50-0405E adapter from Advanced Adapters to mate the 4L60 to the 208 case. This also included a speed sensor (VSS) mounted between the transmission and transfer case. The location of VSS is ideal because the PCM doesn’t care if the case is in high or low range. The stock 350/700/208 combo has a strut rod that extends from the tail of the transfer case on passengers side to one of the bellhousing bolts near the starter. With the new combo, this rod was about 3/8” too short. I solved this problem by using a long stud with washers between the rod and bellhousing. The threaded transfer case shifter rod needed to be adjusted to account for the minor change of case position relative to the shifter. Engine Mounts and Positioning This is one of the areas where I found conflicting information on various threads. Some people reported that the stock LS truck pan will clear the stock crossmember, some did not. I used Dirty Dingo adjustable LS mounts to provide as much flexibility as possible to avoid modifying the crossmember. These mounts are super nice. I set the entire engine/transmission/transfer case in the truck and the oil pan cleared the crossmember with the mounts adjusted all the way back. There was room between the cylinder heads and the firewall. The major problem was that this setup placed the transfer case about 1.5 inches further back than stock. This causes many issues: Front driveshaft would need to be lengthened and rear driveshaft shortened. My truck already had new shafts in both places, so I wasn’t going to mess with them again. Potential driveline angle vibration problems Transfer case shifter rod would have to be lenghtened or shifter moved back in floor pan Transmission shifter linkage rod in frame would need to be moved back Fan would not be centered in shroud. Power steering pump hit drivers side motor mount In order to put the engine in the stock location, the crossmember needs to be notched to clear the truck oil pan. I did not try a different oil pan because the conflict is so big I doubt it would solve the problem. There are aftermarket crossmembers available to fit LS truck pans but they reportedly require a suspension lift that my truck does not have. I notched out a section of the crossmember using an air cut off wheel. This is beefy metal and took a long time. I then flipped the cut out section over and welded it underneath the crossmember. Finally, I welded a piece of ¼” plate on the bottom of the crossmember to box it in. Due to thickness of the metal, I used a 220V stick welder instead of a 110 volt MIG. With this change, the adjustable mounts were slid forward and the engine sat in the stock position. Here's a photo of the drivers side crossmember with the engine set all the way back: Here is a photo of the setup with notch taken out of drivers side: Lessons learned: I probably could have used cheaper non-adjustable LS mounts to place motor in stock location. Also, it wasn’t until much later when I have everything hooked up and all the weight on the front end that I noticed the oil pan sump is uncomfortably close to the front differential. I can live with it since I don’t really go off road, but I would recommend using a different oil pan to anyone else doing this swap unless they have a significant suspension lift. Wiring and Computer I modified the stock Tahoe harness using the diagrams and photos on www.LT1SWAP.com. It was time consuming but really not that hard. I also sent the PCM to Brendan at LT1swap to remove VATS and reprogram. He is a great resource. The truck fired on the first crank and ran fine, for a while, but it developed a severe, intermittent rich misfire after a week of driving. Jiggling the main trunk of the harness on top of the intake manifold would make it go away for a minute. After much frustration and testing for loose connections and grounds I threw in the towel and ordered a new harness from Swap Specialties in Michigan. Lesson Leaned: I DO NOT recommend Swap Specialties. I can excuse it being delivered 4 weeks later than promised and the two incorrect connectors which they did remedy. But despite explicit instructions to build a harness with isolated ground oxygen sensors (which are standard with flex fuel engines) they sent a case ground harness. The PCM would not read the sensors. They argued that GM never made an isolated ground harness and doing it that way would fry the PCM, despite me showing them the factory diagrams, then lied about sending me a repair kit (it never came) and stopped answering emails or calls. I ended up modifying the brand new harness too. Fuel System This was easy. The AC DELCO EP381 fuel pump is an exact drop in replacement for the factory TBI pump. I ended up replacing my fuel tank and sender at the same time because the factory baffle was detached from the bottom of the tank and my gas gauge worked only sometimes. Together, these were only $150 from Rock Auto so it’s a viable option to retrofit older K5’s