Daily Slideshow: LS Engine Swap Tips for a Classic Chevy

Engine Selection

An LS engine swap into your favorite classic Chevy all begins with the engine selection process. If completing a build on a tight budget, junkyards are typically filled with LS-based LM7/LQ4/LQ9 truck engines as well as various F-body cars equipped with all-aluminum LS engines that can get you going on the cheap. If looking to buy new, GM Performance Parts sells just about every iteration of LS engine, including the supercharged 6.2L LS9 motor right out of the C6 ZR1 Corvette. A really good option for most folks is GMPP's "E-Rod System" which includes all necessary engine components (ECM, wiring harness, oxygen sensors, MAF sensor, accelerator pedal, etc) along with several LS engine options that make life easy when performing a swap. Those that are looking to build their own monster LS engine need not look any further than companies such as Dart, RHS, or even GM Performance for their block and cylinder heads.

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Mounts & Accessory Drive

To get your LS engine placed correctly into your engine bay, a set of vehicle-specific motor mounts can be used. Companies such as BRP Hot Rods and Hedman Performance Group make quality LS motor mounts to fit the frame of anything from a 1955-1957 Tri-Five Chevy all the way up to the 1996 full-size B-body cars. Having the correct mounts will allow for proper clearance of other components such as oil pans, exhaust headers, and even the accessory drive setup. Speaking of accessory drive options, GM offered several different configurations depending on which vehicle the engine was installed in. Generally speaking, the Corvette accessory drive provides the most clearance front to back by placing the alternator up top and power-steering pump underneath which also gives additional clearance at the bottom of the engine, but is a bit wider up top. The F-body setup has a balancer that projects further outwards and places the alternator down low with the power-steering pump placed up top on the driver side. Of all three configurations, the truck/SUV orientation projects the furthest outward from the front of the engine, but tends to be the narrowest its alternator up high and the ps pump down low. Use this as a general guide depending on which classic Chevy your LS engine will be going into.

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Flexplate & Transmissions

Just about any transmission can be coupled to an LS engine, but there are a couple of things to consider when deciding which setup to go with. The snout on the rear of an LS crankshaft is roughly .400" shorter than that of a traditional small block/big block Chevrolet engine, so if you are going to use an older automatic  transmission such as a Powerglide, TH350/400, 700R4, or even Muncie/Borg-Warner manual tranny, be sure to choose a flexplate or flywheel from companies like TCI or Silver Sport Transmission to allow everything to play nice with each other. If you are sticking with a newer transmission that originally came mated to an LS engine (4L60e, 6L80e, T-56, etc.), nothing special needs to be done other than choosing a transmission mount for your specific vehicle. Electronically controlled transmissions can easily be setup with TCI's EZ TCU controller that takes care of all the tuning and calibration without the need of a laptop.

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Wiring & Computer

Many classic hot-rodders feel the excessive wiring and computer requirements for newer engines are a bit of a hassle, but with various companies offering plug-n-play kits, installing a new engine into a classic car has never been easier. If using a pullout engine from the wrecking yard, you can simply reuse the wiring harness and computer from the donor car. For those using a new crate engine, GM Performance offers a complete kit that includes a fuse panel, sensors, and a completely labeled wiring harness. Similarly, there are various companies offering complete ECM and wiring kits such as Holley and FiTech that give you everything you need to get your LS engine running while also offering the ability to tune various engine parameters. The market is booming with this kind of stuff, so it simply comes down to if you want a basic setup or one with all the bells and whistles.

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Fuel System

Unless you are planning to run a carburetor on your LS engine, the fuel system will need to be upgraded. The fuel-injection on LS engines requires approximately 60 psi of fuel pressure, thus requiring an electric fuel pump. There are two options for incorporating a fuel pump with one being an in-tank pump and the other being an external pump. Installation of an in-tank pump is a bit more complex, but many tanks can be retrofitted with a pump. Similarly, there are now reproduction fuel tanks available with provisions for an in-tank fuel pump. In any case, the Walbro 340 or Aeromotive 340 fuel pumps are typically well suited for an LS swap. An external fuel pump, such as the Walbro 255, makes for an easier install, but tends to be a bit noisier than an in-tank unit and has the drawback of being gravity fed from the tank. That said, a roadside fix is much easier to accomplish with an external pump. Both types of pumps work quite well and the choice typically comes down to cost. If you need a new tank in your car, why not just get an EFI-ready tank?

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Other Items of Note

There are always a few odds and ends that will change depending on which model and year vehicle is undergoing an LS swap. Oil pans can cause a bit of frustration as stock pans often do not have adequate cross member and/or ground clearance, so plan on picking up a low clearance pan. The stock cooling system on many cars can be tweaked to work with an LS, but a specialty radiator will put the inlet and outlet in the correct position to minimize hose routing while also provide superior cooling. For the exhaust system, there are basically only two bolt-on choices with one being stock exhaust manifolds that hug the block or a set of headers. Clearance typically dictates which will be used. Overall, and LS swap can be tons of fun because it gives owners a chance to breath new life and technology into older cars. The marketplace is filled with LS swap components for just about everything, so build it any way you want it!

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For help with your maintenance and repair projects, please visit our how-to section in the forum.