Early on in my rebuild of Truckasaurus I realized that the LS swap was going to be the best most economical and efficient swap I could do. I set about researching all the various options and parts I would need and was surprised at the lack of concise and complete information on the web regarding these swaps. They are remarkably easy but require a lot of attention to detail and the many, many variables add up to confusion if you aren’t careful. I thought I would try and document all the research I did in one place to help those in the future as they do this swap.
I have broken the summary down into several parts:
- What engine should I choose?
- Where can I find this engine, and where should I buy it from?
- What transmission should I use?
- What about my drivelines and transfer case?
- What do I do about all the electrical? Do I reuse the harness?
- Is the cooling anything special? Can I use my stock radiator?
- What should I look for in the engine, what accessories should I expect to receive in the purchase?
- How easy is it to install? Will it fit? What about motor mounts?
I hope this is helpful, I will be posting links to the parts I purchased and where I got them as the build series progresses. I currently have 7500 miles on my swap and love it!
1.) What motor. First and foremost. Semantics. The LS name refers to the aluminum block. LQ refers to the iron block. For sake of simplicity, I will refer to all as the LS motor, with the understanding that individual motors will be described by their coding. The most popular are going to be the LQ series of LS motors. Most commonly found in the truck bodies, the LQ come in LQ9 or LQ4. These were specifically developed to bridge the gap between the small blocks common to the truck market and the big block. And they did it remarkably well….
The Gen III LS motors are very well designed, maximized and efficient. A perfect example is the 2 bolt, vs 4 bolt main argument on traditional Gen I small blocks. The gen III LS comes with a 6 bolt main. Everything they learned from 50 years of mouse motors, they applied to the revolutionary jump to the gen III LS
LQ9 vs LQ4. LQ9 only built in Michigan vs LQ4 in Michigan and Mex. If that matters to you. Also the LQ9 bumps up compression with flat top pistons. Generally and commercially known as the Vortec MAX.
Both came with 317 aluminum cathedral style heads. A great flowing head that responds well to work. Don’t be persuaded into the “more popular” LM3 heads. While they do flow better, it is at the higher RPM where we are not as concerned. We are looking for low end grunt and torque, not top end flow.
LS valve springs are a good addition to these springs, with an increased spring rate that mates nicely with certain intakes we will talk about later.
The LM7 /LM4 the LM4 being an all aluminum is also another popular option at 5.3 size. These were popular as they were often cheaper than the LQ as they were more available, but that has faded recently as more LQ’s came on the market.
The LQ is also a popular option as being a iron block and truck engine it is designed with torque and strength in mind. Not a bad baseline for our trucks. The intake is also designed with torque in mind and with a 3 ton truck, the torque is what you should be focusing on not the HP.
You are gonna find LQ9’s in Cadillacs, Silverado SS and GMC High Output. The LQ4 can be found in anything from vans to Denali’s. Basically 2002- roughly 2007 on most models.
Can range from drive by wire to drive by throttle cable. If you do pickup DBW, make sure you are also getting the pedal, TAC (Throttle Actuator Controller) and harness.
2.) Where to buy or find anywhere and everywhere. These motors were put into pretty much anything that GM built in the past 15 years. Depending on how brave you feel you can get them from every place from a junkyard to a engine supplier.
Pac Fab, Turnkey engines etc, will all sell you an engine ready to drop in with everything you need. You can also source takeouts from wrecked trucks that you can see the engine run before it is pulled.
Craigslist is also a great option. I found my engine on craigslist for $2500 with trans and everything. Although I was taking a gamble that it would work. Luckily it did
Ultra important. When you are purchasing from craigslist, junkyard etc here is a list of everything you should try and get. Some are critical some are just money savers and nice to have.
- PCM and TAC module if DBW.
- Pedal Assembly if DBW
- Headers / manifolds
- Catalytic converters with O2 sensors
- wiring harness with ALL connectors (even if you don’t plan on using it)
- AC system (might as well)
- Air Intake / MAF (save yourself $100 for the MAF alone)
- if getting trans, make sure you are getting the TC adapter / Module and the Torque Converter
Often times, these are overlooked and later on they can add up and nickel and dime you when you are finishing the build. If they are missing then you can leverage on the price quite a bit.