with the baffled in-tank pump. I also ran a heavier gauge wire from the pump connector at the tank to the fuel pump relay because I wasn’t sure if the wire to the factory low pressure TBI pump was adequately sized for the high pressure pump. I hoped to use some combination of the factory TBI and donor LS braided lines for the swap, but neither set was long enough and both would have required several adaptor fittings. I ended up using braided lines from Pure Choice Motorsports to connect the factory hard lines at the frame to the LS fuel rail. Gauges LT1SWAP programmed the PCM to drive the factory in-dash tach so that was an easy splice into the harness. An AutoMeter 2268 adaptor was used to connect the factory K5 oil pressure sender to the LS engine at the back of the intake manifold. The factory LS oil pressure sender is not needed. An AC DELCO 12551708 3-wire sensor and Standard Motors HP4440 pigtail was used to drive the K5 temperature gauge. This replaced the LS temperature sender in the drivers side head. The 3-wire sensor is for a 1998 Camaro LS1. The blue wire coming out of the pigtail was spliced to the sensor wire from the K5 harness. The other two wires were spliced into the LS harness at the sensor connector. Cooling System This was also very easy. I used the complete system from the donor Tahoe – radiator, hoses, clamps, expansion tank, and engine driven fan. The Tahoe did not have rear air conditioning, so the radiator is EXACTLY the same width as the K5 radiator. (Note: the radiator in my Suburban, which does have rear air conditioning, is much wider and would not have fit.) I carefully cut off the plastic mounting brackets from the top of the Tahoe radiator using a hacksaw. The Tahoe uses a different mount system at the bottom of the core support and the radiator is about 1.5" shorter (top to bottom). I made some cradle “feet” at the bottom of the radiator using (2) 1.5” long pieces of black 1.5” diameter ABS pipe which placed the radiator at the correct height in the K5 core support. The factory K5 shroud and top rubber isolators fit like a glove and the entire setup looks factory. The fan is half in, half out of the shroud just like it was on the 350. As a bonus, by using the Tahoe radiator you can also use the factory quick connect transmission cooler lines to the 4L60 (with some minor bending and rerouting). The Tahoe heater hoses are both are 5/8” diameter, whereas the K5 has one 5/8” and one ¾” hose. I used a Dorman adaptor and short length of ¾” heater hose to connect to the K5 heater core at the firewall. The expansion tank was mounted on the passenger side inner fender. I used some 1/8” x 1” wide aluminum stock from Home Depot to fabricate some standoffs to make the tank level. It was bolted to the inner fender using hardware from the donor truck. Note that the K5 jack handle and lug wrench, which bolted to the inner fender, are now inside the truck since they won’t fit with the coolant tank in place. Accessories Power Steering: The power steering pressure sensor on the LS steering pump needed to be removed, as it hit the engine mount and is not needed anyway. The pressure hose from the Tahoe was connected to the K5 steering box with no modifications. The Tahoe had a power steering cooler. If I had been motivated I would have made some brackets and mounted that up to the K5, but I got lazy and just cut the return line off the cooler and connected it between the LS pump and the K5 box. PCM Mount: The PCM was mounted to the drivers side fender using GM bracket P/N 15995679 ($23 from GM Parts Direct) and some leftover bolts from the Tahoe. Battery: My K5 had the battery on the passenger side. The factory Tahoe wiring harness “wanted” it to be on the drivers side, as that’s where all the power distribution takes off. I moved the battery to the drivers side using the Tahoe battery tray and mounts, and the Tahoe battery cables. I had to trim/bend/drill the Tahoe mount to get it to bolt to the core support. GM did make drivers side battery trays for squarebody trucks but it took less time (and money) to modify the Tahoe parts than search the junkyards. Alternator: Simple. Connect the thick red wide from the K5 charging harness to the stud on the back of the Tahoe alternator. Throttle Cable: The donor engine was the last year of drive by cable. The pedal end of the Tahoe cable uses the exact same bushing and end that the K5 cable did, but the Tahoe cable is longer from the firewall to the pedal. I removed the K5 pedal from the truck, put it in a vice, and bent the pedal until it matched the cable. Works perfectly. Also, the hole in the firewall needed to be enlarged a little bit using a step drill. This is MUCH easier to do without the intake manifold in place. Air Intake: Since I am running a mechanical fan with shroud, the factory Tahoe air intake pipe simply would not fit. I grudgingly purchased a cheap “cold air” intake for a 99-2006 Silverado off Ebay. The kit provided the pipe, elbow and clamps. The factory Tahoe air box, air box mounting tray/brackets/hardware and a portion of the flex connector from the Tahoe intake pipe was used in place of the 4” cone filter which I sold to a kid who put it on a Honda. I prefer the air box to the open element filter; the air box was engineered by GM to feed a 6.0 at sea level so it should be fine for a stock 5.3 a mile high. Vacuum: The K5 charcoal canister purge signal line was connected to the LS purge solenoid on top of the intake. The canister vent line was tee’d into the LS PCV line. The LS brake booster line was connected to the K5 booster using the K5 check valve. A/C: I am not running A/C since the truck goes topless from April to October. The crappy factory K5 Harrison R4 compressor is long gone from my rig. If I did want to run A/C, I would use an aftermarket high mount Sanden compressor to avoid cutting the frame for the factory low mounted LS variable displacement compressor. Also, the coolant tank would need to be moved forward a bit to leave room for the A/C line connection to the dryer. Here's everything mounted up: Exhaust This was the most difficult part. The stock 5.3 truck manifold will fit on the passenger side but hits the frame rail on the drivers side. It also “aims” the pipes outboard, since the frame rails on the Tahoe are wider than the K5. The stock 5.3 head pipe puts the single exhaust on the passenger side, which conflicts with the transfer case. Even if you notched the frame for the driver’s manifold and split the headpipes to true duals, the converter would not clear the transfer case, leaf spring shackle and drive shaft on the passenger side. Prior to starting this swap, I met with the Air Care Colorado swap inspector. He told me that some swaps that use headers have trouble passing because the catalytic converter is too far away from the engine and it does not get hot enough. So I ruled out headers. I purchased a set of 2010 Camaro SS manifolds and headpipes with catalytic converters off Ebay for about $300. These appear to be the same setup as the emissions legal GM 5.3 E-ROD crate engine. For the 5.3 E-ROD the converters are rated to a maximum GVWR of 7800 LB; the K5 GVWR is 6100. The manifolds fit the K5 perfectly. There are four catalytic converters with a short length of pipe welded in between each pair. This short pipe section lines up nicely with the K5 spring shackles. Even so, the headpipes do not bolt in directly – they are aimed wrong and the downstream oxygen sensors conflict with the spring shackles. I cut the flanges off the Camaro head pipes and welded in some of the bends cut from the Tahoe headpipes just to get the Camaro pipes to fit well enough to test fire the truck. I also moved the downstream oxygen sensor from the location between the converters to behind the back converter. Here are the headpipes after I changed the angle between manifold flange and first converter, just to get them bolted on to truck: Here's what it looked like driving to exhaust shop. Not nearly enough clearance. Given the super tight clearances and multiple bends to get pipe around the transfer case, I didn’t have the fortitude to try and run exhaust myself. I drove the truck to Boulder Muffler where Steve further adjusted the headpipes/converters and fabricated an excellent 2.5” true dual system using heavy wall pipe and turbo mufflers. With the 4 cats in place, the turbo mufflers provide a low V8 growl under power with no drone inside the cab, and the truck is virtually silent at idle – perfect for my taste. Photo after further adjustment by Boulder Muffler. Notice how nicely the spring hanger fits in between the two sections of converters. Results Power – the real reason for the swap! Brand new, the stock TBI 350 was rated at 210 HP, and who knows how much power it made after 200k. The stock 2002 5.3 is 285 HP (with single exhaust and no tune). It accelerates very nicely. It’s not muscle car fast but it doesn’t hunt for gears at every little hill on the highway. This alone is worth the swap. Smooth – the LS is so much smoother than the 350. The serpentine belt system and fan is much quieter too. Starts: It starts immediately, every time, even below zero. Clean: The Broomfield Emissions Tech Center did a very thorough visual inspection and PCM scan of the install. I provided documentation of VIN/year from the donor vehicle and of the GM cut sheet for the 5.3 E-Rod catalytic converter weight ratings. The main things they were looking for were: · At least two catalytic converters · Four oxygen sensors · Charcoal canister hooked up · PCM saying it was ready for emission testing They issued a certificate to allow emissions inspection with the 5.3. It will need to pass the test for a 2002 model year truck. I did not pay to get an actual test done, since my truck is not due for another 18 months, but the emissions test results from the Tahoe showed much cleaner exhaust than the old TBI engine.